COMPLEX COMPOUNDS 0F 1,5-DIMETHYLTETRAZOLE AND OF THE 1-METHYL DERIVATIVES 0F DIAZOLES- AND TRlAZOLES Thesis for the Degree of Ph. D. MICHIGAN. STATE UNIVERSITY DELORES MAUREEN BOWERS .197 1 J LIBRAR y MiChigan State University This is to certify that the thesis entitled COMPLEX COMPOUNDS 0F 1,5-DIMETHYLTETRAZOLE AND OF THE l—METHYL DERIVATIVES 0F DIAZOLES AND TRIAZOLES presented by DELORES MAUREEN BOWERS has been accepted towards fulfillment of the requirements for Ph.D. degree in Chemistry % [(wd: {/zzw 1 Major professor Date 11/4/71 0-7639 (MISXCMN emplex ca 1:2,4-triazole , “1 l-Iethylpyr; i“ nitromethane Nuance spect Ere measured a horde: to Get Ema! in solu betrazoleuszilv ilidazole~silv found to be [A We was obta l“king comple tMowing soli sil11er(I) syst Perchlorate an chlorate . ABSTRACT COMPLEX COMPOUNDS OF 1,5-DIMETHYLTETRAZOLE AND OF THE l-METHYL DERIVATIVES OF DIAZOLES AND TRIAZOLES BY Delores Maureen Bowers Complex compounds of 1,5-dimethy1tetrazole, 1-methyl- 1,2,4-triazole, 1—methyl-1,2,3-triazole, 1-methylimidazole and l-methylpyrazole with silver(I) perchlorate were studied in nitromethane and acetonitrile solutions by proton magnetic resonance spectroscopy. The donor proton chemical shifts were measured as a function of the donor-acceptor mole ratio in order to determine the stoichiometry of the complexes formed in solution. The stoichiometry of the 1,5—dimethyl— tetrazole-silver(I), l—methylpyrazole-silver(I) and l-methyl— imidazole-silver(I) complexes in nitromethane solutions were found to be [Ag(Lig)2+]. In other cases, although evi— dence was obtained for the complexation reaction, the re- sulting complexes were quite insoluble in nitromethane. The following solid complexes were isolated for the triazole— Silver(I) systems: mono(1—methyl-1,2,3—triazole)silver(1) perchlorate and mono(1-methyl—1,2,4—triazole)silver(I) per— Chlorate. From the magnitudes of the proton chemical shifts for eaCh equivalent proton on the ligand molecules measured upon L—‘r fi cuplexation vi lethylpyrazole through the 2-n coordinates wit the l-methyl-l, silver ion thrc triazole probal the 3-nitrogen. Iagnitudes of 1 methyl and 5-1111 approximately through the 3—: Occurring thro The relat blsodiuru-23 n wilities of n In fact, a 11 Chemical shif Trends i nixed azole-s Salim—23 res lule ratios Employed in nitrile (D .N '(Du. - 33.1 Delores Maureen Bowers complexation with silver ions, it appears that: 1) the 1- methylpyrazole molecule coordinates with the silver ion through the 2—nitrogen, 2) the 1-methylimidazole molecule coordinates with the silver ion through the 3-nitrogen, 3) the 1-methyl-1,2,4-triazole molecule coordinates with the Silver ion through the 4-nitrogen, and 4) the 1—methyl—1,2,3— triazole probably coordinates with the silver ion through the 3-nitrogen. In the case of 1,5—dimethyltetrazole, the magnitudes of the changes in the chemical shifts of the 1— methyl and 5—methyl protons upon ligand complexation were approximately the same, therefore, coordination may occur through the 3—nitrogen or have an equal probability of occurring through 2-, 3—, and 4—nitrogen. The relative donor abilities of the azoles were studied by sodium-23 nmr. Erlich (1) has shown that the varying abilities of non-aqueous solvents to change the electron density of the sodium ion is related to the solvent's donor ability as expressed by Gutmann's (2) donor number (D.N.). In fact, a linear relationship exists between the sodium-23 chemical shift and the donor number of ten different solvents. Trends in the sodium ion electron density changes in mixed azole-solvent systems were studied by observing the sodium-23 resonance as a function of ligand to sodium ion mole ratios at ligand mole fractions of < 0.10. The solvents employed in this study were nitromethane (D.N. = 2.7), aceto— nitrile (D.N. = 14.1), acetone (D.N. = 17.0) and pyridine '(D-N. - 33.1). The relative donor abilities were observed fi 11) b8: l-nethy lethylpyrazole tetrazole . H Erlich, R. University . Gutmann, v vents. Vi cited the: Delores Maureen Bowers to be: l-methylimidazole > 1—methyl—1,2,4-triazole > 1— methylpyrazole > 1—methyl—1,2,3-triazole > 1,5—dimethyl— tetrazole. REFERENCES 1. Erlich, R. H. Doctoral Dissertation, Michigan State University, 1971. 2. Gutmann, V. Coordination Chemistry in Nonaqueous Sol— vents. Vienna: Springer-Verlag. 1968, and references cited therein. (IJHPIBXCN COMPLEX COMPOUNDS OF 1,5-DIMETHYLTETRAZOLE AND OF THE 1-METHYL DERIVATIVES OF DIAZOLES AND TRIAZOLES BY Delores Maureen\Bowers A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Chemistry 1971 The auth03 fessor A- I' P' iiroughout the :1 his lalborat friendship and Special t friend Ronald encouragement A note of male, Dr. Ri for help in ed The authc lager Laine, R patience and t final months c Financial Health of the is gratefully Finally 1 gUldanee comm‘ ACKNOWLEDGMENTS The author wishes to express her appreciation to Pro- fessor A. I. Popov for his guidance and encouragement throughout the duration of this investigation, for the use of his laboratory facilities, and most of all for the friendship and the philosophy of science which he imparted. Special thanks go to my husband, Jim, and to my good friend Ronald Erlich, for their understanding, patience, encouragement and helpful discussions. A note of thanks is also extended to Dr. Thomas Pin- navaia, Dr. Richard Bodner, Carol Fitch, and Deborah Wheaton for help in editing this manuscript. The author also wishes to thank Drs. Charles Sweeley, Roger Laine, Ray Hammond, and Walter Esselman for their patience and understanding while in their employ during the final months of this study. Financial assistance from the National Institute of Health of the Department of Health, Education, and Welfare is gratefully acknowledged and appreciated. Finally the author wishes to thank the members Of her QUidance committee for their advice and helpful discussions. ii A I. INTRODUt ll. HISTORI< A. A2011 B. Pare1 G. Sodi m‘ EXPERIu. A' Chen Nit: Acet Pyn 0the Silr SOdi TABLE OF CONTENTS Page I. INTRODUCTION . . . . . . . . . . . . . . . . . 1 II. HISTORICAL . . . . . . . . . . . . . . . . . . 3 A. Azole Nomenclature . . . . . . . . . . . . 3 B. Parent Compounds . . . . . . . . . . . . . 6 Diazoles . . . . . . . . . . . . . . . . . 6 Triazoles . . . . . . . . . . . . . . . . . 8 Tetrazoles . . . . . . . . . . . . . . . . 9 Pentazoles . . . . . . . . . . . . . . . . 10 C. General Properties . . . . . . . . . . . . 10 D. Methyl Derivatives of Azoles . . . . . . . 15 1-Methylpyrazole . . . . . . . . . . . . . 15 l—Methylimidazole . . . . . . . . . . . . . 17 1-Methyl—l,2,3—triazole . . . o . . . . . . 19 1-Methyl—1,2,4—triazole . . . . . . . . . . 19 1,5-Disubstitutedtetrazoles . . . . . . . . 20 1,5—Dimethyltetrazole . . . . . . . . 20 Pentamethylenetetrazole . . . . . . . 21 E. General Theory of NMR . . . . . . . . . . . 24 F- Complexation Studies by 1H-NMR . . . . . . 27 G. Sodium-23 NMR . . . . . . . . . . . . . . . 40 III. EXPERIMENTAL . . . . . . . . . . . . . . . . . 43 A. Chemicals . . . . . . . . . . . . . . . . . 43 Nitromethane . . . . . . . . . . . . . . . 43 Acetonitrile . . . . . . . . . . . . . . . 43 Pyridine . . . . . . . . . . . . . . . . . 44 Other Solvents . . . . . . . . . . . . . . 44 Silver Perchlorate Anhydrous . . . . . . . 4: 4 Sodium Tetraphenylborate . . . . . . ihBlE OF CONTENT 8. Sodium TetrabL Hydrazc Ligands 1:5’Dil l-Methj l-Methj lfimfir lfMECE' Solid . TABLE OF CONTENTS (Cont.) Page Sodium perchlorate . . . . . . . . . . . . 45 Tetrabutylammonium perchlorate . . . . . . 45 Hydrazoic Acid . . . . . . . . . . . . . . 46 B. Ligands . . . . . . . . . . . . . . . . . . 46 1,5-Dimethyltetrazole . . . . . . . . . . . 46 1 so oaonmauurm.a.a 3H .35 A3 .35 ”3 .33 has .33 maonmauplmelw.m.a maoumauvimald.m.a wHONMHHuumNIM.N.H oaonmaspnmalm.w.a for E E E m m “VU// \\0 Z// _ Z 4 E. 4 Mia E 8. ziix J E E Rafi Jim 5 E are J13: A5 zi.io go So i . . i . // \\Z O Amv Adv ZHHHHHO Amy Adv Z.lli.v nmJ m m /m /m m\ /s . wagonfims mHONm A Afifi .mamv AMH .mamv 6.5H no oHONmHUIm.H oaonmnmm Ho waoumaoim.d . m E Lee . Z . . ANV m10\ /U'H.H U . . i = E. has z\ /olm 3; :v m\ziilo/ A3 :9 V W n ¢ 5 it m m\ /.mw mmHONdHD .mmusuosuum oaoum may .10 39.5 obflpmnmmfioo Aw .H onsmflm AHA .mnmv 0Houmuc0mnm.e.m.m.fi 2 Zoo x/z ii in m\\ mmq0N<92mm Asa .anmv Asa .mnmv oaoumnpmurmmie.m.m.a oaonnu0UImH|v.m.m.H E E z . _ \xe/ . elz\ J. E E J.\ .3 E _ , , . 2H0 m H zio Amv mmuonamsms iil (fig. 1c -1f). Th 0.... the possible of the nitrogens on proton, and then th anoie(rig.1c), 1, triazole (Fig. 1e), are also two taut III-tetrazole (Fig. Although the IUPAC the triazoles and azole are commonly The term azole rid 18505 and reap} discovered. By the ring structures ha< ‘ volved in this worl ‘ interested in organ terized derivative: 19d to the synthes In 1858, Debu eInpirical formula Ionia to react. T this term is occa (Fig. 1c — 1f). The IUPAC nomenclature distinguishes be— tween the possible tautomeric forms by listing the position of the nitrogens on the ring, the position of the imino proton, and then the base name as follows: 1,2,3—1H-tri— azole (Fig. 1c), 1,2,3—2H—triazole (Fig. 1d), 1,2,4—1H— triazole (Fig. 1e), and 1,2,4—4H—triazole (Fig. 1f). There are also two tautomeric forms for the tetrazole: 1,2,3,4— 1H-tetrazole (Fig. 1g) and 1,2,3,4—2H—tetrazole (Fig. lb). Although the IUPAC nomenclature is normally employed for the triazoles and tetrazoles, the names pyrazole and imid- azole are commonly employed for the diazoles. B. Parent Compounds The term azole first appears in the literature in the mid 18505 and reappears as more members of the series were discovered. By the end of the century all six of the azole ring structures had been mentioned. Scientists most in— volved in this work were German, Italian, and Swedish; all interested in organic synthesis. They prepared and charac— terized derivatives of the parent azoles which, in turn, led to the synthesis and deScription of the parent azoles. Diazoles In 1858, Debus (3) discovered a compound with the empirical formula C3N2H4 when he allowed glyoxal and am— monia to react. The compound became known as glyoxaline; this term is occasionally used today. Structural assignment of the two double atthe1-, 2". 4‘. toJapp in 1882 (4: (the British equiv used today) by the Iantzsch also deve adhered polyheter one tertiary nitr The imidazole Studied of all the curence in biologi imidazole ring ap but it also plays the histamine drug In 1885, Knor: designate the 1,2-« after a comparison unsaturated ring w atoms. The differ raplacement of a to nitrogen with a te thesized and Chara family, but Buchne Preparing the pare Until recentl to occur in b10109 in; since the str 7 of the two double bonds and three single bonds with protons at the 1-, 2—, 4—, and 5-positions on the ring is credited to Japp in 1882 (4). This compound was renamed "iminazole" (the British equivalent, imidazole, which is most commonly used today) by the German chemist Hantzsch in 1888 (5). Hantzsch also developed and classified azoles as five- membered polyheteroatomic ring systems containing at least one tertiary nitrogen. The imidazole nucleus is probably the most widely studied of all the azole rings, because of its natural oc— curence in biological systems (6). Not only does the imidazole ring appear as part of the amino acid histidine, but it also plays a significant role in medicine as part of the histamine drug family. In 1885, Knorr (7) introduced the name "pyrazole" to designate the 1,2—diazole nucleus. He derived the name after a comparison with pyrrole, the five—membered double— unsaturated ring with one imino nitrogen and four carbon atoms. The difference in the basic ring structure is the replacement of a methine group (=CH—) next to the imino nitrogen with a tertiary nitrogen (=N-). Knorr also syn— thesized and characterized many members of the pyrazole family, but Buchner (8) and Balbiano (9) were credited with Preparing the parent compound, 03N2H4. Until recently (10) the pyrazole moiety was not known to occur in biological Systems. This fact is very surpris— ing since the structural isomer, imidazole, occurs frequently. host and Grandberg mreuce of the pyr ity. They found t drug industry. Ho tives in medicine because of their n and fungicidal ac on the central ne for the aryl- and In 1860 both several compounds 1,2,3-triazole. T not proposed until characterized the Dinroth and Faster Cdnpound by conden 100°. Little is knc triazole and its <5 ity. The name "tri 038333 ring by Eli Stituted 1,2,4—m‘ the ring system we ceives the credit 8 Kost and Grandberg (11) have reviewed the frequency of oc— curence of the pyrazole moiety and its chemical applicabil- ity. They found that initially it was used in the dye and drug industry. More recently the use of pyrazole deriva- tives in medicine has become more wide spread, specifically because of their new-found bacteriostatic, bacteriocidal, and fungicidal activity. Also pronounced sedative action on the central nervous system (12,13) has been demonstrated for the aryl— and alkyl—pyrazoles. Triazoles In 1860 both Zinin (14) and Hofmann (15) synthesized several compounds which were shown to be derivatives of 1,2,3—triazole. The structure of the unsaturated ring was not proposed until 1886 when Pechmann (16) prepared and haracterized the simple monocyclic triazole ring. In 1910, imroth and Fester (17) also synthesized the 1,2,3—triazole ompound by condensation of hydrazoic acid and acetylene at 00°. Little is known of the chemical nature of the 1,2,3- riazole and its derivatives, or of their biological activ- ty. The name "triazole" was first given to the equivalent 2N3H3 ring by Bladin (18), when he discovered several sub— tituted 1,2,4—triazole derivatives. His description of he ring system was not correct (19,20), but he still re— eives the credit for its discovery. All known 1,2 tically (21): this natural systems. :enbers of the ins ng formation on p azoles are useful widely studied her The most widely st 3-ethyl-1,2,4-tria Powerful than Metr int (22 ‘. Because of Bl W to include in to, . .cns containing f0 thSe {1 ' ew ring der 1892 he had isolat 25). Chemical inVe they are “UClGOphi with the position is believed to be nee in the SubSti F:I:T_______________________________i 9 All known 1,2,4—triazoles have been obtained synthe— tically (21); this ring moiety has not been detected in natural systems. Certain types of 1,2,4—triazoles, usually members of the fused ring systems, are capable of inhibiting ng formation on photographic emulsions. Some 1,2,4—tri— azoles are useful as herbicides and stimulants. The most widely studied herbicide is Amizol (3—amino—1,2,4—triazole). The most widely studied stimulant is Azoman (4—cyclohexyl— 3—ethyl-1,2,4—triazole), which is about ten times more powerful than Metrazol (pentamethylenetetrazole) as a stimu— lant (22). Tetrazole Because of Bladin's interest in the synthesis of tri— azoles, it is not surprising that in 1885 he expanded his ork to include investigations of five—membered ring sys— tems containing four nitrogen atoms (23). He proposed that hese new ring derivatives be called tetrazoles (24). By 892 he had isolated the parent 1,2,3,4—tetrazole compound (25). Chemical investigations of tetrazoles have shown that hey are nucleophilic reagents whose characteristics vary ith the position and type of substitution. This, in turn, 8 believed to be the reason for the pharmacological vari— nce in the substituted tetrazoles studied by Gross and eatherstone (1) and Stone (2). These scientists have shown that substituted te sants, depending on Ugi (26 has I noted that as early dnced, but did not pentazole derivatin at room temperature he E-dinethylaminc the authors, is ste azole's explosive 1 ties have been rep: Been PIOPOSEd or to 10 t substituted tetrazoles range from stimulants to depres- ts, depending on the position and type of substitution. Pentazoles Ugi (26) has reviewed the history of pentazole; he has ed that as early as 1893 Noelting and Michel (27) pro- ed, but did not isolate or characterize, the first tazole derivative. All known derivatives are unstable room temperature and decompose explosively except for p—dimethylaminophenylpentazole (28) which, according to authors, is stable for several hours. Because of pent— e's explosive nature, few chemical and physical proper- have been reported, and no chemical applications have n proposed or tested. C. General Properties Since each of the parent azole compounds contains one 10 hydrogen and a tertiary nitrogen giving the molecule a polarity, it is not surprising that these compounds highly associated through hydrogen bonding. This as— ation can be demonstrated by comparing the boiling ts of the azoles (b.p. > 187°) with that of 1,3-cyclo— adiene ( b.p. 40.80), a double unsaturated five—membered containing only carbon atoms (Table I). These parent as are amphoteric. They can act as acids and lose ? imino proton to stronger bases, or they may act as i by accepting a proton from stronger acids. Values of 9Ka and pKa’ for th€ Recently Hanse basic nature of the in water. They £01 between the pKa an< saturated heterocyn stant, pKal, of the the number of nitr< ofbasicity, both : thitrations, was :1,2,4-triazole > The last two membe: Showed no pronouno acid. Barlin and Ba imidazole, pyrazol 1:2.3.4~tetrazole and discussed the cations! and the a in deuterOchlorofo acetic acid, and th deuteroxide . Some investigated . A c Chloroform and tri 11 pKa and pKd for the various azoles are given in Table I. Recently Hansen et a1. (29) studied the acidic and basic nature of the azoles (with the exception of pentazole) in water. They found that a linear relationship exists between the pKa and the number of nitrogen atoms in the un— saturated heterocyclic ring. However, the protonation con- stant, pKa,, of these compounds is not a linear function of the number of nitrogens in the ring. Instead, the order of basicity, both from calorimetric experiments and from pH titrations, was observed to be: imidazole >> pyrazole : 1,2,4-triazole > 1,2,3—triazole :_1,2,3,4—tetrazole. The last two members, 1,2,3—triazole and 1,2,3,4—tetrazole, showed no pronounced signs of protonation by perchloric acid. Barlin and Batterham (30) investigated a series of .midazole, pyrazole, 1,2,3etriazole, 1,2,4—triazole, and .,2,3,4—tetrazole compounds by proton magnetic resonance ind discussed the spectra of the neutral molecules, the rations, and the anions. The neutral molecules were studied n deuterochloroform, the cations were studied in trifluoro— cetic acid,and the anions were studied in 2 g_sodium euteroxide. Some of the 1—methyl derivatives were also nvestigated. A comparison of their spectra in deutero~ hloroform and trifluoroacetic acid indicated that the midazole and 1,2,4—triazole attain cation stabilization hrough an amidinium type resonance (Fig. 2). After pro— onation of the l-methylimidazole in the 3-position, the kum “monm no VF “Que cc cc In In I qufi ENG-N omO-wVH wmeIN‘me Ohlmw NZVH‘HNU mHONMwHKfiAW w- On. @300 QCQHUQUCGQOHUWOIIMxH A flexflnonv 1 WWW-WWW cwmwwm MHHJEHOBN . me UVHAN onwnnum -QIE HQUHHHQEN MVQSOONF‘an . W3>A.Ud>a.né3nU H\Ar~Unv:: on nflsz 1:7. HOHONQ “0 dunnflhgdionlm #80 Hindus-£0 mUnNflo HQUWWNFNW n .N. @nfihfiflorfl Illlulllddld .Aefimfiv nae .«w ..HmoH .sfleo .mmmo 2 .b .Aosmflv Hem ..Eo£o oeaowoououom .b ..m .Hocflogom can .b .m .wH Hoummno .bmmH .Muow 3oz .mmoum m_napuo2 .um .mpcoomsou UHHUNUOMouom mo mcofluomom new ousuoduum one ..0GH .muogmflansm oucoflomuoucH c.¢ .Homuonmmfloz >9 .Uo ..m ._oamucm2rmuo>HHOp .momm ..Q.q .Comcomo .. . .noE m m 2 H m9 .mmmmmmmmWMUmwwmwwwowMW®WO.MHMWHBMMU one Eoum :.mo>flum>flnn muH paw oHONm©H8H= ..M .CEmEmoMm moanansm males azwmuo oaoumuuouemnuoefloumifi msfi om mamuse ogouaanone.mifingsaoosnfi nmm.H mam mH mzmmmo meowannonm.m.finasano8-fi one.» mmfinwme on Nzemeo ooommesseasaoosnfi m bNH azomvo oaoumnhmamnuoEnH HH.m emm.e moannnsm .mmH aszHo oaowmuooonmfine.m.mifi afi.m nom.m.amm.m 0H.oH com HNH mzmmuo oaoomnnonmaue.m.fi se.H nsH.H nme.m esoes\oem mm mmemo oHoumHHoanIm.m.H aw.m mmo.e nm.efi emu omuww «Zammo aHoNaeHEa an.H amm.m no.aH wwfinsmfi canoe stmmo ogoumnsm w.ov ammo oqoflpmucomoaomonm.a Amohnovv d WMMMMW QWMMMm .mMQ oMm .m.n .Q.E HmMMMWMWM ocuomaoo H‘C‘N—C H‘N + N 1 he Figure 2. A: 13 H\C N/CH3 H\C g/CHs H—IC' d—H < > H—UI Ic‘——H \g/ \N/ {a 1% l-methylimidazolium cation + H— c _ I'd—CH3 H—N + N H—N N \c/ \c/ H—c N—CH3 I <———————> I I H H 1—methyl—1,2,4—triazolium cation Figure 2. Amidinium type resonances of the pro— tonated 1-methylimidazole and 1—methyl— 1,2,4—triazole. 2-proton magnetic while those of th 0.52, and 0.64 p fected much more iated with that while the other effect of the lar was demonstrated protonation occur inium resonance the charge densit field shifts of 1 3‘P1'0ton. and the methyl-1,2,3-tria proton chemical s? 015 possible cation action were made. 1:2.3-triazole we Proton, 5—proton, for 1-methyl-1,2, for the 5—proton Sistem were not in their summary azoles in fourte Pugmire and 5“Id anionic form Mr. They appli 14 Z-proton magnetic resonance shifts downfield by 1.26 ppm, while those of the 1—, 4—, and 5—protons shift only 0.42, ).52, and 0.64 ppm respectively. The 2—position was af- kcted much more because of the full positive charge assoc- ated with that position by the amidinium type resonance, bile the other positions felt only a fraction of the ffect of the large charge density. A similar relationship as demonstrated for the 1-methyl-1,2,4—triazole, where the rotonation occurred at the 4—position producing an amid— nium resonance about the 5—position. The localization of he charge density is noted from the magnitude of the down- 'eld shifts of 1.41, 0.81, and 0.34 ppm for the 5—proton, proton, and the l—methyl protons respectively. The 1- 2thyl—1,2,3-triazole and the 1-methyl—1,2,3,4-tetrazole :oton chemical shifts were also given, but no assignments 5 possible cation stabilization or Specific site of inter— !tion were made. The downfield shifts for the l—methyl— 2,3—triazole were 0.79, 1.29, and 0.37 ppm for the 4— oton, 5-proton, and the l—methyl protons respectively; r 1-methyl—1,2,3,4—tetrazole, they were 0.90 and 0.27 ppm : the 5—proton and 1-methyl protons. Data for the pyrazole ttem were not given, but the authors did include pyrazole their summary of data for chemical shift values for les in fourteen different solvents. Pugmire and Grant (31) have also studied the cationic anionic forms of the parent azoles by using carbon-13 They applied extended Hfickel and self—consistent-field nolecnlar wavefun: explain the obser‘ relation to the c protonated and di cycles. Lynch (3 ported a linear r shifts and the pr electron densi tie D. To negate a study, derivative hydrogen were inv selected because in the case of te used in an attemn The l-methy Dedichen (33) by pyrazole. Methy synthesize this were not studied and Casoni (35) nethylpyrazole h Shifted only sli identified the ' 15 olecular wavefunctions to both the o- and n-electrons to xplain the observed shifts of the carbon-13 resonance in elation to the charge densities and bond orders of the rotonated and dissociated forms of the nitrogen hetero- ycles. Lynch (32) performed a similar experiment and re— orted a linear relationship between the carbon-13 chemical hifts and the proton chemical shifts with the Hfickel n- lectron densities of the diazoles and triazoles. D. Methyl Derivatives of Azoles To negate acidic properties of azoles used in this tudy, derivatives which did not contain a free imino ydrogen were investigated. The l—methyl derivatives were elected because of their structural simplicity. However, a the case of tetrazole, the 1,5—dimethyl derivative was sed in an attempt to determine the coordination site. leMethylpyrazole The l—methylpyrazole ligand was first synthesized by dichen (33) by reaction of methyl iodide and the parent razole.v Methyl hydrazine (34) has also been used to nthesize this ligand. The properaties of l—methylpyrazole re not studied extensively until the mid 19005. Mangini d Casoni (35) reported that the absorption spectrum of 1- thylpyrazole had an absorption maximum at 214 nm which ifted only slightly upon protonation. Zerbi and Alberti(36) entified the infrared spectrum of 1-methylpyrazole for the region from 2 1050 and 940 cm'1 650 can1 were sh of a nonosubstitu pyrazoles were al pyrazoles because 1397, 1279, em"; strong band at 75 Broadus and Pole moments of 1 when the dipole m tion of the dielec curve was not obsc the weak donor -acc and the solvent a: form weak hydroge: ring. With the dev l-methylpyrazole various solvents in this field of Elguero $3}: (3 “\al. (41). Re of thisdligand a ligand with resp Standard . 16 the region from 2000—600 cm—l. Strong bands occurring at 1050 and 940 cm_1 and a weak doublet occurring at 675 and 650 cm.1 were shown to be good indicators of the presence of a monosubstituted pyrazole ring. The 1-substituted pyrazoles were also different from other substituted pyrazoles because they contained distinctive bands at 1520, 1397, 1279, cm-1; a doublet at 1100 and 1180, and a very strong band at 755 cm_1. Broadus and Vaughan (37) subsequently studied the di- pole moments of l-methylpyrazole in nine different solvents. When the dipole moment of the azole was plotted as a func— tion of the dielectric constant of the solvents, a smooth curve was not observed. The deviations were attributed to the weak donor-acceptor interactions of l—methylpyrazole and the solvent and/or to the ability of the solvents to form weak hydrogen bonds with the 2—nitrogen of the pyrazole ing. With the development of nmr as an instrumental tool, —methylpyrazole proton magnetic resonance assignments in arious solvents were investigated. Prominent investigators n this field of study were Batterham and Bigum (38), lguero g£_gl. (39), Cola and Perotili (40), and Bystrov t al. (41). Rees and Green (42) studied the carbon-13 nmr f this ligand and reported the chemical shifts of the pure igand with reSpect to the benzene resonance an external .tandard. Although son of the l-methylpy have been reporte That the imi in several biolog little is known imidazole. 1t ha the pH of biologi and coordinates w molecules (43). vulsions in rabbi and it is lethal The l-methyl 1377 (45). Sever in Table I. Perc infrared and Rama imidazole, l—meth They also reports Plexes (47,48) wi and silver(I) nit Proton nmr s (49)- They detei azole in deutero< repOrted values < and 5-protons re: 17 Although some work has been reported on the protonation the 1-methylpyrazole (30), no coordination compounds ve been reported. leMethylimidazole That the imidazole moiety occurs in an amino acid and ,several biologically active substances is known. However, ttle is known about the biological activity of l-methyl— ddazole. It has been shown that this compound changes ,e pH of biological systems through protein interactions d coordinates with Specific receptor sites on biomacro— ilecules (43). The l—methylimidazole also produces con— lsions in rabbits when administered in doses of 45 mg/kg, d it is lethal at doses of 75 mg/kg (44). The 1-methylimidazole was first prepared by wyss in 77 (45). Several of its physical properties are listed Table I. Perchard and Novak (46) have reported the 1 for l—methyl- frared and Raman spectra from 4000—200 cm— idazole, l—methylimidazole—ds, and l—methyl—da-imidazole. ey also reported the vibrational spectra of ligand com— exes (47,48) with zinc(II) halides, copper(II) halides, d silver(I) nitrate between 4000-500 cm_1. Proton nmr studies have been conducted by Reddy §£_3£. 3)- They determined the chemical shifts of l-methylimid— ole in deuterochloroform (internal reference TMS) and Dorted values of 7.90, 7.20, and 7.39 ppm for the 2—, 4—, 1 5-protons respectively. Barlin and Batterham (30) I studied the proton acetic acid by pro tbe3-nitrogen. T donor site for the demonstrated in th 48.50-53). The 1 with silver, magn nickel, copper, z' formula [M(1-MeIz‘ charge. me, is 1 terized and ident‘ “all Powder patt Raman spectra, ma epr Spectra. Formation cor l-methylimidazole 3.00 and log k2 = [A9(1~Melz)11+] a, constants were ob PH followed by da Batman and Wang ( tion (~15.6 kcal were then able to (19.4 kcal mole“ “Sing the previou reaction . 18 tudied the protonation of 1—methylimidazole in trifluoro- cetic acid by proton nmr and found protonation to occur at he 3—nitrogen. The fact that the 3—nitrogen is a good onor site for the coordination of metal ions has been emonstrated in the investigations of solid complexes (47, ,50—53). The 1—methylimidazole complexes have been formed 'th silver, magnesium, calcium, manganese, iron, cobalt, 'ckel, copper, zinc, and cadmium ions and have the general rmula [M(1-MeIz)nm+], where n is 2, 4, or 6 and the arge, me, is 1 or 2. These complexes have been charac— rized and identified with the aid of chemical analysis, -ray powder patterns, ligand field spectra, infrared and man spectra, magnetic susceptibility measurements, and pr spectra. Formation constants for the silver(I) complexes with nethylimidazole (51,52) have been reported as log k1 = .00 and log k2 = 3.89 at 25° for the formation of lg(1eMelz)11+] and [Ag(1-MeIZ)21+] respectively. These )nstants were obtained by potentiometric measurements of {followed by data treatment using Bjerrum's method (54). uman and Wang (51) also found the heat of complex forma- on (—15.6 kcal mole—1) by calorimetric methods at 25° and re then able to determine the change in free energy 9.4 kcal mole—1) and the change in entropy (21 e.u.) by ing the previously reported formation constant for the action. The l-methyl by Dimroth and Fes salt of the paren m1912wolff (56) the 5-carboxyl-1 vestigations of undertaken. Elgu characteristics 0 including the l—m tions for the pro c511,. crscogm, an concerning coordin have been reported Pellizari and In2.4-triazole in the parent azole a and formamide. Fe triazole compound. W30 have been me: the picrate derive methyl-l,2,4-tria: 3‘Prot‘ons occurre< Picric acid. The: 4'Position to give 19 1-Methyl—1,2,3—triazole The 1—methyl—1,2,3—triazole was first prepared in 1910 dmroth and Fester (55) when they allowed the silver :of the parent triazole to react with methyl iodide. .912 Wolff (56) prepared the ligand by decarboxylating 5—carboxyl-1-methyl—1,2,3—triazole. No extensive in— ;igations of the properties of this compound have been artaken. Elguero §$;§i: (57) have investigated the nmr ‘acteristics of 1,2,3—triazole and its derivatives, .uding the 1-methyl—1,2,3—triazole. They reported posi- ,s for the proton absorptions in d6—DMSO, CDCl3, Py, . CF3C02H, and pure ligand. To date, no investigations erning coordination compounds of 1—methyl—1,2,3—triazole been reported. 1—Methyl—1,2,4—triazole Pellizari and Soldi (58) first prepared the l-methyl— -triazole in 1905 by alkylation of the sodium salt of arent azole and by heating NzN'—diformylmethylhydrazine ormamide. Few studies have been performed on this ole compound. Proton nmr absorptions in CDCl3 and have been measured and reported by Jacquier et_§l. (59); icrate derivatives have also been reported for the 1— l—1,2,4—triazole. Greatest downfield shifts of the 5— tons occurred after interaction of the ligand with C acid. Therefore, protonation probably occurs at the ition to give the l—methyl-l,2,4—triazolium cation. 1,5- 1,5-Dinethyltetrazoj synthesized and pate auoxine to react wi iiuethyltetrazole . the ligand by reacti Kaufman fill. 1,5-dinethyltetrazoi 5.30 Debyes. Some c are listed in Table the heat of formatic n: neat of formatic inns kcal mole-1“ tetrazole (55-56 kc non (532.19 kcal m: garenttetrazole (2' indicate that the 1 in the parent tet the proton magnetic ieuterochloroform 8 having two sharp pe Chmical shifts of in ‘ethyl Protons re Coordinating a 2O 1,5-Disubstitutedtetrazoles imeth ltetrazole -— The 1,5—dimethyltetrazole was first esized and patented by A. G. Knoll (60). He allowed ime to react with hydrazoic acid to produce the 1,5- hyltetrazole. In 1950, Harvill, eg_al. (61) prepared igand by reaction of methylacetamide and hydrazoic acid. Kaufman gp_§l, (62) measured the dipole moment of the imethyltetrazole and found it to be of the order of Debyes. Some other physical properties of this ligand isted in Table I. McEwan and Rigg (63) have studied eat of formation and combustion of this ligand at 25°. eat of formation of the disubstituted tetrazole i kcal mole—1) was less than that of the parent role (56.66 kcal mole-1), although the heat of combus— i532.19 kcal mole—1) was higher than that of the : tetrazole (219.03 kcal mole—1). These data seem to .te that the 1,5-dimethyltetrazole is much more stable he parent tetrazole. Markgraf e£_gl. (64) reported oton magnetic resonance spectra of this ligand in ochloroform solution (TMS as internal standard) as two sharp peaks in the ratio of 1:1 observed at al shifts of 4.05 and 2.58 ppm for the l—methyl and yl protons respectively. oordinating ability of 1,5-dimethyltetrazole has been med only once (65) in all the studies reviewed for ale systems. This seems unusual because the l-methyl— Dle (66), the 5—methyltetrazole (67), and the 1,5-disubstituted referred to as PMT have been shown tc Gross and Fee logical properties found that 1,5-din depressants; a dos acrion on the rat. Pentamethx-‘lenetetr pentamethylenetetr characterized by 5 proved Schmidt's n procedure which is Pharmaceutical Cor This synthesis cor ildrazoic acid Cal bicyclic ring corny Gross and Fe; oi . 21 ,5-disubstituted tetrazole, pentamethylenetetrazole, often ferred to as PMT (68),have been studied extensively and ve been shown to form rather strong complexes. Gross and Featherstone (1b) have measured the pharmaco— ogical properties of the 1,5—disubstituted tetrazoles and ound that 1,5—dimethyltetrazole is one of the least potent pressants; a dosage of 750 mg/kg had only slight sedative tion on the rat. entamethylenetetrazole —- The 1,5—disubstituted tetrazole, sntamethylenetetrazole (PMT),was first synthesized and laracterized by Schmidt in 1925 (69). Later Knoll im— oved Schmidt's method of preparation and patented the ocedure which is similar to that presently used by Knoll armaceutical Company (70) and Knoll Ltd. in England (71). is synthesis consists of treating cyclohexanone with drazoic acid causing ring expansion and formation of the cyclic ring compound, PMT. Gross and Featherstone in 1946 (1a) reported the armacological activity of PMT on rabbits and rats. They and the minimum convulsive does for rats was 25 mg/kg, ile the minimum lethal does was 50 mg/kg. The complex compounds of PMT have been previously 1died in this laboratory. This work has recently been nmarized in a review article (68). Complexation of PMT 1 other 1,5—cyclopolymethylenetetrazoles with such Lewis .ds as halogens, interhalogens, silver ions and n—acids e been studied in solution to determine strength of the :- and ,T-tYPe intf tion constants 0f PMT and substitutG solutions as W911 with PMT and othel 1,2-dichloroethané at 25°. FormatiOI chloride-tetrazole while those for ti less (1.4 to 2.6g equilibrium const. an aqueous medium the silver ion co: Silver salt and a CYCIOPolymethy> len methylene? . Equ ion-tetrazole int . . lormation constan aS tetracyanoethi’ trinitrobenzene , determined spectr tions at 25° . Va 1 otter systems we indicat e very wea an d the tetrazole The iodine n ha 109m complex 1 22 - and n—type interactions of the tetrazole ring. Forma— ion constants of halogen and interhalogen complexes with Tr and substituted PMT's (72,73) in carbon tetrachloride >lutions as well as formation constants of iodine complexes Lth PMT and other cyclopolymethylenetetrazoles (74) in ,2-dichloroethane were determined spectrophotometrically : 25°. Formation constant values for the iodine mono— iloride—tetrazole interaction were about 2 X 103 M_1, iile those for the iodine—tetrazole interactions were much ass (1.4 to 2.6 Mil). D'Itri and Popov (74) measured . L . . + [uilibrium constants for the reaction Ag + T2 = [Ag(Tz)2+] 1 aqueous medium at 250 by following potentiometrically is silver ion concentration in solutions containing a lver salt and a tetrazole; Tz represents the series of clopolymethylenetetrazoles (trimethylene- through hepta— thylene—). Equilibrium constant values for the silver n-tetrazole interaction were of the order of 1 x 103 g_1. rmation constant for the PMT complexes with such m—acids tetracyanoethylene, tetracyanoquinodimethane, chloranil, initrobenzene, and trinitrofluorenone (75) were also :ermined spectrophotometrically in dichloromethane solu— >ns at 25°. Values for the formation constants for the :ter systems were very small (0.06 to 1.31 Mil) and may icate very weak m—type interactions between the m—acids the tetrazole ring. The iodine monochloride—PMT solid complex was the only Dgen complex isolated and structurally characterized. Achstallographic : ac-bond between th‘ in the 4-position (1 ring? of the “tram flmre is littl« tion metal ions and for the PMT compleX' following general fl c'rn(1>u'r)4(clo4 ‘2; in isMn,Ee, Co, Cazplexes containin the perchlorate ani distorted octahedra id in a number of iecompose between 1 lfiue. However, t lossess quite diffe znsoluble in polar higher melting or d eonolex L e ‘ 5- These c 23 ystallographic study by Baenziger, §£_gl. (76) indicated bond between the iodine monochloride and the nitrogen he 4-position (next to the carbon atom on the tetrazole ) of the tetraaole ring. There is little evidence of complexation between transi- metal ions and 1,5—disubstituted tetrazoles (68) except the PMT complexes (77-81). These complexes have the owing general formulae: MII(PMT)6(C104)27 (PMT)4(ClO4)2; MII(PMT)2X27-and MII(PMT)1XZ, where ‘is Mn, Fe, Co, Ni, Cu, and Zn and x. is Cl and Br. lexes containing six PMT molecules per metal ion and perchlorate anion were shown to have an octahedral or arted octahedral structure. They are soluble in water in a number of polar nonaqueous solvents. They melt or npose between 148-2400, and most probably are ionic in :e. However, the mono-PMT complexes with metal halides ass quite different properties. These complexes are .uble in polar and nonpolar solvents. They have much er melting or decompositions points than the perchlorate exes. These differences, as well as magnetic suscepti- y and spectroscopic data, indicate that the metal halide axes are probably polymeric and contain halogen bridges force the tetrazole ring into a bridging position. 5 (32) reported a similar condition for the copper(II) -triazole chloride complex. In this case, copper(II) .re octahedrally coordinated; the ring of the triazole le acts as a bridging ligand with two adjacent nitrogens coordina forming long polyrn occur for the PMT-; knoun case where t ligand. The energy of nucleus obtained b environment of tha trons shield the n :f the field felt applied field {H0 blunt 1: ; therefc la ,- lulues or the shit iac tom One of t zation of the elec the electronegati\ Measurement of the 24 >gens coordinated to two different copper(II) ions, thus .ng long polymeric chains. If a similar structure does ' for the PMT-metal halide system, it is the first 1 case where the tetrazole ring acts as a bidentate id. E. General Theory of NMR The energy of the resonance frequency of a given ius obtained by nmr is dependent upon the electronic tonment of that nucleus. It has been shown that elec— : shield the nucleus in Such a way that the magnitude 1e field felt by the nucleus (Hn) is different from the wed field (H0) by a value known as the shielding con— (o); therefore, H = H0 (l—o) . (1) s of the shielding constant are dependent on several rs. One of the most important factors is the hybridi— n of the electronic orbitals within the molecule and lectronegativity of the groups attached to the molecule. :ement of the actual applied field or the field felt a nucleus is very difficult; therefore, a reference ,al is employed to measure the difference between the strength at which the sample nucleus (HS) and the nce nucleus (Hr) resonates: For a given nmr pr: :Hn“ when it under- in the sample or t the value of the 5 electronic environ which expressed as Expression 4 can b .3 1 Since 0 S <<< 1 e 5 : . k‘ - a S L 25 t given nmr probe, the total field felt by the nucleus when it undergoes resonance is constant (whether it is re sample or the reference). Hn is only dependent on value of the shielding constant for the particular tronic environment of the nucleus. Thus a OS <<< 1 expression 5 reduces to: e the difference in the shielding constants of the .e and the reference is known as the chemical shift and presented by the symbol, delta (5). Relationship be— the field experienced by the nucleus (Hn) and the ancy (v) in Hz is expressed by: YH n “MTV— (7) h is Planck's constant and y is the gyromagnetic a constant characteristic of the given nucleus being measured. Separa‘; tion is often mea: shift value may be The values 0: are only slightly probe “'0' The e: De Written as; 26 .ured. Separation between sample and reference absorp— 1 is often measured in Hz. Therefore, the chemical Et value may be written in terms of frequency as: 5 = o - o = -———-———— . (8) The values of vs and VI are large numbers which only slightly different in frequency from that of the be, v The expression for the chemical shift can also 0. written as: 5 : s r _ A x 106 V0 _ V0 (9) re Va is usually a fixed frequency of 40, 60, or 100 MHz proton magnetic resonance. The term delta, A, is the Eerence Vs — Vr and usually expressed in units of Hz :h allows the chemical shift value, 6, to be expressed 3pm when substituted into equation 9. Factors within the equilibrium system, other than those in the molecule itself, which affect the nucleus under urement relate to molecular interactions with solvents solutes, to paramagnetic Species, and to nuclei with 3 quadrupole moments. These factors are classified as lgnetic and paramagentic effects depending on the direc- of the total shielding and are discussed in most general which deal with nmr theory. Valuable inf interaction of mo donor-acceptor sy netic resonance. (where A and D cules and Aan chemical shift of the donor molecul tration. Since t changing between eXChange conditio when compared to lines appear. Th the concentration molecules in the : e(Illilibrium const. these lines is d the Particular sp acceptor molecule cal shift values 3115 the 1:2 compl “hm compared to resOnance is obse the acceptor mole reSonance can be 27 F. Complexation Studies by 1H-NMR Valuable information pertaining to the structure and teraction of molecular and ionic complexes in the electron nor—acceptor systems may be obtained by using proton mag— tic resonance. For the equilibrium: nA + mD = An Dm here A and D represent the acceptor and donor mole— les and Aan the donor-acceptor complex), either the emical shift of the proton nucleus on the acceptor or on e donor molecule can be studied as a function of concen— ation. Since the acceptor and donor molecules are ex— anging between the uncomplexed and complexed states, two change conditions arise. If the exchange is very slow en compared to the life time of the complex, two resonance mes appear. The areas of these lines are proportional to 3 concentration of the respective complexed and uncomplexed lecules in the system and may be used to calculate the iilibrium constants for the reaction. The position of :se lines is determined by the chemical shift values for :particular species; assuming the measured nucleus is on eptor molecule, then 6 a a A’ AD’ etc. are the chemi— AD2 ’ shift values for the free acceptor, the 1:1 complex, the 1:2 complex. However, if the exchange is very fast 1 compared to the life time of the complex, a time-averaged nance is observed. Assuming the measured nucleus is on acceptor molecule, the position of the time—averaged lance can be represented as: where a, 5, species at any 9 When the 1 stoichiometry o by applying one 1. The che tion (bobs) is of either the d mncentration i a function of th molecules while constant. 4. The re] function of the The shape c extremes: 1 . curved line. Ir the composition that represented M...— ‘k The term Aobs 5 tion 9, but rat Chemical shift plexed molecule are a. B, and y are the mole fractions of each ecies at any given time. When the latter exchange condition prevails, the oichiometry of the complex in solution can be obtained applying one of the following procedures: 1. The chemical shift of the nucleus under investiga— .on (éobs) is plotted as a function of the concentration ’either the donor or acceptor while the other reactant's Incentration is held constant. 2. The chemical shift of the nucleus under investiga— on (d ) is plotted as a function of the mole ratio of obs e donor and acceptor. 3. The relative chemical shift (A )* is plotted as obs function of the concentration of the donor or acceptor lecules while the other reactant's concentration is held nstant. 4. The relative chemical shift (Aobs) is plotted as a rction of the mole ratio of donor and acceptor. The shape of the plotted function can vary between two remes: 1. two intersecting lines or, 2. a smooth ved line. In the first case, two intersecting lines, composition of the complex in solution corresponds to : represented by the point of intersection. In the other 2 term A should not be confused with that used in equa— obs n 9, but rather equals the difference between the observed mical shift of the nucleus in the complexed and uncom- Xd : =5 -6. e molecule thus Aobs obs A case, a smooth applied to the in intersect at a po the complex in so Once the sto sirable to evalua in solution. Ha tigators to devel quotient (note th not included in librium of the ty the well-known Be troscopy (84) to the chemical shif (which undergo ra, Plexed states) as HOD, they applie fOI equilibrium c bvnmr (82) to th The value Q rep N...“— hSimilar deriva molecules are fo 29 5e, a smooth curve, an extrapolation of tangential lines plied to the initial and final portions of the curve will :ersect at a point corresponding to the composition of a complex in solution. Once the stoichiometry has been determined, it is de- rable to evaluate the formation constant of the complex solution. Hanna and Ashbaugh (83) were the first inves- lators to develop a method which gave an equilibrium >tient (note that the activity coefficient correction was .included in the derivation). They considered an equi- rium of the type expressed in Equation 11 and applied well—known Benesi-Hildebrand method of absorption spec— scopy (84) to the nmr data. Hanna and Ashbaugh considered A+D=AD (11) -)(- chemical shift of the protons on the acceptor molecule 'ch undergo rapid exchange between complexed and uncom— ed states) as being concentration dependent. In addi— . they applied data treatments similar to those used equilibrium constant determination of hydrogen bonding mr (82) to the complexation equilibrium and showed that: A A [D] Q <3 — <5 = ____.___ 5A — 5A ) 12 obs O (1 _ [D])Q g AD 0 ( ) value Q represents the quotient of the concentrations imilar derivation applies if the nuclei on the donor ecules are followed. l of reaction product helical shift of t A fan, fiche protons in the comp is the of the acceptor pro the total concentra greater than the ac be simplified to : The reciprocal for .1. - __ Ages Am This form is analog however, the cones: and file relative cl tons in the pure (:1 “my of the comp: Wit-ht may be eva 30 reaction products and reactants, 53 is the observed emical shift of the acceptor protons in the uncomplexed A cm, éobs is the observed chemical shift of the acceptor A )tons in the complexing media, 5AD is the chemical shift the acceptor protons in the pure complex AD, and [D] is a total concentration of the donor, which is always much eater than the acceptor concentration. Equation 12 can simplified to: A A [D] Q Aobs = (1 _ [D]) Q (AAD) (13) expressing the differences of 1 1 1 1 = ————————- (-———) + ———-——— ~ (14) A A Aobs AiD (Q) [D] AAD form is analogous to the Bensi—Hildebrand equation. ver, the concentration of the acceptor does not appear, the relative chemical shift value for the acceptor pro— in the pure complex, AiD’ replaces the molar absorb— ty of the complex. The value of the equilibrium ient may be evaluated from the slope of the line obtained is plotted and extrapolated to pure [T] fl It is possible unde mthe donor molecu methods. There thi shift of the accep 5:”, can be determ' leasurements on a 8 tion of the supper ratio of the suppo is quite large; th form of the measur helical shift to Two values fo Obtained and shoul result from data t lhe two reactants varied. Hanna and sisteme in which b: These are; 1. Both dono: protons (1 give sing. are recon N c Either th be greats solvent) . 3- Nmr absor overlap t versa if A second met} c"Minot for 1:1 : 31 is possible under certain conditions to study both nuclei the donor molecules and on the acceptor molecules by nmr ods. Where this is possible, the limiting chemical ft of the acceptor nuclei, 62D, and the donor nuclei, , can be determined graphically by making chemical shift urements on a series of solutions where the concentra- of the supporting reactant is varied such that the mole 'o of the supporting reactant to the measured reactant uite large; thus increasing the amount of the complexed of the measured molecules and causing the observed . . ... D A ical shift to approach its limiting value, 5AD or 5AD Two values for the equilibrium quotient can also be ined and should agree with one another. These values llt from data treatment of two experiments where each of two reactants are held constant while the other is ed. Hanna and Ashbaugh list some criteria for ideal ems in which both the donor and acceptor can be studied. 1. Both donor and acceptor molecules should contain protons (or other magnetic nuclei) which preferably give single sharp lines when the absorption spectra are recorded. 2. Either the donor or acceptor concentration should be greater than the other components (excluding solvent). 3. Nmr absorptions of the donor and solvent should not overlap the absorptions of the acceptor (or vice versa if the donor protons are being studiedS. (83) ‘Second method for the evaluation of the formation at for 1:1 acceptor-donor complexes by nmr data has also been proposec derivation on the Hamick, and Ward} expression: L [D] where A correspt and K correspom Ashbaugh . Foster ideal or that the remains constant In this method, w line is obtained and enables A0 itely dilute solu ones as does the ‘ To study com choice of an acce is a metal ion, a Should: 1. show a i donors, 2. have wel 3. be diam: tions of the mea: 32 also been proposed by Foster and Fyfe (86). They base their derivation on the optical method described by Foster, Hammick, and Wardly (87), thereby obtaining the following expression: --— + — A K 15 where A corres onds to AA - A corres onds to AA 9 obs ' o 9 AD and K corresponds to Q in the derivation by Hanna and Ashbaugh. Foster and Fyfe assume that the solutions are yAD 7A 7D ideal or that the activity coefficient quotient remains constant over the range of solutions being studied. 1 n this method, when YET XE A is plotted, a straight ine is obtained whose negative slope gives K directly 1nd enables A0 to be obtained by extrapolation to infin— .tely dilute solutions rather than to highly concentrated nes as does the Hanna and Ashbaugh method. To study complexation in solution by proton nmr, the ioice of an acceptor is quite important. If the acceptor 5 a metal ion, as is the case of this investigation, it iOUld: 1. show a fairly strong tendency to complex with weak 2. have well—defined coordination numbers, 3. be diamagnetic to eliminate magnetic field correc— ms of the measured resonances, W | 4. form salts in lo: donor prop Because the silver( as the most accept m techniques duplexes with silv and Sheppard (85) u of the silver(I) ni haene in deuterium Mturb the double Single bonds. Qui silver(I) ion comp clclohexene, Lie—c ahalogues. The 01 ihen coordinated tc fact to the strong: coordination bond. chetiicnl shifts of hexene, but-2-ene, 01‘-‘fin-contai1-u‘.ng : Silver(I) nitrate < Whining aromati Which varied with fezlatices in the tw “change of the si in the equilibrium Vere thought to be 33 4. form salts which are fairly soluble in solvents low donor properties. se the silver(I) ion best met these requirements, it he most acceptable metal ion for the study. NMR techniques have been used to study several ionic Lexes with silver(I) salts. As early as 1960, Powell ;heppard (85) used nmr to study structural properties 1e silver(I) nitrate complex with but-2-ene and cyclo- ie in deuterium oxide. The silver(I) ion seemed to irb the double bond of the olefin and not affect the .e bonds. Quinn and VanGilder (89) also studied the :r(I) ion complexes with olefins, such as cyclopentene, mexene, gig-cyclooctene, and their l—methyl substituted >gues. The olefinic protons were deshielded by 30—50 Hz coordinated to the silver(I) ion. They attributed this to the stronger o—type than n—type component of the ination bond. Schug and Martin (90) studied the proton cal shifts of aqueous silver ion complexes of cyclo— e, but—2-ene, benzene, and toluene. The nmr spectra of n-containing aqueous solutions were independent of the :(I) nitrate concentration. However, aqueous solutions .ning aromatic molecules, produced chemical shift values varied with the silver(I) nitrate concentration. Dif- es in the two Systems were explained by the rapid ge of the silver(I) ion between the different species equilibrium mixture. Species in the aromatic system Iought to be free donor, Ar; 1:1 complex, Ar-Ag+; 1:2 complex, Alf-A9: shift of the donor average of the var: cordingly. where: The weighting factr equilibrium cons tar which is not the c. 1:1 complex is the h" assuming that t‘ [MT = [Ar10 néhy plotting th the total aromatic estraight line if eonplex ([ArlT = [ zound a linear rel Shift and the tota nd toluene. They relative chemical values were 1 hl+respe '5.6 a ctively attrihnted to the ahStem to the 311 V' 34 plex, Ar-Ag§+; etc. Therefore, the observed chemical »f the donor nucleus being measured was written as an : of the various ligand environments weighted ac- [ly, wheres n éobs = .2 Xi 5i ' (16) 1:0 .ghting factors, Xi’ cannot be evaluated unless all >rium constants for the system studied are known, .5 not the case with this system. The fact that the rplex is the most predominant one may be established iming that the total aromatic concentration is given .r]T = [Ar]O + [Ar—Ag+] + [Ar—Ag§+] ————— (17) plotting the average observed chemical shift versus al aromatic concentration; this process should yield ght line if the highest complex species is the 1:1 ([Ar]T = [Ar]O + [Ar-Ag+]). Schug and Martin (90) linear relationship between the observed chemical ad the total aromatic concentration for both benzene lene. They were also able to determine the limiting a chemical shifts for the pure 1:1 complexes. These mre 15.6 and 17.1 Hz for benzene—Ag1+ and toluene— pectively when studied at 40 MHz. These shifts were ed to the transfer of electrons from the n-electron o the silver(I) ions. In addition ti studies of silver(i some stability mea: (91} have re—examii in aqueous solutior sion: .5.“ H truth is similar t( IO! 1:1 complexes, Of the 1:2 Complex K1 —. . [A1 and K2 = \ [Al In these studies, 1 “ehzene and the dor s'l uteriI) nitrate ( Centrations ‘ he . Cfie l quite inVOlve< Sim . Pllfy the expre ARKI A1 A3.K1 35 [n addition to structural information obtained by nmr as of silver(I) complexes with various organic ligands, stability measurements have been made. Foreman, et al. have re—examined the silver(I) nitrate-benzene system ueous solution by proton nmr. They derived the expres- K1A1[Do] + K1K2A2 [13012 A = (18) 1 + K1[D0] + K1K2[Do]2 is similar to that derived by Foster and Fyfe (86) :1 complexes, except they also consider the formation e 1:2 complex as well, K1 = ——JE£2L— for A + D = AD (19) [A] [D] [AD2] K2 = —-——— for AD + D = AD2 (20) [AD] [D] :se studies, Foreman et al. defined the acceptor as e and the donor as silver(I) ion, and maintained (I) nitrate concentrations in excess of benzene con- tions. When the 1:2 complex was considered, the ination of the formation constants K1 and K2 be— iite involved; therefore, several steps were taken to ?y the expression. First new terms were defined as: = K1 A1 A2 * KiKz A2 (21) - K1 A4 = K1K2 i and subsets" A llotof — V5 P D0 — when only the 1:1 K27“) the gradi function: Thenmr data, in aleast square cu A1: and A2 are less complex, For and 0.48 kg mole- shift values for respectively whe Deb et a1 . tion between sil donors in aceton 8dilution to incl Shown that silve 94L When aceto silver(I) ion co sumed to be in t Thus the folloWi Systems studied: 36 d substituted into Equation 18 and re—arranged to give: A E)— = A1 +A2 [D0] -A3 A -A4[D0] A . (22) plot of %_ XE A gives a straight line of gradient —K1 0 an only the 1:1 complex is present, K2 = 0. However, if # 0 the gradient of the plot is given by a complex iction: A d(Do ) dDo T = A2 — A4 A (if) "' A3 "‘ A4 D0 0 (23) : nmr data, in such cases where K2 # O, are treated by ,east square curve fitting computer program, and K1, K2, and A2 are evaluated. In the silver(I) nitrate—ben- e complex, Foreman et al. (91) obtained values of 2.30 0.48 kg mole_1 for K1 and K2 and limiting chemical ft values for pure [Angzl+] and [AgZB22+] of 26 and 51 Hz Pectively when measured at 100 MHz. Deb et al. (92) used proton nmr to study complex forma— n between silver(I) ions and nitrogen, oxygen, and sulfur ors in acetonitrile. They modified the Hanna-Ashbaugh ation to include solvent effects. Several workers have fin that silver nitrate is complexed by acetonitrile (93, - When acetonitrile is in large excess as compared to Jer(1) ion concentrations, all silver(I) ions are as- id to be in the 1:2, silver(I) ion-acetonitrile complex. 5 the following equilibrium was considered for the donor :ems studied: where S repres represents amp the donors (indo holal concentrat expression: . _1_ = E An KAC for the determin ”A and 1113 wer solvent and A0 cal shift for th Shift of the pur Observed ch these heterocyc calculation of the calculated different sites information was of localized in Re-arrang (5-1-0 )octa—2 , 5 Sites 1-4) prot technique (95) - 37 A82 + D = DAS+S (24) are S represents solvent molecules (acetonitrile), A presents acceptor (silver(I) ions), and D represents . donors (indol, benzofuran, and benzothiophene). Using _al concentration units, they derived the following >ression: 1 ms 1 1 2 —=—<—>+—<1——> <25) A0 KAC ‘ mA Ac ‘ K the determination of the formation constant, K, where and mS were the molal concentrations of acceptor and vent and A0 and Ac were the observed relative chemi- shift for the donor and limiting relative chemical ft of the pure complex DAS for the donor protons. Observed chemical shifts of each proton environment on se heterocyclic ligands were recorded and used in the culation of equilibrium constants for each site. Although calculated equilibrium constant values varied for the ferent sites on a particular ligand molecule, valuable Drmation was obtained concerning the presence or absence localized interactions. Re—arrangement studies of the bullvalene or bicyclo- l‘0)Octa-2,5--diene (containing four equivalent proton as 1—4) protons have been studied using the spin-echo inique (95). The protons participate in rapid exchange reactions and the bonds can be dete presence of the 1 line width for t] (nearest the den] Rates of bullvale telnperature depe; and in the free 5 rent 0f bullvaler ions were present The univalex the elucidation Prestegard and binding of potas proton magnetic aE’Plied a least data to obtain (concentration e nonactin complex o=1/2 act where 6 is the 38 actions and the effect of silver(I) ion upon the olefinic rds can be detected. Rate of exchange was slowed by the :sence of the silver(I) cation. Also, the steady state re width for the two active proton sites at 2 and 3 :arest the double bonds) was increased upon complexation. es of bullvalene proton exchange were determined to be perature dependent both in the presence of silver(I) ions in the free state. Activation energy for the rearrange— t of bullvalene was shown to be higher when silver(I) s were present. The univalent potassium cation has also been used in elucidation of formation constants for ionic complexes. Stegard and Chan (96) have studied the nature of the iing Of potassium(I) ion to macotetrolide, nonactin, by :on magnetic resonance spectroscopy at 220 MHz. They Lied a least squaes curve fitting program to their nmr 1 to obtain an apparent formation constant of 7 i 2 x 104 lcentration expressed in mole fraction) for the Kl+- tctin complex. Their theoretical expression was: 1 5 = 1/2 éc{(1 + o + n) — [(1 + o +Tfi2 — 4¢] /2] (25) e 5 is the observed chemical shift stateh o is the to nor 2] is the stant centre [The stoichiomet: their experiment: They compared the We L“ with 1 lihrium constant Another now constants for do] been outlined by cal shift measur tions where the varied and the a Procedure was an Species created (the usual cond' iDo] = [A0] , th than under the librium wufi can be expressed 39 5 is the observed chemical shift in the complexed state, ¢ is the stoichiometric concentration ratio of K1+ to nonactin, n is the reciprocal of the apparent formation con- stant, K, and the stoichiometric nonactin con- centration. The stoichiometric concentration of nonactin was fixed in reir experiments and KClO4 concentration was varied.) ley compared the family of curves derived by plotting be XE ¢ with their experimental data to obtain the equi- .brium constant. Another novel method for the determination of formation nstants for donor—acceptor complexes by nmr has recently en outlined by Foster and Twiselton (97). The nmr chemi— 1 shift measurements were obtained on a series of solu— ons where the initial concentrations of the reactants are ried and the acceptor/donor ratio is always 1:1. This ocedure was employed to minimize the use of termolecular ecies created when the reaction conditions are [Do]>>>[AO] he usual conditions). Under these new conditions, 0] = [A0], the relative chemical shift is much smaller an under the previous condition, [Do]>>>[AO]. The equi- arium constant, K , for the formation of the 1:1 complex 1 be expressed as: which combined r chemical shift, becomes : A. no] Equilibrium con: Shifts, A0, W8} molal scale for a Computer curVe Informatio acceptor system Selution struct not always obta The site of in methods such as Sodium-23 sodium salts i this laborator Shift of the S 40 [AD] [A01 which combined with the usual expression for the observed :hemical shift, 5 =oe oA+ ES (SAD .(28) aecomes: A A 0 A __=KA(_-2+—). (29) A0] ‘A A0 :quilibrium constants, K, and limiting relative chemical :hifts, A0, colal scale for a series of values for [A0] and A using were evaluated on both the molar scale and .computer curve fitting program. M Information obtained from proton nmr studies on donor cceptor systems is often valuable in the elucidation of olution structure and strength of interaction, but it is ot always obtained directly from the site of interaction. he site of interaction can be studied by using more direct ethods such as sodium—23 nmr. Sodium—23 nmr is a useful tool in solvation studies of >dium salts in non—aqueous solvents. Nmr data obtained in ris laboratory (98) have recently shown that the chemical rift of the sodium—23 magnetic resonance is dependent upon cation-anion and anion interaction solvents having s MM 11. The c and iodide soluti while the chemica tetraphenylborate to within the lim to 10.3 ppm). Th using both sodium solutions in 10 d interactions were the changes in el Shown to be a res abilities of the was related to th Proposed a scale 0f the reaction ( acetonitrile, ac lethylformamide o Phosphoranide , Mded this stud 41 cation-anion and cation—solvent interactions. The cation— anion interactions were studied in a variety of non-aqueous solvents having sodium salt concentrations ranging from 0.10 to 0.50 g, The chemical shifts of the sodium thiocyanate and iodide solutions were shown to be concentration dependent, while the chemical shifts of the sodium perchlorate and tetraphenylborate solutions were not concentration dependent :0 within the limits of detectability of the instrument (up :0 i0.3 ppm). The cation—solvent interactions were studied rsing both sodium perchlorate and sodium tetraphenylborate solutions in 10 different solvents. When the cation—anion .nteractions were absent from the system under investigation, he changes in electron density around the sodium ion were :hown to be a result of solvent interactions. The varying milities of the solvents to change the electron density as related to the solvent's donor ability. Gutmann (99) moposed a Scale of donor numbers defined as the enthalpy f the reaction (Kcal mole—1) between a given solvent and ntimony pentachloride in 1,2-dichloroethane solution. These onor numbers (the enthalpy of complex formation between olute and solvent) were shown to be linear functions of he chemical shift for the sodium ion for both sodium per— hlorate and tetraphenylborate solutions in nitromethane, cetonitrile, acetone, ethyl acetate, tetrahydrofuran, di— ethylformamide, dimethylsulfoxide, pyridine, hexamethy1_ hosphoramide, and water. Herlem and Popov (97) have ex- anded this study to include some very basic solvents (liquid ammonia. 6 nine, t—butylamin manidine). The h lore negative the was saturated aque resonance; for ex 15.6 ppm; acetone, 29.8, cum = 0.72 The chemical been measured in m Phenylborate anion 0f the solvents f around the sodium( is that point at sMinn-23 resonanc “Y between the va value obtained in andItal solvatior Svlvents. When a Win ion yg the “00th curve is o The study of should give some streruns of thee 42 :liquid ammonia, ethylenediamine, ethylamine, iggrpropyl— mine, Efbutylamine, hydrazine, and 1,1,3,3-tetramethyl— manidine). The higher the donor number of the solvent the ore negative the chemical shift value (external reference as saturated aqueous sodium chloride) for the sodium-23 esonance; for example nitromethane D.N. = 2.7, 523Na = 5.6 ppm; acetone, D.N. = 17.0, 623Na = 8.56; DMSO, D.N. = 9.8, 523Na = 0.72; and Py, D.N. = 33.1, 623Na = —0.72 ppm. The chemical shift of the sodium—23 resonance has also een measured in mixed solvent systems (98) using the tetra— henylborate anion. The study demonstrates the competition f the solvents for the solvation or coordination positions round the sodium(I) ion. An iso—solvation point was defined 5 that point at which the chemical shift value of the >dium-23 resonance has reached a value 50 percent of the 1y between the value obtained in pure solvent A and the alue obtained in pure solvent B. At this point, there is requal solvation or complexation of the cation by the two >lvents. When a plot of observed chemical shift for the adium ion XE the mole fraction of one solvent is made, a moth curve is obtained. The study of the azole systems using this technique buld give some information about the relative donor rengths of these ligands. nitromethane Amine impu grade obtained an Amberlite IR rate of 1-2 ml activated with three 75 ml was 3001mm 20 cm then washed with discarded, befor The eluted nitrr tained from Bar: and fractionall The boiling poi to be 101° at 7 of100.8° (101) Acetonitrile Two liters Trade obtained III. EXPERIMENTAL A. Chemicals litromethane Amine impurities were removed from nitromethane (c.p. grade obtained from Fisher Scientific) by passing it through In Amberlite IR—120 (acid form) cation exchange resin at a rate of 1—2 ml per minute. The resin had previously been Lctivated with 75 ml of 0.1 g_hydrochloric acid followed by hree 75 ml washings of anhydrous methanol and packed into .column 20 cm long and 1 cm in diameter. The column was hen washed with about 100 ml of nitromethane, which was iSCarded, before the nitromethane to be purified was added. he eluted nitromethane was refluxed over barium oxide (ob— ained from Barium and Strontium Chemicals) for 12 hours nd fractionally distilled directly into dark storage bottles. he boiling point of the purified nitromethane was determined 3 be 1010 at 760 mm, as compared to the literature value f 100.80 (101). :etonitrile Two liters of acetonitrile (A.C.S. analyzed reagent :ade obtained from J. T. Baker Co.) were purified by 43 washing with two hydroxide soluti portions of anhy then decanted an 12 hours. It w pentoxide and fr was determined t nitrile was stor sieves until nee gyridine Pyridine (r and Bell) was dr followed by frac The boiling poi be 101° at 760 In Other Solvents M Rezigent gr this study were to use. Silver Perchlor Anhydrous °19anics) was u it was divided 0its: to ensure 44 ashing with two 300 ml portions of saturated potassium ydroxide solution followed by shaking twice with 60 gram artions of anhydrous sodium carbonate. The solvent was hen decanted and allowed to stand over calcium sulfate for 2 hours. It was then dried by refluxing over phosphorus entoxide and fractionally distilled. The boiling point as determined to be 81.00 at 750 mm. The purified aceto— itrile was stored in dark bottles over type 5A molecular ieves until needed. zridine Pyridine (reagent grade obtained from Matheson Coleman nd Bell) was dried over barium oxide by refluxing for 12 hr ollowed by fractional distillation into storage bottles. he boiling point of the dried pyridine was determined to e 1010 at 760 mm. her Solvents Reagent grade acetone and all other solvents used in is study were dried over type 5A molecular sieves prior use. lver Perchlorate Anhydrous Anhydrous silver perchlorate (obtained from Alfa In— ganics) was used without further purification. However, was divided into smaller portions and stored in a desic— tor to ensure dryness. was used without Sodium Perchlora Anhydrous s organics) was us Tetrabut lammoni Tetrabutyl method outlined amounts (0.10 no from Eastman Org dissolved in a m ammonium perchlo: tion by the addi volume of aceton crystallized fro “htil no yellow tion, about 30 m by dissolving it Perchlorate; if butylahmonium pa for 12 hours in 45 3dium Tetraphenylborate Sodium tetraphenylborate (obtained from J. T. Baker) as used without further purification. 3dium Perchlorate Anhydrous sodium perchlorate (obtained from Alfa In- rganics) was used without further purification. etrabutylammonium Perchlorate Tetrabutylammonium perchlorate was prepared by the ethod outlined by Coetzee and McGuire (102). Equivalent nounts (0.10 mole) of tetrabutylammonium iodide (obtained rom Eastman Organic Chemicals) and sodium perchlorate were issolved in a minimum amount of acetone. The tetrabutyl— onium perchlorate was precipitated from the acetone solu— 'on by the addition of 10 volumes of ice water to each lume of acetone present. The solid was isolated and re— ystallized from acetone—water mixtures several times, til no yellow iodide residue was observed. A samll por— on, about 30 mg, was tested for the presence of the iodide dissolving it in acetone and adding a solution of silver rchlorate; if no silver iodide was detected, the tetra— tYlammonium perchlorate was dried in a vacuum oven at 80° r 12 hours in the presence of phosphorus pentoxide. Hydrazoic Acid A solution by the method 0 sodium azide (2 The mixture wa bottomed flask stirrer, and was added to t and maintained centrated sulf wise to the vi of sulfuric ac' hydrazoic acid almost solid 5 benzene solutic until needed. extracting the ized sodium hyc‘ point. m: Hydra all reactions : in a well-vent: 1,5-Dimethylte‘ The 1,5—d 46 Hydrazoic Acid A solution of hydrazoic acid in benzene was prepared by the method of Braun (103) by suspending practical grade sodium azide (210 grams, 3.23 moles) in 210 ml of water. The mixture was placed in a 3—liter three-necked round— bottomed flask equipped with a dropping funnel, mechanical stirrer, and an alcohol thermometer. One liter of benzene was added to the aqueous slurry, and the mixture was cooled and maintained between 0—100 by an external ice bath. Con— centrated sulfuric acid (85 ml, 1.60 moles) was added drop- wise to the vigorously stirred slurry. When the addition of sulfuric acid was complete, the benzene layer,with hydrazoic acid dissolved in it, was decanted from the almost solid sludge of sodium sulfate. The hydrazoic acid— benzene solution was stored over anhydrous sodium sulfate until needed. The normality of the acid was determined by extracting the acid into water and titrating with standard— ized Sodium hydroxide solution to the phenolphthalein end- point. CAUTION: Hydrazoic acid vapors are highly toxic; therefore, all reactions involving this reagent should be carried out in a well-ventilated hood. B. Ligands 1,5-Dimethyltetrazole (1.5-DiMQEEl The 1,5—dimethyltetrazole was prepared by the method outlined by Mar tion medium con hydroxide solut (c (CH3)2c=N-0H ~— mole) was dissc stirred and ext ide (65 grams, of 36-40 minut chloride to th Sodium azide (A mum amount of v pension over a loved to reach mantle, and was water, was rem: residue was ob three times wi extractions wi extracts were to yield the c the reaction In the residue we acetone and we and concentrat method was the 47 outlined by Margraf, Bachmann, and Hollis (64). The reac— tion medium consisted of 345 ml of 1.0 g_aqueous sodium hydroxide solution in which acetone oxime (26 grams, 0.556 (C6H5 )sozcl NaN3 CHéc fiCH3 (CH3 )2C=N-OH NaOH > (CH3 )2C=N-Cl > ,, , mole) was dissolved. The reaction mixture was mechanically stirred and externally chilled while benzenesulfonyl chlor— ide (65 grams, 0.353 mole) was added dropwise over a period of 30-40 minutes. During the addition of benzenesulfonyl chloride to the reaction mixture, a white solid was formed. Sodium azide (24 grams, 0.353 mole) was dissolved in a mini— mum amount of water and added dropwise to the chilled sus— pension over a period of 30 minutes. The solution was al- lowed to reach room temperature, warmed slowly by a heating antle, and was refluxed for 12—15 hours. The solvent, ater, was removed under reduced pressure, and a solid esidue was obtained. This solid material was extracted hree times with 400—500 ml of hot benzene followed by two xtractions with 300 ml of hot chloroform. The solvent xtracts were combined and allowed to evaporate to dryness 0 yield the crude tetrazole. If the solid residue from he reaction mixture retained a large amount of solvent, he residue was slurried with acetone and filtered. The cetone and water filtrate was placed in an evaporating dish nd concentrated. The solid residue obtained using this ethod was then extracted as previously described. The product was rec mixture followe of 14.7 grams ( point of 71.5-i 71.8-72.6“. Th are shown in Pi Analysis : Methyl-1,2,4- The l-met} of Pellizzari ( Ten grams of 1, Co.) were diss< sodium methoxic transferred to 9ml of methyl in an ijg-prop tube was then return to room placed in an c to the high pr 48 oduct was recrystallized from a benzene—ether (40:60) xture followed by vacuum sublimation which gave a yield 14.7 grams (41%). The 1,5—DiMeTz obtained had a melting int of 71.5—72o as compared to the literature value of .8—72.6°. The infrared and nmr spectra of this compound e shown in Figures 1, 3 and 21 in Appendix II. Analysis: calc. %C, 36.72; %H, 6.18; 77h], 57.11 Found %c, 36.54; %H, 6.12; win, 56.85. deth l—1 2,4-triazole 1—Me—1,2,4—Trz The 1—methyl—1,2,4—triazole was prepared by the method Pellizzari (58) as outlined by Alkinson and Polya (104). 3 grams of 1,2,4—triazole (obtained from Aldrich Chemical .) were dissolved in a solution containing 7 grams of iium methoxide in 60 ml of methanol. The mixture was /H H\ /CH3 — N NaOCHa + CH3I c ——N ' ‘ " ' + NaI \ ¢N CH30H N\ ¢N c c I l H H nsferred to an 100 ml high pressure tube and about 1 of methyl iodide was added. The solution was cooled an isgfpropyl alcohol-dry ice bath. The pressure e was then sealed. The sealed tube was then allowed to urn to room temperature, shaken gently to ensure mixing, ced in an oil bath and heated to 120° for 2 hours. (Due the high pressure generated upon heating the reaction mixture, the re The reaction ve ture, placed in The unreacted mixture by eva concentrated mi and three 30 m1 tracts were coo recovered by fi duct (Hie-1,2, tion boiling a adark bottle this compound II. Analysis: Methyl-1 :2 23' The l-met] “Sing two difft Synthesis. The first triazole folio 133-triazole b1 decarboxyla PIepared by re and a portion 49 ixture, the reaction was carried out in a safety room.) he reaction vessel was allowed to return to room tempera— ure, placed in liquid nitrogen until frozen and opened. he unreacted triazole was removed from the yellow reaction ixture by evaporation of the methanol and extracting the oncentrated mixture with two 30 ml portions of hot benzene nd three 30 ml portions of hot chloroform. When the ex- racts were cooled, the 1,2,4—triazole precipitated and was ecovered by filtration. The residue containing the pro— uct (1—Me—1,2,4-Trz) was fractionally distilled. The frac— ion boiling at 1720 at 735 mm was collected and stored in dark bottle until used. The infrared and nmr spectra of his compound are shown in Figures 5, 7, and 22 in Appendix I. Analysis: Calc. %c, 43.35; %H, 6.08,- %N, 50.57. Found %c, 43.24; %H, 5.97; %N, 50.87. -Methyl-1,2,3—triazole fl-Me—1,2,3-Trz) The 1—methyl—1,2,3—triazole preparation was attempted :ing two different methods, each involving a two—step 'nthesis. The first method involved the preparation of 1,2,3~ iazole followed by methylation of the 1—position. The 2,3-triazole was prepared from 4—carboxy—1,2,3—triazole decarboxylation. The 4—carboyx-1,2,3—triazole (105) was ePared by refluxing propionic acid (35 grams, 0.50 mole) 3 a portion of the benzene stock solution of hydrazoic acid (page 46) This reaction flask equipped water-cooled the hood due t caped during began to separ tion mixture product was r in a well-ven hydrazoic aci and found to h 218-222". The at 220°. The distilled unde as compared t1 ‘ Attempts r the silver sa (55) or the s in methanol ( The seed bOxylation of by Pedersen l triazole, it 50 acid (page 46) equivalent to 1.5 moles of hydrazoic acid. This reaction was performed in a three—necked round—bottomed H /H H\ /H \c N c —— N _ HN3 u I —C02 n I HCICCOOH Benzene C/C\N&N Heat > H—C\NéN O O H flask equipped with a mechanical stirrer and an effective ater—cooled condenser. The reaction was carried out in the hood due to the toxicity of hydrazoic acid which es- caped during the heating process. A solid white product egan to separate after a few hours of heating. The reac- tion mixture was cooled in an ice—water bath and the solid roduct was removed by filtration. (This step was performed in a well-ventilated hood, due to the presence of unreacted hydrazoic acid.) The solid was recrystallized from water and found to have a melting or decarboxylation point at 318—222°. The 4—carboxy—1,2,3-triazole was decarboxylated it 220°. The resulting 1,2,3—triazole was then fractionally listilled under reduced pressure at a b.p. of 100° at 29 mm 6 compared to the literature value of 205-206° at 760 mm. Attempts to methylate the 1,2,3-triazole using either he silver salt of the triazole and methyl iodide in ether 55) or the sodium salt of the triazole and dimethylsulfate n methanol (106) were unsuccessful. The second method involved the preparation and decar— nylation of 1—methyl—4-carboxy—1,2,3-triazole, as reported y Pedersen (105). To prepare the 1-methyl—4-carboxy—1,2,3- riazole, it was necessary to prepare gaseous methyl azide and pass it thr of dry toluene Methyl azide ( azide (39 gram hydroxide by 0.39 mole) fr azide solution rate of libera azide was pass bubbled into through a dis per second. T' by the regulat to the sodium was added, the tional 30 mint sealed off wii allowed to st: solid formed 1 The reaction ‘ heated in boi reaction vess Precipitate v dilring the he 51 and pass it through the reaction mixture containing 100 ml of dry toluene and propiolic acid (14 grams, 0.20 mole). Methyl azide (107) was generated from a solution of sodium \ H\C N/CH3 H\C N/CH3 CH3 N3 “CO 2 HCECCOOH —-———-—> " ' _____> n I Toluene /C\\N¢§N heat C\\N¢¢N azide (39 grams, 0.60 mole) and 100 ml of 0.25 §_sodium hydroxide by the dropwise addition of dimethylsulfate (37 ml, 0.39 mole) from a graduated addition buret. The sodium azide solution was warmed to 40° in order to increase the Methyl rate of liberation of the generated methyl azide. azide was passed over anhydrous calcium chloride and then bubbled into the reaction mixture in a high pressure bottle, through a disposable Pasteur pipette at a rate of 2 bubbles per second. The rate of methyl azide evolution was adjusted by the regulation of the rate of addition of dimethylsulfate to the sodium azide solution. After all the dimethylsulfate was added, the sodium azide solution was heated for an addi— tional 30 minutes before the toluene reaction mixture was sealed off with a pinch clamp. The toluene solution was allowed to stand overnight at room temperature. A white Solid formed on the inner surface of the reaction vessel. The reaction vessel, a high pressure bottle, was sealed and heated in boiling water for 2 hours. After cooling the reaction vessel in ice water, the seal was removed, and the precipitate was filtered. Since the mixture had charred iuring the heating process, the product was dissolved in hot toluene and tr crude product recrystallized (1.8 grams, 0. repeated with heating of the 8.4 grams of t tions of the l The l-me by heating 5—1 equipped with flask was heat taining molten dioxide ceased pressure, b.p. of this coupon pendix II . Analysis : Hiethylimidaz The l—met Co.) was vacuu liquid. The :i shown as Figui Analysis: 52 toluene and treated with Norit-A decolorizing carbon. The crude product was recovered from the hot filtrate and then recrystallized from water. A white crystalline material (7.8 grams, 0.094 mole) was isolated. The preparation was repeated with the omission of the last step, sealing and heating of the pressure bottle. The latter method yielded 8.4 grams of the triazole. Therefore, all further prepara— tions of the ligand omitted the heating step. The 1-methyl—4—carboxy-1,2,3—triazole was decarboxylated by heating 5-10 grams portions in a round—bottomed flask equipped with a distillation head and a receiver. The flask was heated to 2450 by lowering it into a beaker con- taining molten WOod's metal. Once the evolution of carbon dioxide ceased, the product was distilled under reduced pressure, b.p. 140° at 20 mm. The infrared and nmr spectra of this compound are shown as Figures 9, 11, and 23 in Ap- pendix II. Analysis: Calc. %C, 43.35; %H, 6.08; %N, 50.57. Found %c, 43.25; %H, 5.88; %N, 50.44. l-Methylimidazole (1-MeIZ2 The 1-methylimidazole (obtained from Aldrich Chemical CO-) was vacuum distilled at 630 at 6 mm to give a colorless liquid, The infrared and nmr spectra of this compound are Shown as Figures 17, 19, and 25 in Appendix II. Analeis: Calc. %c, 58.50; %H, 7.38; %N, 34.12. Found %C, 58.28; %H, 7.28; flN, 33.94. pyrazole (obtai tion by using t hreaction mixt mole), potassiu (10 ml), and wa flask equipped stirred until of methyl iodid mere added drop mixture was re! was extracted 1 tions of ether The extracts we duct was fracti mole) of lddeP: determined to 1 tra of this con Appendix 11. Analysis : 53 l—Methylpyrazole (1-MePz) The 1-methy1pyrazole was prepared by the methylation of pyrazole (obtained from Aldrich Chemical Co.) in the 1—posi— tion by using the method outlined by Finar and Lord (108). a reaction mixture consisting of pyrazole (15 grams, 0.22 nole), potassium hydroxide (12.4 grams, 0.22 mole), ethanol :10 ml), and water (2 ml) was warmed in a 50 ml round-bottomed flask equipped with a condenser and stirrer. The mixture was [ H H K H CH3 \ / / / C -— N KOH > \c — N CHal \c —— N + KI . " ' ethanol " ether " ' - - H N ‘ c\c/N water H C\ /N {\C/ I I I H H H tirred until homogeneous, then 50 grams (22 ml, 0.35 mole) f methyl iodide, dissolved in 20 ml of anhydrous ether, ere added dropwise during a period of 1 hour. The reaction ixture was refluxed for an additional hour. The product as extracted from the cooled mixture with two 30 ml por- ions of ether followed by two 30 ml portions of chloroform. ne extracts were combined and concentrated before the pro— JCt was fractionally distilled, yielding 9.8 grams (0.12 ale) 0f 1-MePz. The boiling point of the ligand was Etermined to be 117° at 735 mm. The infrared and nmr spec— :a Of this compound are shown as Figures 13, 15, and 24 in >pendix II. Analysis: Calc. wt, 58.50; mm, 7.387 %N, 34.12- Found %c, 58.56; %H, 7.20; %N, 34.07. C. Tis(l,5-dimethylh lomo(1-methy1-1,2 tomo(1-nethy1-1,2 Each of the nitromethane solu chlorate, by the the ligand in nit sole ratio was gr Stir for an addit then isolated by With nitromethan 111th anhydrous e hours before the Observed. The in fish of the compl 13 in Appendix 11 these complexes 5 [Ag (1 , 5-Dine Analysis Analysi 54 C. Solid Compounds Isolated ,5-dimethyltetrazple)silver(I) Perchlorate 1-methyl—1,2,4-triazole)silver(I) Perchlorate 1—methyl-1,2,3—triazole)silver(I) Perchlorate Each of the above complexes was prepared in 20 ml of methane solution containing 0.01 mole of silver per— ‘ate, by the dropwise addition of a 2.0 M_solution of .igand in nitromethane. When the ligand to silver ion ratio was greater than 4:1, the solution was allowed to for an additional 15 minutes. The solid complex was isolated by filtration. The complex was washed first nitromethane to remove excess silver perchlorate then anhydrous ether. The solid was dried at 30° for several before the infrared spectra and melting points were ved. The infrared spectra obtained on a Nujol mull of of the complexes are listed in Figures 2,4,6,8,10, and Appendix II. Melting points and chemical analysis for complexes are as follows: ' ° lts at A 1,5-D MeTz Clo m.p. Opaque at 40 me [ g( l )2] 4 139-1410. Analysis: Calc. %c, 17.85; %H, 3.00; %N, 27.77. Found %C, 17.59; %H, 3.12; %N, 26.68. 0 [Ag(1—1Me—1,2,4—Trz)1]cio4 m.p. dec. ~ 285 . Analysis: Calc. %C, 12.40; %H, 1.74; %N, 14.47. Found %C, 12.30; %H, 1.70; %N, 14.68. Bis l-meth 1 No solid solutions of even when diet electric const of the complex tions containi vise addition Then the ligan was stirred fo which had form was washed wit] then with anhyi melting point 1 complex at 30° shown in Figur ysis and melti [Ag(1—MeI AnalY 55 [Ag(1%Me—1,2,3—Trz)1]ClO4 m.p. dec. ~ 230°. Analysis: Calc. %c, 12.40; %H, 1.74; %N, 14.47. Found 2c, 12.45; %H, 1.68; %N, 14.49. Bis(1—methylimidazple)silver(I) Perchlorate Bis(1—methylpyrazole)silver(I) Perchlorate No solid complexes could be isolated in nitromethane solutions of the ligands, 1—methyl- imidazole and -pyrazole even when diethylether was added in order to lower the di— electric constant of the reaction medium. Therefore, each of the complexes was prepared from absolute ethanol solu— tions containing 0.01 mole of silver perchlorate by the drop— wise addition of 2.0 M_solution of the ligand in ethanol. \ When the ligand to silver ion ratio was 4:1, the solution was stirred for an additional 15 minutes. The solid complex which had formed was isolated by filtration. The complex was washed with a small portion of absolute ethanol and then with anhydrous ether. The infrared spectrum and the nelting point of the complex were obtained after drying the 3°mPlex at 30° for several hours. The infrared spectra are 3h0Wn in Figures 14, 16, 18, and 20 in Appendix II. Anal— 1518 and melting points for the complexes are: [Ag(1-MeIz)2]ClO4 m.p. 119—119.5°. Analysis: Calc. %C, 25.86; %H, 3.26; %N, 15.08. Found %c, 25.75; %H, 3.78; %N, 15.20. [119(1-1481’ Analy obtained on a silane was use on the spectro band technique magnetic reson by linear inte bands were gen Model 4202 A fr Sodium Nuclear The majori Spectra were 01 the wideline or recorder sweep hmodel v 4310< Operating at 11 line width for order of 10 Hz Tore employed 4 reference was i 56 [Ag(1-MePz)2]ClO4 m.p. 126—1280. Analysis: Calc. %C, 25.86; %H, 3.26; %N, 15.08. Found %C, 25.68; %H, 3.24; %N, 15.06. D. Instrumentation Proton Nuclear Magnetic Resonance Spectra All the proton nuclear magnetic resonance spectra were obtained on a Varian A 56/60 D spectrometer. Tetramethyl— silane was used as an internal standard. Sweep calibration on the Spectrometer was Checked daily by employing the side— band technique (109). Several of the ligand proton nuclear magnetic resonance positions were more precisely determined by linear interpolation between two TMS sidebands. The side— bands were generated through the use of a Hewlett Packard Model 4202 A frequency oscillator (10 Hz to 1 MHz). Sodium Nuclear Magnetic Resonance SPQCtra The majority of the sodium nuclear magnetic resonance Spectra were obtained on the Varian DA-60 spectrometer in :he wideline configuration which was modified to allow the :ecorder sweep potentiometer to sweep the magnet power supply. l model V 4310C ££ unit, modified for phase detection and >perating at 15.88 MHz was employed. Because the natural .ine width for the sodium—23 resonance in water is on the mder of 10 Hz (98), standard non—spinning, 15-mm test tubes ere employed as sample tubes for the measurements. The . . ed Eference was a co—axial 8 mm tube containing saturat aqueous sodium brated by mean modulation uni of the samples the sidebands . sweep was empl three times to A saturat nitromethane, where the chem saturated aque The sodi few samples we Specialties MP the time sharir obtained is a 1 signal from thr quency as the z swept continuor ml to noise 1:: were collected 1030) until th‘ could be obser The sample was saturated aque allowed to con arid the sample 57 aqueous sodium chloride solution. The spectra were cali— brated by means of the sidebands produced by the wideline modulation unit operating at 400 Hz and the chemical shift of the samples was determined by linear interpolation from the sidebands. A sweep rate of 250 seconds (or more) per sweep was employed, and the Spectra were retraced at least three times to average the effects of field drift. A saturated solution of sodium tetraphenylborate in nitromethane, as a secondary standard, was used in cases where the chemical shift of the sample was masked by the saturated aqueous sodium chloride reference resonance. The sodium nuclear magnetic resonance Spectrum of a few samples was obtained on a Nuclear Magnetic Resonance Specialties MP 1000 pulsed nmr spectrometer operating in the time sharing mode. In this configuration, the spectrum obtained is a plot of the integrated free induction decay Signal from the sample as the ordinate yersgs the radio fre- quency as the abscissa. The spectrum appears as a frequency Swept continuous wave nmr spectrum but at a much higher sig— nal to noise ratio and at a scan rate of 20 seconds. Scans were collected on a time averaging computer (Fabri-Tek MOdel 1080) until the resonance absorption Signal 0f the sample :ould be observed on the computer's readout oscilloscope- The sample was then replaced with the reference solution of saturated aqueous sodium chloride and the computer was lllowed to continue collecting data until the reference peak 1nd the sample peak were both discernible. This spectrum was then trans was determined. setting the t' the scan length During th the instrument were made for 5 another as thes small in the c Infrared S ectr The infrar spective silver methylimidazoli the Perkin Elme region and on t eter in the 600 e‘lllipped with a sisting of thre ned 500 times a tween two 2 mm times. The rat transmittance i “In as neat liq 58 was then transferred to the recorder, and the chemical shift was determined. Calibration was obtained by accurately setting the time base of the pulse synthesizer and matching :he scan length of the recorder to the spectrometer. During the time required for one spectrum (two minutes) :he instrument drift was less than 5 Hz. No corrections were made for susceptibility changes from one sample to another as these were shown in previous work (98) to be small in the case of Na—23 studies. ' infrared Spectra The infrared Spectra of all the ligands and their re— spective silver perchlorate complexes as well as the 1— nethylimidazolium tetraphenylborate salt were obtained on :he Perkin Elmer 237 spectrometer in the 4000—650 cm—1 tegion and on the Digit Lab FTS-16 interferometric spectrom— ter in the 600—150 cm_1 region. The interferometer was .quipped with a 3 micron beam splitter. A reference, con- isting of three 2 mm thick polyethylene windows, was scan- ed 500 times and stored. The sample was then placed be— ween two 2 mm thick polyethylene windows and scanned 500 imes. The ratioed spectra were then plotted as percent ranSmittance from 600—150 cm‘l. The samples were either un as neat liquids or as Nujol mulls. A Beckman with a Beckman ated calomel e on of the l-me system in wate pH 7.00 buffer Heltin Points Melting on a FishernJo Microanalysis Microanal tical Laborato: of the Institui versity . Proton Nuclear The solut direct weighin Stock solution ting the apprc 2m1 volumetri With the apprc 59 pH Determinations A Beckman MOdel 76 expanded scale pH meter equipped with a Beckman 41263 glass electrode and a standard satur— ated calomel electrode was used to determine the changes in pH of the 1—methylimidazole and sodium tetraphenylborate system in water. The pH meter was calibrated with Beckman pH 7.00 buffer solution. Melting Points Melting points of the isolated solids were determined on a Fisher—Johns melting point apparatus. Microanalysis Microanalyses were performed by the Spang Microanaly- tical Laboratory in Ann Arbor, Michigan, and by F. M. D'Itri of the Institute of Water Resources at Michigan State Uni— versity. E. Solution Preparations Proton Nuclear Magnetic Resonance The solutions to be studied were prepared, either by direct weighing of the reactants or by preparing concentrated stock solutions of silver perchlorate and ligand and pipet— ting the appropriate amounts of each stock solution into a 2 ml volumetric flask and diluting to the reference mark with the appropriate solvent. An aliquot of this solution, 0.D. nmr tubes , reference. Th the probe tem were obtained. some times as In all ca perchlorate—1i Thus the eerie methane soluti reduction of 31‘ solutions were oration . Sodium Nuclear The solut weighing the 5‘ sodium perchlo adding the app solutions foll the solvent. Samples 1: the l-methyl 0‘ Weighing the s 60 or in some cases when precipitation occurred, an aliquot of the supernatant liquid was transferred to the standard 8 mm O.D. nmr tubes, and tetramethylsilane was added as internal reference. The samples were then allowed to equilibrate to the probe temperature of about 38° before the nmr spectra were obtained. All scans were repeated at least twice and some times as many as four times to ensure reproducibility. In all cases, except 1-methylimidazole, the silver perchlorate-ligand solutions were stable for several days. Thus the series of solutions to be measured could be pre— pared and measured on different days, if necessary, without changing the observed nmr spectra. In the case of nitro— methane solutions of l-methylimidazole, however, a slow reduction of silver ion was observed. Therefore, these solutions were prepared and measured immediately after prep— aration. Sodium Nuclear Magnetic Resonance The solutions to be studied were prepared by directly weighing the sodium salts, sodium tetraphenylborate or sodium perchlorate, into 5 ml volumetric flasks and then adding the appropriate aliquots of concentrated ligand Stock solutions followed by dilution to the reference mark with the solvent. Samples used in the determination of donor numbers of the l-methyl derivatives of the ligands were prepared by Weighing the sodium tetraphenylborate into 2 ml volumetric flasks and then were very near sonicator for stand overnight 61 flasks and then adding the pure ligand. These solutions were very near saturation, thus they were placed in a sonicator for about 10 minutes and then were allowed to stand overnight to ensure solubility. Proton Nuclea Nitrometh our study of silver ion. sesses very 1 compete with However, beca 35.9) and its perchlorate. To ensure ands reacted a was removed by molecule repre stituted tetra suited for pm: proton resonaJ coordination < felt that the With simpler Positions can aromatic , ali IV. RESULTS AND DISCUSSION Proton Nuclear Magnetic Resonance Studies in Nitromethane Nitromethane was selected as the solvent for a proton nmr study of the coordination site of azole ligands to silver ion. Gutmann (99) has shown that nitromethane pos- sesses very low donor ability. Therefore, it should not compete with the azoles in the complexation reactions. However, because of its high dielectric constant (e = 35.9) and its polarity, it is a good solvent for silver(I) perchlorate. I To ensure that in these complexation studies the lig— ands reacted as neutral molecules the acidic imino proton was removed by substitution in the 1—position. The PMT molecule represents the most throughly studied 1,5—disub- Stituted tetrazole, but this ligand is not especially suited for pmr studies due to the complexity of the methylene proton resonances (77). Therefore, in order to study the coordination of a tetrazole to silver ion by pmr, it was felt that the pentamethylene ring of PMT Should be replaced with simpler substituents. Substitution of the 1— and 5- positions can take many forms. The substituents can be aromatic, aliphatic, or mixed aromatic—aliphatic. The 62 1.5-dimethyltet the observed sir spectrum (64). cal shift. value 2.58 ppm for th These lines pro studying the do It seems r occurs through be shifted nor the coordinati case for the 5. methyl resonan methyl resonan are that coord an equal probe] gens. In these range shieldins slightly aroma the chemical s‘ be comparable. Chemical ment) of the 1 triazole, 1—me l-methylpyrazc under two cont: Varying concer 63 m—dimethyltetrazole was selected for this study because of :observed Simplicity of its proton magnetic resonance ctrum (64). Single resonance lines are observed at chemi- shift values of 4.05 ppm of the l—methyl protons and at 8 ppm for the 5-methyl protons in deuteriochloroform. se lines provide a simple and very suitable means of dying the donor—acceptor interaction in solution. It seems reasonable to assume that if coordination urs through the 2—nitrogen, the 1—methyl resonance would shifted more than the 5-methyl resonance. If, however, coordination occurs through the 4—nitrogen (as was the e for the isolated solid ICl-PMT complex), then the 5— hyl resonance absorption would Shift more than the 1— hyl resonance absorption. The remaining possibilities that coordination could occur at the 3—nitrogen or have Equal probability of occurring at the 2—, 3-, and 4-nitro— 5- In these latter cases the differences in the long Je shielding through the lenitrogen and 5—carbon by the Jhtly aromatic ring should be small, and the magnitudes of chemical shifts of 1—methyl and 5-methyl protons should :omparable. Chemical shift data (for each equivalent proton environ— :) of the ligands, 1,54dimethyltetrazole, 1—methyl‘112r4' izole, 1—methy1—1,2,3—triazole, 1—methylimida201e' and Ethylpyrazole in nitromethane solutions were obtained 2r two conditions: 1) constant ligand concentration With I ' ' ' constant silver ’lng concentration of Silver ion and 2) ion ooncentrati rents of observ methane were ma listed in Table wants. The 1,5-D1 nitromethane , < one for the 5-1 standard). W‘h constant at 0. varied from 0. to ligand mol shift of the PP!!! until it values >4.26 protons gradua Upon reversint perchlorate c the ligand co (correspondin 0.10 to 4.0). 4.20 to 4.08 2.59 ppm for At mole ratio: 1y cloudy. I was used in 64 concentration with varying ligand concentration. Assign- ts of observed chemical shifts for the ligands in nitro— hane were made on the basis of the literature values ted in Table II for these ligands in various other sol— ts. The 1,5-DiMeTz had two singlet proton resonances in romethane, one for the 1—methyl protons at 3.98 ppm and for the 5-methyl protons at 2.50 ppm (TMS as internal ndard). When the concentration of the ligand was held stant at 0.130 M_and the silver perchlorate concentration ied from 0.0120 to 1.211 M_(correSponding to a silver ion ligand mole ratioof from 0.10 to 9.32), the chemical ft of the l-methyl protons gradually increased from 4.01 until it became obscured by the solvent resonance at les >4.26 ppm. Chemical shift values of the 5-methyl tons gradually increased from 2.55 to 2.83 ppm (Table III). 1 reversing the reaction conditions, where the silver chlorate concentration was held constant at 0.101 M and ligand concentration was varied from 0.0101 to 0.406 M rreSponding to a ligand to silver ion mole ratio of from 3 to 4.0), the chemical shift gradually decreased from 3 to 4.08 ppm for the l—methyl protons and from 2.78 to 9 Ppm for the 5-methyl protons respectively (Table IV). mole ratios (Lig/Ag+) > 2.00, the solutions became slight— ‘ ' ' solutions cloudy. only the supernatant liquid of these used in the measurements. I- o: «88 . on.» I: has «a o m.p. I $6.. :2 38 “use.” no-5. .36.. on; I: «one os Jun mwfiwb goofs mm fl 7 I a a mo. 5 wag. I 5 p i on as .5 one no; i a; i 0.: 58 mm. a mo. s i z; or.” on 55 News.» 2. w 3. a. i i 03 5 scams 35 a: me. e -- -- was 5 3.; mo. w Nb. b ll Ir . S a 5 3.3% ow. w 04». N. .... o If PM. ms. Paw .wpwa 5 6 $95 ...... film/7V w/flfld flfl M/d/d. 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'IIVEED'L The proton magnetic resonance spectrum for 1rMe—1,2,4- rz in nitromethane consisted of three singlets at 3.89, .77, and 8.08 ppm from TMS with relative intensities of :1:1. The high field peak at 3.89 ppm, therefore, was as— igned to the 1—methyl protons; the peak at 7.77 ppm was ssigned to the 3-proton; and the low field peak at 8.08 ppm as assigned to the 5—proton based on literature values for his ligand shown in Table II. When the concentration of the 1-Me—1,2,4-Trz was held onstant at 0.476 M_and the silver perchlorate concentration as varied from 0.00112 to 0.972 M_(corresponding to a sil— er ion to ligand mole ratio of from 0.002 to 2.04), the hemical shift gradually increased from 3.90 to 4.06 ppm for he l-methyl protons, from 7.77 to 8.11 ppm for the 3—pro- on; and from 8.08 to 8.58 ppm for the 5—proton, (Table v). hen the reaction conditions were reversed and the silver erchlorate concentration was held constant at 0.238 M and he l-Me—1,2,4—Trz concentration was varied from 0.0577 to .730 M_(corresponding to a ligand to silver ion mole ratio E from 0.24 to 7.27), the chemical shift gradually de- ceased from 4.08 to 3.93 ppm for the l—methyl protons, from .59 to 8.26 ppm for the 3—proton, and from 8.12 to 7.88 ppm >r the 5—proton (Table VI). In all cases the complex formed in solution exceeded :8 solubility limit in nitromethane, therefore, all solu- .ons contained solid material. Only the supernatant liquid .5 used in the pmr measurements. At constant ligand 72 m.e m.osa o.e e.Hae m.m m.omm oa.o omeo.o >.m s.mse e.efl «.mma m.a «.mmm mH.o oomo.o a.aH s.owa m.om m.mom e.m m.oem mm.o mmH.o m.mH m.ama e.sm e.mfim H.w s.aam mm.o owH.o m.Hm w.ewa a.Hm e.mHm m.m H.mam ea.o mam.o o.om o.mma m.om «.mfim w.m e.mam we.o mam.o a.om a.ewa m.mm m.aHm m.oH m.mam mw.o moa.o II II II II II II so.H mme.o II II II II II II mm.H mwm.o II II II II II II me.H msm.o II II II II II II me.fi mas.o II II II II II II em.H www.o II II II II II II oo.m mum.o lam? 35 a “News 35 a Ceca A ask as}? , :Ie mIm CID «moIH soHomm .oCMCumEOHUHC CH Eouwwm opmnoHCoHom Ho>HHm pCm oHONmHHpI¢.N.HIH%CuoEIH map mo modem ooCMComoH UHumCmoE Couonm .> oHQme a {re “EFF. I'L .UCoEoHSmooE nooo new wood mos UHSvHH nCmnoCHomsm onn hHCo .osnn “ououHmHoon ooCHonCoo mCoHpCHOm HH¢* n .fl ®h¢.o H nConmCooHNHBIv.N.HIoEIHH II 0.93 II 00mm: and s0 00mm «00.0 200.0 50 mama 000.0 $00.0 0.0 «.30 8.0 300.0 w.0 Tana no.0 030.0 \IIH m.mmN no.0 0930.: HO>I~IIIWIMW MVP—aw NUIHONHH..H.\IHU.|.H\ \ N s IHI. HI\fi.F~II¢ AUCTI ,H IIIIfiflv \HIHUDU m QUCQCOQUH UIIHIIHUQFNUQE CCFs.CIL.Q 74 How Umws 003 Uflswfla uQMpMCHMQSm may maco I pCMpmcoo .ucwEwHSwmoE £000 .mscu ”wumuflaflomua wwcfimucoo mCOHuSHOm HH< 2 000.0 u 00000000 II II II II II II 00.0 000.0 II II II II II II 00.0 000.0 II II II II 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.0 0.000 00.0 000 0 0.00 0.000 0.00 0.000 0.0 0.000 00.0 000.0 0.0 0.000 0.00 0.000 0.0 0.000 00.0 000.0 0.0 0.000 0.00 0.000 0.0 0.000 00.0 000.0 0.0 0.000 0.00 0.000 0.0 0.000 00.0 000.0 II 0.000 II 0.000 II 0.000 II 000000 00:0 Nm d Nm 0 Nfl Q Nm 0 Nfl Q Nm 0 m Aflv + «\mflq NHB mI0 0I0 m000 I0.0.0I02I0 75 :oncentration when the mole ratios (Ag+/Lig) were > 0.85 and at constant silver ion concentration when the mole ratios (Lig/Ag+) were < 0.97, the amount of free 1—Me-1,2,4— Prz and soluble [Ag(1-Me—1,2,4—Trz)n1+] complex in the supernatant liquid were undetectable by pmr measurements. The proton magnetic resonance spectrum for the 10Me— L,2,3—Trz was very similar to that of the 10Me-1,2,4-Trz. 1t consisted of three singlets at 4.09, 7.52, and 7.71 ppm from TMS with relative intensities of 3:1:1. The peak at L.09 ppm was assigned to the l—methyl protons. The high field peak at 5.52 ppm was assigned to the 5-proton, and the .ow field peak at 7.71 ppm was assigned to the 4—proton >ased on literature values for this ligand shown in Table II. When the concentration of the ligand was held constant Lt 0.122 M_and the silver perchlorate concentration varied ?rom 0.00994 to 0.248 M_(corresponding to a silver ion to .igand mole ratio of from 0.08 to 2.03), the chemical shift If the l—methyl protons gradually increased from 4.12 ppm ntil it was obscured by the solvent peak at > 4'26 ppm. he results, therefore, are analogous to those observed in he 1,5-DiMeTz — Ag+ system. The Chemical shift for the 4- roton gradually increased from 7.79 to 8.08 ppm while the hemical shift for the 5—proton gradually increased from .68 to 7.96 ppm from TMS (Table VII). At Silver ion to igand mole ratios 3.0-82 the solutions contained precipi— . . eas— ate, and only the supernatant liQU1d was used for the m . . ios rements. In solutions with Silver to ligand mole rat o muAhwEmHsmwwg 03.04 CH poms mmB Uflswfla uCMHMQHGQSm msu maso .mSLu “mHMMHQHUoHQ Uwsflmusoo 0:0005000 wmwSE * l pCMpmcoo s 000.0 u 0000I0.0.0I02I0_ II 0.000 II 0.000 II 0.000 II 000000 0000 II II II II __ = 00.0 000.0* II II II II _. __ 00.0 000.0* 0.00 0.000 0.00 0.000 pqm>0Om 0000: 00.0 000.00 6 0.00 0.000 0.00 0.000 0.00 0.000 00.0 0000.0* 7 0.00 0.000 0.00 0.000 0.0 0.000 00.0 0000.0 0.00 0.000 0.00 0.000 0.0 0.000 00.0 0000.0 0.00 0.000 0.00 0.000 0.0 0.000 00.0 0000.0 0.00 0.000 0.00 0.000 0.0 0.000 00.0 0000.0 0.0 0.000 0.0 0.000 0.0 0.000 00.0 0000.0 0.0 0.000 0.0 0.000 0.0 0.000 00.0 00000.0 0m 4 0m 0 WNmN< 00 V0 00 < 00 0 000\+0< 02V mI0 mI0 000I0 000000 WT 77 )0, the l—methyl proton absorption was obscured by the ant absorption. At silver ion to ligand mole ratios 33, the amount of ligand remaining in solution was so .n either free or complexed state that it could not :tively be measured with any degree of accuracy. When the reaction conditions were reversed and the sil- >erchlorate concentration was held constant at 0.248 M : the ligand concentration was varied from 0.0244 to I g (corresponding to ligand to silver ion mole ratios 0.10 to 5.90), the observed chemical shift gradually Iased from 4.27 to 4.09 ppm for the 1—methyl protons, 8.09 to 7.89 ppm for the 4—proton, and from 7.97 to 7.77 ‘or the 5-proton (Table VIII). At constant ligand con— ation, when the mole ratio Ag+/Lig was > 1.22 and at .ant silver ion concentration, when the mole ratio Lig/Ag+ 0.98, the amount of free 1—Me—1,2,3-Trz and soluble fine—1,2,3-Trzn1+] complex in the supernatant liquid undetectable by pmr measurements. The 1-MeIz proton magnetic resonance spectrum in nitro- ne has been reported by Barlin and Batterham (30). They ned the chemical shift at 7.57 ppm to the 2-proton and 08 to the 4— and 5-protons. They did not distinguiSh en the 4— and 5—positions. We observed two singlet ances at 3.66 ppm and at 7.36 ppm with relative intensi- of 3:1. We also observed what appears as a doublet g Shoulders at 6.92 ppm (Figure 3a) with a relative Sity of about twice that of the smaller singlet peak. .mucmEmHSmmms map C0 @005 003 ©05000 HQMHMQHmQSm 0:0 waso .0550 000000m0000m mEOm Umchusoo 020005000 00039 . . * usmumqoo a 000.0 I 00000000 II 0.000 II 0.000 II 0.000 000000 0000 0.0 0.000 0.0 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.0 0.000 0.0 0 000 00.0 000.0 0.00 0.000 0.0 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.0 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.0 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.0 0.000 00.0 000.0 m 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0* 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0* II II II II II II «05.0 me.O* II II II II II II 00.0 000.0* II II II II II II 00.0 0000.0* II II II II II II 00.0 0000.0* II II II II II II om.o wwvo.o* II II II II II II 00.0 0000.0* E E E 000 mlw mum 0mol0 +0¢\00q 009 0.0.0020 (a) g l l 75 70 65 8 (ppm) Figure 3. Comparison of the pmr Spectrum of the 4— and 5—protons of a) l—MeIz and b) l—MeIz— AgClO4 system in nitromethane. 80 apparent doublet, however, was shown to consist of two lets at 6.91 and 6.93 ppm, reSpectively. Upon the addi- of silver perchlorate such that (Lig/Ag+) mole ratio i 0.05, the two triplets became well defined, as illus— ad in Figure 3b. Chemical shift values were assigned as >ws: 3.66 ppm to the 1-methyl protons, 7.36 ppm to the >ton, 6.93 ppm to the 4—proton, and 6.91 ppm to the 5— In. These results agreed with those reported for the Id in other solvents (Table II). When the concentration of the l—MeIz was held constant 333 M and the silver perchlorate concentration was d from 0.0393 to 1.180 M_(corresponding to silver ion gand mole ratios from 0.12 to 3.54), the chemical shift ally increased from 3.72 to 3.86 ppm for the 1—methyl ns, from 7.48 to 7.90 ppm for the 2—proton, from 7.02 38 ppm for the 4—proton, and from 6.94 to 7.27 ppm for proton (Table IX). When the reaction conditions were ed and the silver perchlorate concentration was held nt at 0.268 g_and the ligand concentration was varied .146 to 2.080 g (corresponding to ligand to silver le ratios from 0.51 to 7.30), the chemical shift grad— decreased from 3.84 to 3.69 ppm for the l—methyl pro— from 7.84 to 7.50 ppm for the 2—proton; from 7.25 to pm for the 4-proton; and from 7.14 to 6.95 ppm for the on (Table X). No precipitation was observed in this . Slight reduction of the silver ion was observed he solutions were prepared 1 hour before measurement or usmuwsoo 20 000.0 u 00002I00 II 0.000 II 0.000 II 0.000 II 0.000 II 000000 0000 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 1 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 8 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.0 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.0 0.000 0.0 0.000 0.0 0.000 00.0 0000.0 0.0 0.000 0.0 0.000 0.0 0.000 0.0 0.000 00.0 0000.0 000M< num~0 wumyq wumw0 00000 00000 00004 00000 «$0 mI0 000\+00 000000 “EMU mQOU a 000.0 u 00000000 IIIIIIIIIIIIIIII II 0.000 II 0.000 II 0.000 II 0.000 II 000000 0000 0.0 0.000 0.0 0.000 0.0 0.000 0.0 0.000 00.0 000.0 0.0 0.000 0.0 0.000 0.0 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.0 0.000 0.0 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.0 0.000 0.0 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.0 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.0 0.000 0.0 0.000 00.0 000.0 w 0.00 0.000 0.00 0.000 0.00 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 +0003 000 mI0 mI0 mI0 mmoI0 000zr0 83 n they were exposed for more than 10 minutes to the probe perature (~ 38°C). To minimize the effect of the reduc- n upon the data obtained, the solutions were mixed and sured immediately. This reduction was most noticeable Lig/Ag+ mole ratios > 2. The observed chemical shift values for the 1-MePz in romethane have been reported by Elquero, §t_al. (39). mical shift values of 3.81 ppm, 7.37 ppm (doublet), 6.18 (triplet), and 7.40 ppm (doublet), were assigned to the ethyl protons, and the 3—, 4—, and 5-proton respectively. observed one very sharp singlet at 3.82 ppm with a rela- e intensity of 3 as COmpared to a triplet at 6.19 ppm. absorption at 3.82 ppm was assigned to the 1-methyl pro— s and the absorption at 6.19 ppm was assigned the 4-pro— . We did not observe two distinguishable doublets as re— ted by Elquero, et_§l. but rather a broad combination of doublets whose center appeared at about 7.39 ppm as Wn in Figure 4a. These doublets were shown to be at 7.37 7.40 ppm and were assigned to the 3- and 5—protons re- ctively based on those values listed by Elquero, eE_§£. n the addition of silver perchlorate such that the g/Ag+) mole ratio was 1 0.05, the broad doublet was split o two distinct doublets (Figure 4b). When the concentration of the 1—MePz was held constant .299 M_and the silver perchlorate concentration varied 0.00494 to 0.742 g_(corresponding to silver ion to ligand '08 from 0.02 to 3.24), the chemical shift gradually (a) (b) L__, I J 8.0 7.5 7.0 8 (p p m) igure 4. Comparison of the pmr spectrum of the 3— and 5—protons of a) 1—MePz and b) 1—MePz — AgClO4 system in nitromethane. F7 85 eased from 3.85 to 4.10 ppm for the l-methyl protons, 7.36 to 7.78 ppm for the 3-proton, from 6.20 to 6.55 for the 4—proton, and from 7.78 to 7.86 ppm for the 5— on (Table XI). When the reaction conditions are re— ed and the silver perchlorate concentration was held tent at 0.223 g_while the ligand concentration was varied 0.0229 to 1.375 g (corresponding to ligand to silver nole ratios from 0.10 to 6.77), the chemical shift grad— ] decreased from 4.07 to 3.90 ppm for the 1—methyl pro— , from 7.72 to 7.47 ppm for the 3-proton, from 6.50 to ppm for the 4—proton, and from 7.81 to 7.58 ppm for S—proton (Table XII). At very low mole ratios (Lig/Ag+ < 0.30), it was very Lcult to determine the position of the 3~, 4-, and 5— )n resonances, because of the broadness of the peaks he lack of reproducibility in determining the center e absorption band within the limits of i 1 Hz on repeti- scans . The observed chemical shift, éobs’ for the individual n environments in all cases studied was a weighted ge of the ligand environments as free and complexed d. Since the usual coordination number for the silver the acceptor) is 2, the observed chemical shift can be en as the weighted sum of the following three terms: hemical shift of the free ligand, 6D, the chemical shift e 1:1 complex, 6AD’ and the chemical shift of the 1:2 ex, éADz' Therefore, 6 = QbD + 66 obs AD + yoAD2 where usmuwsoo a 000.0 u 00002r0H 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 0000.0 % 0.00 0.000 0.0 0.000 0.0 0.000 0.0 0.000 00.0 0000.0 0.0 0.000 0.0 0.000 0.0 0.000 0.0 0.000 00.0 0000.0 0.0 0.000 0.0 0.000 0.0 0.000 0.0 0.000 00.0 0000.0 0.0 0.000 0.0 0.000 0.0 0.000 0.0 0.000 00.0 0000.0 0.0 0.000 0.0 0.000 0.0 0.000 0.0 0.000 00.0 0000.0 0.0 0.000 0.0 0.000 0.0 0.000 0.0 0.000 00.0 00000.0 II 0.000 II 0.000 II 0.000 II 0.000 II 000000 0000 00 < 00 0 00 0 00 0 00 0 00 0 WNm~< IINmmmMIIIIIIIIIIIIIIIIIIIMWMI Elm Elm Elfin mmOlH mound\+m< 000000 mHHHHHHHHHHHHHHHHHHIIIIIIIIIIIIII 87 usmumsoo a 000.0 I 0000000H II 0.000 II 0.000 II 0.000 II 0.000 II 000000 0000 0.00 0.000 0.0 0.000 0.0 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.0 0.000 0.0 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.0 0.000 0.00 0.000 0.0 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 0000.0 0.00 0.000 0.00 0.000 0.00 0.000 0.00 0.000 00.0 000.0 II II II II II II 0.00 0.000 00.0 0000.0 II II II I II II 0.00 0.000 00.0 0000.0 NE Q Nm Q ”5' H III!!! [I 020 m¢ 000 + \ Nmmzr0 lljiilllf/I’ 88 and y are the mole fractions of total ligand in each 3 respectively. The observed chemical shift data for :hese systems are also shown in Tables III through XII >served relative chemical shifts, Aobs (in Hz). The :ved relative chemical shift is defined as the differ— between the observed chemical shift, éobs’ and the Lcal shift of the free ligand, 5D, A - é — 5 . (30) When the observed relative chemical shifts of each pro- anvironment for each ligand were plotted as a function 1e silver ion to ligand mole ratios, a variety of curve as were obtained (Figures 5—9). In each case illustrated Ligand concentration was held constant and the concen— .on of the silver ion was varied. The shapes of the :5 appear to be dependent on the relative strength of [onor—acceptor interaction, the nearness of the measured Ius to the reaction site, the predominant species in ion, and the limiting chemical shifts for each species lution. The extrapolation procedure outlined on page 29 can g be applied to the three systems 1,5—DiMeTz — AgClO4 fe 5), l-MeIz - AgClO4 (Figure 8), and l-MePz - AgClO4 7e 9). For each case the 1:2 complex (AD2) appears to * predominant species in solution. However, the I2,4-Trz — AgClO4 (Figure 6) and 1—Me-1,2,3-Trz - (Figure 7) systems do not indicate clearly the Figure 5. 89 Relationship between the observed relative chemi— cal shift f the protons of 1,5-dimethyltetrazole and the Ag /Lig mole ratio in nitromethane [Lig] was constant [AgClO4] was varied O 1—methyl protons O 5—methyl protons \IILI “obs 24i- 20- 90 Aq+/Lig MOLE RATIO Figure 5. h 91 Figure 6. Relationship between the observed relative chemi- cal shift of the protons on 1-methyl—1,2,4—tri- azole and the Ag+/Lig mole ratio in nitromethane [Lig] was constant [AgClO4] was varied O 1-methyl protons O 5-proton I 3—proton 92 I; l l l l I O I 2 Ag+/Lig MOLE RATIO Figure 6. I‘er‘wlfi ‘ Figure 7. 93 Relationship between the observed relative chemi- cal shift of the protons of 1-methyl-1,2,3-tri- azole and the Ag+/Lig mole ratio in nitromethane [L19] was constant [AgClO4] was varied O l-methyl protons o 5-proton I 4-proton 94 I Ag”/Lig MOLE RATIO Figure 7. l 2 Figure 8. 95 Relationship between the observed relative chem— cal shift of the protons of 1—methylimidazole and the Ag+/Lig mole ratio in nitromethane [Lig] was constant [AgClO4] was varied o 1-methyl protons (left ordinate) O 5-proton (left ordinate) o 2-proton (right ordinate) I 4-proton (right ordinate) —005 96 32- 28- 24- 20— II I l I I O I y 2 3 4 Ag /Lig MOLE RATIO Figure 8. I. 32 28 24 20 Figure 9. 97 Relationship between the observed relative chemi- cal shift of the protons of l—methylpyrazole and the Ag+/Lig mole ratio in nitromethane [Lig] was constant [AgClO4] was varied e 1-methyl protons (left ordinate) O 5-proton (left ordinate) n 3-proton (right ordinate) I 4—proton (right ordinate) 98 I I. - -24 I 2% _ .3 -2O 0 ’ O 24L -' -I6 ZOT -I2 A O N E '5' ° - e ,,, . ‘8 l2- ', .. 4 q I. (I O 8t ‘ — O O 4- ' - O- ‘ j l l l l l I O I 2 3 4 5 Ag‘VLIg MOLE RATIO Figure 9. 99 predominant Species in solution. Although there appears to be a slight break in Figure 6 at Ag+/Lig mole ratio of 0.5, corresponding to a 1:2 complex (AD2), it is tenuous at most to say that such a species exists in solution. Further support for this fact is that these data were obtained on the supernatant liquid, thus the observed chemical shifts represent not only the strength of the interaction but the solubility of the solid complex [Ag(1-Me—1,2,3-Trz)n]ClO4. The limiting relative chemical shift for the 1:2 com— plex (ADZ) and the 1:1 complex (AD) cannot be easily ob- tained from these Figure 5-9. Only in the case of 1,5-Di- MeTz could the limiting values for the 1:2 complex (AADZ) of 20 Hz for the 5-methyl protons and 17 Hz for the 1-methyl protons be obtained (Figure 5). In most cases it appears that the limiting relative chemical shift values for the complexed species in solution can be best obtained from the plots of the observed relative chemical shifts (A ) of each equivalent proton environment obs + . . for each ligand XE the Lig/Ag mole ratios (Figures 10—14). In each case illustrated, the silver ion concentration was held constant while the concentration of the ligand was . . + . . varied. At very small Lig/Ag mole ratios these figures represent infinitly dilute solutions of the complexed donor, While at large Lig/Ag+ mole ratios the predominant Species are the free donor molecules. By extrapolating the curves to Lig/Ag+ mole ratios of zero, the limiting relative chemi- cal shifts (AAD ) of the complexed species could be obtained n 100 Figure 10. Relationship between the observed relative Chemi- cal shift of the protons of 1,5—dimethyltetrazole and the Lig/Ag+ mole ratio in nitromethane [AgClO4] was constant [Lig] was varied o l—methyl protons o 5—methyl protons Il—l-‘ (Hz) AObs 101 l J 2355 Lig/Ag+ MOLE RATIO Figure 10. Figure 11. 102 Relationship between the observed relative chemi- cal shift of the protons of 1—methyl-1,2,4—tri- azole and the Lig/Ag+ mole ratio in nitromethama [A9C104] was constant and [Lig] was varied o 1-methyl protons O 5-proton n 3—proton EDIE (Hz) Aobs 32— 28" 24— 103 l I l J 1 O 2 4 O Lig/Ag MOLE RATIO Figure 11. Figure 12. Relationship between the observed relative chemi- cal shift of the protons of 1—methyl-1,2,3'trl‘ azole and the Lig/Ag+ mole ratio in nitromethane [AgClO4] was constant [Lig] was varied o l—methyl protons o 5—proton I 4—proton 105 2T 20- (Hz) Im obs L_ii l l l l l I O I 2 3 4 5 6 Liq/Ag+ MOLE RATIO Figure 12. 106 Figure 13. Relationship between the observed relative chemi- cal shift of the protons of 1—methylimidazole amfl the Lig/Ag+ mole ratio in nitromethane [AgClO4] was constant [Lig] was varied o 1-methyl protons (left ordinate) O 5-proton (left ordinate) a 2-proton (right ordinate) I 4-proton (right ordinate) (Hz) Obs A 28 24 20 107 L 4L 1 ' 4 6 8 '0 Lig /Ag" MOLE RATIO Figure 13. 28 24 20 108 Figure 14. Relationship between the observed relative chemi- cal shift of the protons of 1-methylpyrazole and the Lig/Ag+ mole ratio in nitromethane [AgClO4] was constant [Lig] was varied O l-methyl protons (left ordinate) I 5—proton (left ordinate) I 3—proton (right ordinate) a 4—proton (right ordinate) 109 F 28 28* 24 24' -20 20— -l6 §I2L _ 8 < 8- - 4 4' — O oi _ L 0 | Z 3 4 5 6 “ii/As? MOLE RATIO Figure 14. 110 for each proton environment. The limiting relative chemical shifts for the 1- and 5—methyl resonance of 1,5—DiMeTz was estimated to be 14 and 17 Hz respectively. For the l-Me— 1,2,4-Trz ligand the limiting relative chemical shifts were estimated to be 15, 29, and 42 Hz for the 1—methyl, 3-proton, and 5-proton respectively. The limiting relative chemical shift for the 1-Me—1,2,3—Trz were estimated to be 14, 25, and 18 Hz for the 1—methyl, 4—proton, and 5-proton respectively. The extrapolation procedure could not be applied to the l-MeIz — AgClO4 and 1-MePz — AgClO4 systems, because in these cases the plots go through a maximum observed relative chemi— cal shift at Lig/Ag+ mole ratios 2 2.00. These maxima may indicate that there is sufficient amount of the 1:1 complex in solution which has a different relative chemical shift value (AAD) from that of the 1:2 complex (AADZ) or that the formation constant K1 > K2. Either condition might cause the plots to deviate from the smooth curves postulated on page 28. Since these curves go through a maximum, the limit- ing chemical shift values for the different ligand positions were not clearly defined. In order to ensure that the shape of the curves obtained in Figures 5—14 were due to complexation and not just solu- tion effects, two additional types of experiments were per— formed. The solvent resonance was measured as a function of 1.5—DiMeTz concentration (from 0.2212 to 0.7112 g) and silver(I) perchlorate concentration (from 0.0504 to 0.3571 g). The solvent resonance did not vary by more than 1 Hz over 111 the concentration range for the ligand and not more than 2H2 for the concentration range of the silver(I) perchlorate (Table XIII). The effect of changing the ionic strength of the solution by addition of a noninteracting electrolyte, tetrabutylammonium perchlorate, was also studied. A series of solutions was prepared in which the concentrations of 1,5-DiMeTz and silver(I) perchlorate were held constant at 0.0249 and 0.0254 M_respectively. The concentration of the tetrabutylammonium perchlorate was varied from 0.0056 to 0.497 g. The observed resonance frequency of the 5—methyl and 1—methyl protons of the donor molecule remained essenti- ally constant. The differences between the two extreme concentrations of tetrabutylammonium perchlorate were ~ 1 Hz (Table XIV). The effect of the ionic strength was also studied for all the other ligand systems by holding the con— centration of the ligand constant at ~ 0.103 g_and varying the concentration of tetrabutylammonium perchlorate from ~ 0.01 to 0.50 M_(Tables XV through XVIII). In all cases the effect of increasing the salt concentration did not affect the ligand chemical shifts by more than 1 or 2 Hz. Similar results were obtained for the position of the sol~ vent resonance. These studies indicate that the observed chemical shifts of the ligand protons were in fact due to complexation reactions between ligand and silver(I) ions, and that Figures 5—14 are representative of the ligand— silver(I) ion interaction in solution. 112 o.mmN 0.00m II H.H0m Humm.0 0.00m «HHR.0 N.H00 0000.0 0.0mm sawm.0 0.000 0000.0 0.0mm 0000.0 0.000 000H.0 0.000 0000.0 «.000 000H.0 «.000 0000.0 0.00m 0000.0 0.0mm memm.0 1200 30 3.0: :0 mmo >_Hom voHomm «mo >.Hom NeOsHoI0.H .Osmspwfiouuflo as mumuoanoumm HO>HHm Ho OHONmuuwbahapwEHGIm.H mo coeumnusmosoo msflmmwsosfl £003 mocmsommu usm>H0m Opp mo mosum OUQMQOme ofluwsmmfi sououm .HHHN THQMB 0 0000.0 u 0000000000000000 0 0000.0 n ucmumcoomuemzfloI0.HH H.000 H.000 0000.0 0.000 0.000 0000.0 0.000 0.000 0000.0 0.000 H.000 0000.0 0.000 0.000 0000.0 m 0.000 0.000 0000.0 0.000 0.000 0000.0 0.000 0.000 0000.0 H.000 0.000 0000.0 H.0©H H.w0N II 0080 . mmoIH Amy A000 0 A000 0 00002000 .mcw:amfiouufls CH QHONmuumpahnumEflolm.H mo wGUGMCOme Gouonm 030 so Lumcmsum 00GOH mo uommmm may we mosum ®UQ0GOmmH Uflumcmmfi aouonm .>HN 00008 114 l usmumsoo z 00H.0 n ~000I0.0.HI02IH0 0.H00 0.000 0.000 0.000 II 0.H00 0.000 0.000 0.000 000.0 H.H00 0.000 0.000 0.000 000.0 H.H00 0.000 0.000 0.000 H0H.0 0.000 0.000 0.000 H.000 0000.0 0.000 0.000 0.000 0.000 0HH0.0 >_How .mlm mlm .mmOIH AEV A05 0 RE 0 “NE 0 GE 0 0030.50 .mcmnums IahnumEIH mo moocmcomOH Cowonm mooum mosmcomou oHuowmE sonoum IOHuHC C0 wcmsumfioupflc tam ®HONMHHuI0.N.H map so Lumsmnum 00:00 mo uowmmw may mo .>x anme #CMu.mCOU fl 00H.0 u HNHBI0.0.H-merH 0.H00 0.000 0.000 0.000 I: H.H00 0.000 0.000 0.000 000.0 0.H00 0.000 0.000 H.000 H00.0 5 n 0.H00 0.000 0.000 0.000 00H.0 0.000 0.000 0.000 0.000 0000.0 H.H00 0.000 0.000 0.000 00H0.0 >.HOm min Elw ,MEUIH ASV Ammv 0 Awmv 0 Aumv 0 ANmV 0 w6320.50 .msmgpmfi Ionpflc CH mcmngwfiomuflc Ucm mHONMHHpIm.N\HIH%£meIH mo mmocmcomwu Gououm map co sumconum UHGOH mo uommmm may mo %©5um wocmcommu UHumcmmE Couon . Hen wHQMB 116 pcmumcoo a 000.0 u HNHmzuHH 0.000 0.0H0 0.0H0 0.0H0 0.000 I- 0.000 0.0H0 n.0H0 0.>H0 0.000 000.0 0.000 0.0H0 0.0H0 0.0H0 0.000 000.0 0.000 0.0H0 0.0H0 0.0H0 0.000 000.0 0.000 0.0H0 0.0H0 0.0H0 0.000 0H0.0 0.000 0.0H0 0.0H0 0.0H0 0.000 000.0 0.000 n.0H0 0.0H0 0.0H0 0.000 00H.0 0.000 0.0H0 0.0H0 0.0Hv 0.000 000.0 0.000 0.0H0 0.0H0 H.0H0 0.000 000.0 .mmo >.HOm mmolH 0:0 0:0 ,ml0 Ag 35 0 35 . 0 A03 0 35 E0 0 «.082 gm .wcmnumEOHpHG CH mcmsuwfioauflc 6cm wHOvaflfiflahfiumfilfi mo mocmc0mwu couonm wzu co numcongm Uflcofl mo powmmm mgu mo hwsum mocmcomwn OHumcmmE cououm .HH>N QHQMB 117 ucmumcoo HIH 00H.0 H 3.002.: 0.000 0.H00 0.000 0.000 0.000 I: 0.000 0.000 0.000 0.000 0.000 000.0 0.000 0.000 0.000 0.000 0.000 000.0 0.000 0.000 0.000 0.000 0.000 HOH.0 0.000 0.000 0.000 0.000 0.H00 0000.0 0.000 0.000 0.000 0.000 0.H00 0HH0.0 .fl >_Hom mnv mum .mnm 0EH 0 A W :5 0 A20 0 $5 0 GE 0 E0 . 202 a .wcmsuma Ionuflc CH wcmguofiouufl: Ucm maoumummahgumfilfi mo mocmcommH couonm map co npmcmapm OHQOH mo pomwmm mgu mo wwsum wocmcomwn oflumcmmfi mononm .HHH>N manme 118 Since so many of the reaction mixtures in nitromethane contained some solid complex, the solid silver(I) perchlorate complexes with the various ligands were prepared and their compositions determined (pages 54—56). Triazole ligands formed 1:1 solid complexes whereas the diazoles and tetrazole formed 1:2 (Ag+:Lig) complexes with silver(I) perchlorate. A comparison of the infrared Spectra of the free ligands with those of the complexes leaves little doubt that the vibrational patterns of the ligands have been influenced by the presence of the silver ion (Figures 1-20, Appendix II). Reports of solid complexes for the l—methyl derivatives of diazoles and triazoles are limited to the 1-MeIz system. Reedijk (53) and Perchard and Novak (47,48) have reported solid complexes with silver salts and divalent first row transition metal ions. They propose that l-Melz coordinates to the metal ion through the 3—nitrogen. Reedijk (113) has also studied the coordination properties of the parent imidazole and pyrazole ligands with divalent metal perchlor— ates and tetrafluoroborates. Reedijk's studies indicate that neutral imidazole coordinates through the 3—nitrogen and that neutral pyrazole coordinates through the 2—nitrogen. Reimann, 3243;. (114,115) have also shown that pyrazole coordinates to first row transition metal ions through the 2—nitrogen. The mono(1,2,4—triazole)copper(II) chloride complex was Studied crystallographically bdearvis (82) (page 23). His Studies indicate that the two adjacent nitrogens are involved in coordination. It appears, however, that this is the 119 1,2,4—4H—triazole isomer whose 1— and 2—nitrogens might possess properties similar to the 3- and 4—nitrogens of the tetrazole ring: H lilac —— I‘N/S Edi —— T6) (wk/Cg?) <4>N\N/N<2> (1) ‘ (3) 1,2,4-4Hetriazole 1,2,3,4—1H—tetrazole Recently two additional crystallographic studies have been performed on tetrazole complexes. The crystal struc— ture of dichlorobis(1—methyltetrazole)zinc(II) was identi— fied by Baenziger and Schultz (116). The zinc ion is co- ordinated to the tetrazole ring and is essentially planar with the ring. A charge—transfer o—bond is formed between the zinc ion and the 4—nitrogen of the tetrazole ring. These data agree with those described for the PMT — ICl complex (page 23). In addition the crystal structure of bis[nitratobis(pentamethylenetetrazole)silver(I)] has been determined in this laboratory (117). The study indicates that a dimer is formed having two silver ions, two nitrate ions and four PMT molecules. Two of the PMT molecules act as bidentate ligands with nitrogen-silver distances of 2.541 and 2.216 X for the 3— and 4-nitrogens respectively. The other two PMT molecules act as monodentate ligands with nitrogen—silver distances of 2.238 R for the 4—nitrogen. The nitrate ion also enters into the coordination sphere of 120 the silver ion and acts as a monodentate ligand. The oxygen- silver distance was shown to be 2.422 X. This crystal struc- ture indicates that the tetrazole ring can indeed form poly— mer structures @imilar to 1,2,4—triazole as proposed in our previous study) by acting as a bridging ligand. In addition to the location of the preferred sites of interaction for metal ions, some protonation studies by pmr have been performed on the l—MeIz and lfifle—1,2,4—Trz ligands (page 12). The l—Melz has been shown to protonate at the 3-nitrogen while lfiMe—1,2,4—Trz protonates at the 4-nitrogen. These data support the conclusions of the previous authors concerning metal—ion complexes. It seems reasonable, there- fore, that our pmr measurements of the silver(I) perchlor— ate - ligand systems should indicate some selectivity for the interaction site. To identify this interaction site the following items were compared: 1) The chemical shift of the free ligand, 6D, in nitromethane solution, 2) The maximum chemical shift observed, 6C , under max the reaction conditions where [Lig] constant [AgClO4]varied’ 3) The maximum chemical shift observed, 5C, I under max the reaction conditions where [A9C1041constant [nglvaried’ 4) The average value of the maximum chemical shift ob— served minus the chemical shift of the free ligand, max + Clmax ——————————)—5 2 D ° 121 A summary of these data are presented in Table XIX. The specific interaction sites appear to be as follows, based on the values of AC : the 2-nitrogen for the l—MePz, max the 3—nitrogen for 1—MeIz, the 3—nitrogen for 1-Me—1,2,3-Trz, and the 4-nitrogen for 1—Me—1,2,4—Trz. However, in the case of 1,5-DiMeTz, the difference in the attachment of the two methyl groups to carbon and nitrogen on the ring and the distance from the interaction site to the probing nucleus leaves some doubt about the proper assignment. Most prob- ably the proper assignment is one of two alternatives; the silver ion either is coordinated to the 3—nitrogen or it is coordinated with equal probability to the 2—, 3—, and 4—nitro— gens respectively. One of the aims of this study was to determine the formation constants for the complexation reactions between the azole ligands and the silver(I) perchlorate in nitro— methane solutions. The proton magnetic resonance measure- ments have indicated that the exchange of the donor environ— ment between free and complexed states is very rapid, thus only one absorption per proton environment was observed. This study has also shown that the predominant component in Solution at Lig/Ag+ mole ratios > 2.00 is the 1:2 complex (ADZ) for the ligands 1—MeIz, l-MePz, and 1,5—DiMeTz. An attempt was made to determine the fOrmation constant Of the complex [Ag(1,5—DiMeTz)2]ClO4 in nitromethane solu— tion. It was assumed that the concentration of the 1:1 complex was negligible. Thus the relative fractions of the 122 00.0 I! 00.0 I- 0H.0 a NME 0 00.0 II 0H.0 I: 00.0 . 0 XMEU 00.0 I- HH.0 n- 00.0 0 00.0 I- 00.0 .I 00.0 00 000u0.0.Humer XMEU 00.0 1: I- I: 00.0 q NEE O 00.0 .. nu I: 00.0 . 0 XMEU 00.0 I- I- I: 00.0 0 Q 00.0 I- In I- 00.0 0 NamzH010.H 0mo no mum muv mum mu0 0m0uH .Aamm CH 0V Empmmm mpMHoHnunmm H0>Hflmlpcmmfla CH mocmmfla 0H0Nm so mucma 008030 U0>Hmmno mo cOmHHmmEOU .NHN manme Icoufl>c0 couonm psmam>flsvm mo mumanm Hm 123 VH.O Hw.h mw.h ov.b om.o vH.h hm.b Hm.® wN.o vm.o om.® mm.® mH.© mm.o mN.h mm.h mm.® wv.o mo.w wo.w H®.h mm.o Nh.v wb.h hm.h om.o vw.h om.h hm.h 0N.o bo.v OH.V Nw.m ®H.O ww.m mw.m ®®.m ®H.o bN.v ®N.vA mo.v NHBIm.N.Huwer 124 complexed and uncomplexed tetrazole were calculated from the chemical shift data (Table 111) and the estimated limiting chemical shift values of 20 and 17 Hz for the 5— methyl and l—methyl protons respectively. The resulting values for the overall formation constant were scattered over at least one order of magnitude (Table XX). It seems, therefore, that the 1:1 complex does indeed play an important role in the complexation reaction. It appears that the methods outlined for the formation constant determination are limited to that reported by Foreman, et al. (91) (page 35). However, the expression derived by them holds for the case where A, the acceptor (benzene) possesses the nucleus being measured and is com— Plexed to the donor (silver ions) forming the complexed SPecies ADZ. However, if the donor possesses the nucleus being measured, as in our case, a new expression must be derived as follows: A+D=AD AD+D=AD2(31) [AD ] K = __JEEZL_ K2 : .....i:.. (32) 1 [A] [D] [AD] [D] 2 [AD] = K1[A] [D] [AD2] =K1K2 [A] [D] (33) 34 Aobs = x1:1 A1 + x1:2 A2 ( ) thus: F 125 Table XX. Overall formation constant determination for the 1:2 complex based on relative fractions of free and complexed ligand. A [D0] Aobs ———-A°bs [AD2] [A] [D] Kf AD2 Based on 1—CH3 where AADZ = 17 Hz 0.259 14.8 0.871 0.113 0.0168 0.033 6,176 0.286 15.5 0.950 0.119 0.0114 0.048 4,531 0.337 16.1 0.945 0.123 0.00689 0.091 2,156 0.389 16.4 0.965 0.125 0.00455 0.139 1,422 0.441 16.2 0.953 0.124 0.00611 0.193 545 0.519 16.8 0.988 0.128 0.00156 0.263 1,186 Based on 5—CH3 where A = 20 Hz AD2 0.259 19.0 0.950 0.124 0.00650 0.011 157,660 0.286 19.0 0.950 0.124 0.00650 0.038 13,211 0.337 18.9 0.945 0.123 0.00715 0.091 2,077 0.389 19.4 0.970 0.126 0.00483 0.137 1,390 0.441 19.3 0.965 0.125 0.00455 0.191 753 0.519 19.5 0.975 0.127 0.00325 0.265 556 0.623 19.4 0.970 0.126 0.00390 0.371 235 0.778 19.4 0.970 0.126 0.00390 0.526 117 1_Aobs [A] = A0 ( A ) [D] = D0 — 2 [AD2] AD2 b [ADzl = A0 {—A0 S) AD2 [ADz] K : f [A] [D 2 126 [AD] K1 [A] [D] (35) x = = ———-—-——— 1:1 IDO] [Do] . 2[AD2] 2 K1 K2 [A] [D]2 X = ______ = —————-——+———-—— 36 1:2 [Do] [Do] ( ) combining equations 34, 35, and 36: K1 [A] [D] A1 + 2 K1 K2 [A] [D]2 A2 Aobs = D0 (37) Since [A0] >>> [Do]: [A] = [A01 (38) and [D] = [Do] - [AD] - 2[AD2] = [Do] — K1[A] [D] — 2K1K2 [A] [D]2 (39) Substituting equation 38 into equation 37: K1 [A0][D] A1 + 2K1K2 [A0][D]2 A2 obs = (40) [D0] Even if one substitutes equation 39 into equation 40 one does not eliminate the value for the equilibrium concentration of the free donor, [D], which we have no way of measuring in our systems. Thus the application of Foreman, Gorton, and Fosters' approach to the determination of the formation constant values for the 1:2 and 1:1 complexes in solution by nmr seems impossible. It is interesting to note, that when the acceptor nucleus is being measured the workable method is obtained, but when the donor molecule is being measured the method is no longer applicable. 127 Equation 40 may help to explain the shapes of the curves in Figures 5—14. Assuming that 99% of the donor is in the com— plexed form and only 1% is free in solution, then [D] = 0.01 [D0]. Under these conditions four factors govern the value of A0 they are A1, AZ, K1, and K2. In systems bs’ where the plots of Aobs XE Lig/Ag+ (or Ag+/Lig) mole ratios give smooth curves with no maxima, it appears that A2 > A1 and K2 > K1. However, in the cases where the plots pass through a maximum value, there are two possibilities; either A2 < A1 and K2 > K1 or A2 > A1 and K2 < K1. The first case assumes that the azole ligands coordinate with silver ions to form stepwiSe complexes similar to those exhibited for other nitrogen bases where K2 > K1 (Table xXI). If this condition holds then the terms A1 and A2 must influence the observed relative chemical shift and cause the maximum to occur. This maximum can only occur if A1 > A2. The second case assumes that A2 > A1 and indicates that K2 < K1. This is not the usual ordering of K1 and K2 in complex formation but it must not be overlooked as a possible ex- planation. The formation constants for these systems have not been measured by any other method, except for the 1—MeIz - Ag+ system in water (51). In order to check the importance of the 1:1 complex in the 1,5—DiMeTz - AgClO4 system in nitromethane solutions one additional experimental parameter was studied. In these studies the Lig/Ag+ mole ratio was held constant while the Concentration of the reactants was varied. Three systems 128 Table XXI. Literature values for the formation constants for silver(I) ligand interactions in aqueous solu— tions.\ Ligand Method Timp Conditions log 109 Ref. Used C K1 K2 Ammonia g1 25 -> O NH4N03 3.315 3.915 sol 25 O—corr 3.37 3.84 Ag 25 1 KNO3 3.31 3.91 Methyl amine 91 25 0.5 CH3NH3N03 3.15 3.54 Ethyl amine g1 25 0.5 KN03 3.37 3.93 Diethyl amine gl 25 50 mole% C2H5OH 3.26 3.17 gl 30 0.5 KN03 2.98 3.22 Triethylamine g1 25 0.4 C6H15NHN03 2.6 2.1 g1 25 50 mole% C2H5OH 2.31 1.79 nfButylamine gl 25 0.5 C4H11NHN03 3.43 4.05 7rw m mFJW u.(n 000m 0*o H\(D a Had a m m (L otrm i—Butylamine gl 25 0.5 KN03 3.38 3.86 E—Butylamine g1 25 50 mole% C2H5OH 4.01 4.25 E32522: 2s .... . gl 20 0.1 NaNO3 4.70 3.00 Ethanol amine gl 25 50 mole% C2H5OH 3.41 3.99 g1 30 ———> 0 3.07 3.57 gl 25 0.5 KN03 3.13 3.55 Benzylamine g1 25 0.5 KNO3 3.29 3.85 Imidazole gl 25 0.058 KCl 3.78 3.26 Pyridine gl 25 > 0 1.97 2.38 sol 25 -——+ 0 2.00 2.11 g1 25 0.5 KN03 2.04 2.18 d—Picoline gl 25 0.5 KN03 2.27 2.41 B—Picoline g1 25 ———> 0 2.00 2.35 Y-Picoline g1 25 ———> 0 2.03 2.36 2,4-Dimethyl— Piperdine gl 25 0.5 KNO3 3.16 3.45 d g1 25 0.5 KNO3 3.03 3.45 e Aniline g1 25 50 mole% C2H50H 1.38 1.50 f 2.6—Xylidine g1 25 50 mole% C2H50H 1.47 1.33 f QUinoline g1 25 50 mole% C2H50H 1.79 1.95 f 1,10—Phen— Ag 25 0.1 NaNO3 5.02 7.05 m anthroline Continued 129 Table XXI. Continued. gl sol Ag _>.0 O—corr glass electrode solubility measurements potentiometrically using silver electrode to follow free silver ions. value obtained by extrapolation to infinite dilution corrected to infinite dilution. J. Bjerrum, ”Metal ammine formation in aqueous solu— tion,“ Thesis, 1941, reprinted 1957, Copenhagen: P. H. Haase and Son. W. C. Vosburgh and R. S. McClure, J. Am. Chem. Soc., 65” 1060 (1943). R. Nasanen, Acta Chem. Scand., 11 763 (1947). J. Bjerrum, Chem. Rev., 46” 381 (1950). R. J. Bruehlman and F. H. Verhoek, J. Am. Chem. Soc., 22.! 1401 (1948). C. T. AnderSon, Doctoral Dissertation, Ohio State University, 1955. G. A. Carson, J. P. McReynolds, and F. H. Verhoek, J. Am. Chem. Soc., 61, 1334 (1945). G. Schwarzenbach, et al., Helv. Chim. Acta, E2} 2337 (1952). J. R. Lotz, B. P. Block and W. C. Fernelius, J. Phys. Chem., 62, 541 (1959). I. C. Smith, Doctoral Dissertation, Kansas State University, 1961. R. K. Murman and F. Basolo, J. Am. Chem. Soc., 71/ 3484 (1955). W. C. Vosburgh and S. A. Cosswell, J. Am. Chem. Soc., 62” 2412 (1943). J. M. Dale and C. V. Banks, Inorg. Chem., 2, 591 (1963). 130 were studied where the Lig/Ag+ mole ratios were held constant at 0.076, 1.02, and 1.53 (Table XXII). It appears from this study that the magnitude of the chemical shifts were de- pendent on the total concentration of the reactants as well as the Lig/Ag+ mole ratio. The shapes of these curves Aobs vs [Lig] are compared in Figures 15 and 16. Proton Nuclear Magnetic Studies in Acetonitrile Proton nmr studies for the complexation of azole deri— vatives with silver(I) perchlorate were also studied in a competitive solvent, acetonitrile. Acetonitrile has a Gutmann‘s donor number of 14.1 as compared to 2.3 for nitro- methane. The chemical shift assignments for the various proton environments of the free ligands in acetonitrile were made based on the literature values listed in Table II for other Solvents. These assignments are summarized in Table XXIII. The observed chemical shifts for the protons on the ligand molecules were measured on a series of solutions where the silver(I) perchlorate concentration was held constant at about 0.250 M and the concentration of the ligand was varied from about 0.01 to 1.25 M_(corre5ponding to ligand to silver ion mole ratios from 0.04 to 5.00),(Tables XXIV - XXVIII). These values were used to calculate the observed relative which were plotted as a function of chemical shifts (Aobs>' h .te the Lig/Ag+ mole ratios (Figures 17-21). In most cases - ver the Curves obtained went through a maleum value, howe I 131 Table XXII. Proton magnetic resonance study of the role of complex dissociation at constant 1,5-dimethyl- tetrazole to silver perchlorate mole ratios. (0) 1,5-DiMeTz/Ag+ = 0.765 0.0502 0.1005 0.1507 0.2009 0.2512 0.3014 0.4018 0.5023 1,5—DiMeTz/Ag+ 0.0249 0.0499 0.0898 0.1497 0.2495 0.3494 0.4492 1,5-DiMeTz/Ag+ 0.0502 0.1005 0.1507 0.2009 0.2512 0.3014 0.5100 [1,5-DiMeTz] (14) .0384 .0768 .1153 .1537 .1921 .2306 .3074 .3843 [I OOOOOOOO H O [0 0000000 H U1 [\3 H = 1.53 0.0768 0.1537 0.2306 0.3074 0.3843 0.4611 0.6123 5-CH 0(Hz) A(Hz) 163.7 13.6 164.5 14.4 166.8 16.1 166.1 16.0 167.2 17.1 167.6 17.5 167.8 17.7 168.0 17.9 161.6 11.5 162.4 12.3 163.6 13.5 165.1 15.1 166.2 16.1 166.5 15-4 166.6 16.5 164.5 14.4 164.5 14.4 165.0 14.9 166.5 16-5 PPt ‘— PPt 7’ 1-CH 0(Hz) Ain) 247.0 8.4 247.1 8.5 249.5 10.9 250.4 11.8 251.0 12.4 251.8 13.2 252.4 13.8 252.4 13.8 245.6 7 246.5 7. 247.6 9 249.2 10.6 250.6 12.0 under solvent under solvent 247.0 8 247.2 8 248.4 9 250.8 12 ppt ‘- ppt ‘— ppt '- Figure 15. A comparison of the curve shapes obtained when Um observed relative chemical shifts of the protons of 1,5—dimethyltetrazole were plotted versus U09] at constant Lig/Ag+ mole ratio of 1.02, 0.76, and 1.53 1—methyl protons 0 mole ratio 0.76 0 mole ratio 1.02 I mole ratio 1.53 Figure 16' A compariSOn of the curve shapes obtained when Um observed relative chemical shifts of the protons Of 1,5—dimethyltetrazole were plotted versus [L19] itsgonstant Lig/Ag+ mole ratio of 1.02, 0.76, and 5—methyl protons 0 mole ratio 0.76 0 mole ratio 1.02 I mole ratio 1.53 (Hz) obs (l5) 0 1 l 0.2 0.3 0.4 ( Li 9) M Figures 15 and 16. l 0.5 0.6 .. HAM—.4.“ 1M1" . i 134 0H0 H00 .1 00. 0 00021 00.0 00.0 i 00.0 00.0 0$21 00.0 0H.0 I: I- 00.0 00700.70sz 0H0 In 00.0 I 00.0 000110.702; 3.0 I- l I . 00.0 0000:0me 0mo Ho min mum mum mum 0mUIH UCSOQEOU 0 0 0 0 0 Afimmv .0HHHDHQODmom CH mosmmfla maonm 0:0 so mcououm 0C0Hm>flswm 0gp How mucchmHmmm uanm HmoHsmsu . HHHvOA QHQME 5 3 1 .muC080H5000E CH @005 003 UHSWHH DCMDmcH0QSm haso .wosoao wausmHHm 0E000Q mCOHDSHom* usmumcoo s H00.0 u HeoHoaan .1 0.000 I- 0.00H 0ammHH 0000 I- 0.H 0.000 0.H 0.00H 00.0 000.H* 0.H 0.000 0.H 0.00H 0H.0 000.H* 0.0 0.000 0.0 H.H0H 00.0 000.0. 0.0 0.000 0.0 0.H0H 00.0 000.0* 0.0 0.000 H.0 0.H0H 00.H 000.0* 0.0 H.000 0.0 0.H0H 00.H 000.0* 0.0 H.000 0.0 0.H0H 0H.H 000.0* 0.0 0.000 0.0 0.H0H 00.0 000.0* 0.0 0.000 0.0 0.H0H 00.0 00H.0* 0.0 0.000 0.0 0.H0H 00.0 0H00.0* 0.0 0.000 0.0 0.H0H 0H.0 0000.0 0.0 0.000 0.0 0.HOH 00.0 0H00.0 0.0 0.000 0.0 0.HOH 00.0 00H0.0 Nm 4 EUIm NE 0 NE Q mUIH NE 0 +m<\mflq mBmzmwwm.H .mafluuflcoumom CH Emumhm 000M0HL0H0Q H0>HHm paw 0HONwHumuahsumfiflolm.H 0:0 wo hosum 00smc000H OHumcmmE cououm .>Hu0n QHQMB 136 .mDC0E0HDmm0E CH 0005 003 005000 usauwcn0m50 waco .wodoao wausmflam 0E000Q mGOHDDHom* 0 000.0 Demamqoofi0oH000i 0.0 0.000 0.0 0.000 0.00 0.000 00.0 000.H* 0.0 0.000 0.0 0.000 0.H0 0.H00 H0.0 000.0. 0.HH 0.000 0.0 H.000 0.0H 0.000 00.0 000.0* 0.0H 0.000 H.0 0.000 H.HH 0.H00 0H.0 000.0. 0.0H 0.000 0.0 0.000 0.0 0.000 00.H 000.0* H.0H 0.000 0.0 0.000 0.0 0.000 00.H 000.0* 0.0H 0.000 H.0 0.000 0.0 0.000 00.H 000.0* 0.0H 0.000 0.0 0.000 0.0 0.000 00.0 00H.0 0.0H 0.000 H.0 0.000 0.0 H.000 00.0 H0H.0 0.0H 0.000 0.0 0.000 H.0 0.000 00.0 0000.0 0.0H 0.000 H.0 0.000 H.H 0.H00 0H.0 0000.0 0.0H 0.000 0.0 0.000 0.0 0.H00 00.0 0H00.0 .. I- I- I- I- 0.000 00.0 00H0.0 I- 0.000 I: 0.H00 I: 0.000 wemmHH 0000 Na 0 N0 0 Rea 180... E00 1500 9003 . 1.00 0:0 0:0 amolH + 000.0 0 Humer H0>HHm 0:0 0HONMHHDI0.N.HIH>SU0EIH 0:0 mo hosum 00chOm0H 0000QmmE cououm .0HHHDHGOM000 CH E00000 0umuoH£0H0m .>xx 0Hnms pcmumcoo .a 30.0 n 2.9.09: ®.h H.mhw m.MH m.mom H.v m.®mm wH.m m®N.H 0.0 0.000 0.0H 0.000 0.0 0.000 00.0 000.0 N.» N.®hv N.VH w.mom H.¢ m.®mm ow.m th.o O.h m.w>¢ o.vH ®.mom N.¢ ¢.®mm HH.m mmh.o H.0 0.000 0.0H 0.000 0.0 0.000 00.0 000.0 H.0 0.000 0.0H 0.000 0.0 0.000 00.H 000.0 H.0 0.000 0.00 0.000 0.0 0.000 00.H 000.0 V.® m.hbv h.NH m.vom O.¢ N.®mm ¢O.H mmN.o m.m w.©bv N.NH w.mom b.m m.mmm m®.o m®H.o m.v v.mhw m.HH H.mom w.m 0.0mm mm.o m¢wo.o m.v w.©hv h.HH m.mom v.m ®.mmm wN.o mhwo.o I! II II II m.m H.®mm HN.O mono.o II. 0.Hhv II. ©.Hmv II N.NMN Ucmmfla mwum ©w®.H ANmV< Avao Awmv< Aumvo Nm 4 va0 m<\mflq 0 may mlv Elm mmUIH + NHBIm N HImErH .QHHHUflCOumom Gfl Empmhw wumuoanonmm H®>HHm Uzm GHONmHHuIm0N‘Hlfihnumfilfi mnu MO hwdum mOGMCOmmH Ufluwcmmfi cououm .H>XX OHQMB 138 pcmumcoo 2 000.0 M 100003 II m.mwv II m.®Hv I: H.mH¢ II o.®HN Ucwmfla wwum II 0.m m.mvw w.v H.Hmv N.o m.mfiv v.m 0.0HN ov.® oom.H m.® v.0mv w.m 0.Hmv m.o ®.mH¢ ®.m m.mHN H0.m 0mm.H m.m o.mmv 0.0 m.mmv m.H ®.®H¢ H.m H.HNN m¢.0 boa.H m.HH o.mmv m.w $.0N0 0.N w.hH¢ b.m 0.HNN ww.m Hmw.o w.mH «.mmv m.oH N.hmv m.m v.0N0 N.> N.mmm ©0.N mH®.o H.HN ®.0©¢ m.MH N.om¢ 0.0 o.mN¢ w.h w.mNN wv.H mom.o m.mH v.m®¢ h.MH o.omv H.b N.NNO ®.w $.0NN wH.H mmN.o m.wH 0.va N.MH m.mm0 N.w m.HN¢ m.w n.0NN ow.o HNN.O w.0H m.H®v ®.NH m.wm¢ m.m 0.0N0 m.w m.¢NN mm.o 00H.o m.pa w.ow0 m.NH w.wmv m.v ©.®H0 N.w N.¢NN mm.o wwmo.o m.mH o.am¢ w.HH H.wmw h.N w.hH¢ w.n w.mmm om.o mmvo.o I I I- I I- .i 0.0 0.000 00.0 0000.0 5 I, I: In. I: .i 0.0 0.000 00.0 0000.0 $.50 30: E00 $.50 350 $.50 E00 350 EEG EN 0-0 0-0 0.0 Infill + N32 0 .mafluuflcouwom CH Ewumhm m#muoaflo Inmm Hw>HHm Cam wHONwUHEflaxcumfilfi mag mo mUSum mocmcowmu OHumcmmE Couonm .HH>NN maQMB 139 pcmumcoo 04 000.0 n 0000003 0.0H N.mmv 0.0 m.mvv m.m n.0wm m.m H.0mm 00.0 wmoo.o $.0H v.mnw m.m m.omv ©.m w.owm w.m 0.0mm wo.o mmao.o $.0H w.mmv N.m 0.0mv m.m b.0wm w.m 0.0mm NH.o owwo.o m.wH h.mmv h.m m.omv b.m m.owm m.© n.0mm ®H.o mwmo.o w.vH ®.mmv h.m m.om¢ w.m w.owm N.© 0.0mm ON.o vao.o m.0H H.mmv w.m ®.omv m.m b.0wm m.© n.0mm om.o mmvo.o h.mH m.wmv o.® w.omv N.m v.0wm v.® 9.0mm 00.0 wmmo.o v.MH N.wmw o.m w.om0 ®.w w.m>m w.m 0.0mm H®.o mvH.o H.NH m.©mw w.¢ ®.mv¢ H.w m.mhm w.m 0.0mm Hw.o me.o ©.OH w.mmv b.m m.w¢v w.© w.hhm o.m N.mmm Ho.H H¢N.o ¢.m N.0mw m.m «.000 ®.m w.®hm ¢.m m.HmN 00.H >mm.o N.w o.mmv 0.H N.©wv m.v H.®hm ©.N w.omN Nw.H vmv.o m.b m.mnv 0.H w.mwv N.¢ «.m0m o.N N.omm NN.N 0mm.o II w.0ww II. w.vvw II N.Hbm II N.wmm Ucmmfla mwnw II 0m 4min 0m 0 0m 4000 Nm 0 0m HHm Ucm wHONmuhmahaqul .wafinuflqouwom CH Eoumhm mumuoHno H ms“ mo hwsum wocmcommu 00umcmmE Cououm .HHH>NN magma Figure 17. 140 a) Relationship between the observed relative chemical shift of the protons of 1,5—dimethyl- tetrazole and the Lig/Ag+ mole ratio in aceto- nitrile [AgClO4] was constant [Lig] was varied O l—methyl protons (left ordinate) O 5-methyl protons (right ordinate) b) Relationship between the observed relative Chemical shift of the protons of 1,5—dimethyl— tetrazole and the Ag+/Lig mole ratio in aceto- nitrile [Lig] was constant [AgClO4] was varied ° l-methyl protons (left ordinate) 0 5—methyl protons (right ordinate) (H2) Aobs 141 . + LIg/Ag MOLE RATIO Ag*/Lig MOLE RATIO Figure 17. O l 2 3 4 6 l l l l l *__7 (A) g 1 ' L l I o I 2 3 4 6 Figure 18. 142 Relationship between the observed relative chemi- cal shift of the protons of 1—methyl-1,2r4“trl‘ azole and the Lig/Ag+ mole ratio in acetonitrile [AgClO4] was constant [Lig] was varied o 1—methyl protons o 5—proton I 3—proton (Hz) AObs 1* 1 I I l 1 O I 2 3 4 5 s Lig/Ag‘ MOLE RATIO Figure 18. i- 144 Figure 19. Relationship between the observed relative Cheml- cal shift of the protons of 1—methyl-1.2,3jtr}' azole and the Lig/Ag+ mole ratio in acetonitrile [AgClO4] was constant [Lig] was varied o 1—methyl protons O 5—proton I 4—proton 145 l l l 2 3 4 Ag*/Lig MOLE RATI Figure 19. l 5 O _— w 146 Figure 20. Relationship between the observed relative chemi- cal shift of the protons of l—methylimidazole and the Lig/Ag+ mole ratio in acetonitrile [AgClO4] was constant [Lig] was varied o 1—methyl protons (left ordinate) o 5-proton (left ordinate) u 2—proton (right ordinate) I 4—proton (right ordinate) I’ ‘24 24 D ' D ‘20 20— -l6 A I .- 5; 6 ‘l2 V I U §I2 ‘ - 8 an q I [E 8" '4 4.. — 0 g 0- ‘1 T l_ J J I l I I : O I. 2 3 4 5 6 Lig/Ag MOLE RATIO Figure 20. @ Liiwi a; a 148 Figure 21. Relationship between the observed relative chemi- cal shift of the protons of l-methylpyrazole and the Lig/Ag+ mole ratio in acetonitrile [AgClO4] was constant [Lig] was varied O l-methyl protons (left ordinate) O 5-proton (left ordinate) u 3-proton (right ordinate) I 4-proton (right ordinate) 149 I— J l J l O | + 2 Lig/Ag MOLE RATIO Figure 21. 150 1-methyl and the 5—methyl protons of the 1,5—DiMeTz (Figure 17a), the l-methyl protons of 1-Me—1,2,4—Trz (Figure 18), and the 1—methyl protons of 1-Me—1,2,3—Trz (Figure 19) gave smooth curves with no maxima. In addition to the reasons outlined for the systems in nitromethane whose curves went through maximum values, the solvent acetonitrile has a greater influence upon the complexation equilibrium. The ligand molecules are not only involved in the simple AD and AD2 complexes but are also involved in mixed solvent— ligand complexes (or intermediate solvated Species) such as sn A D2_n. An additional experiment was performed in acetonitrile to compare the complexing ability of 1,5-DiMeTz with the bi- tetrazole, 1,4—bis(1-methyl—5-tetrazolyl)n—butane recently studied by Septemia Policec (118) in this laboratory. In both cases, the ligand concentration was varied, such that the Lig/Ag+ mole ratios varied from 0.10 to i 10. The chem— ical shifts of the 1—methyl protons of 1,5—DiMeTz increased from 3.92 to 4.01 ppm while the value for the 5-methyl pro— tons increased from 2.47 to 2.56 ppm (Table XXIX). The limiting relative chemical shift for the l—methyl protons of the bitetrazole was about 6 Hz (0.10 ppm) while that for the 1,5-DiMeTz was about 4 Hz. When the relative chemical shifts observed were plotted as a function of the Ag+/Lig mole ratios, smooth curves were obtained (Figure 17b). 151 N.N 0.0mH H.N n.0mm wH.H voafl.o mmmo.o H.N m.omH H.N n.0mm mo.H vooH.o memo.o m.H H.0mH o.N 0.0mm ow.o momo.o wHOH.o 0.H m.m¢a w.H N.bmm hw.o mowo.o mmmo.o 0.H m.m¢H m.H m.>mm mh.o mono.o mwwo.o m.H >.mva ®.H 0.0mm 00.0 Nomo.o mmwo.o ¢.H ®.®¢H 0.H O.hmm mm.o Nomo.o homo.o w.o O.m¢H m.o m.®mm ww.o Nowc.o Nfimo.o 0.0 m.w¢H H.H m.®mm mm.o Homo.o wmmo.o H.0 m.w¢H v.0 w.mmm NN.O OON0.0 WNm0.0 II N.wvH H.0 m.mmm HH.O 00H0.0 NNm0.0 II N.wvH II w.mmm onmmfla mmnm II ommo.o AnmvammOI0A 00: 0 A05 00090 A 05 0 03?? 00a? Emma .OHHHUHGOOOOO n0 Emu mo mosum mocchmm UGO OHONmuumuawgumEflUIm.H map mam mumHOHnonmm Hm>aflm H UHpOGmmE GOpOHm .XHNN OHQMB 152 ucmumcoo 2 000.0 M 0000200I0.00 0.0 0.000 0.0 0.000 00.0 0000.0 0000.0 0.0 0.000 0.0 0.000 00.0 0000.0 0000.0 0.0 0.000 0.0 0.000 00.0 0000.0 0000.0 0.0 0.000 0.0 0.000 00.0 0000.0 0000.0 0.0 0.000 0.0 0.000 00.0 0000.0 0000.0 0.0 0.000 0.0 0.000 00.0 0000.0 0000.0 0.0 0.000 0.0 0.000 00.0 0000.0 0000.0 0.0 0.000 0.0 0.000 00.0 0000.0 0000.0 0.0 0.000 0.0 0.000 00.0 0000.0 0000.0 0.0 0.000 0.0 0.000 00.0 0000.0 0000.0 0.0 0.000 0.0 0.000 00.0 0000.0 0000.0 0.0 0.000 0.0 0.000 00.0 0000.0 0000.0 153 Sodium—23 Magnetic Resonance Studies To determine the relative donor abilities of the azoles, a mixed solvent study (page 42) was performed in nitrometh— ane, acetonitrile, and acetone solutions. However, in all cases the sodium ion resonance line width at half peak height became so broad that at mole fractions (Ligand/ Ligand + solvent) > 0.10 the data could not be collected using the Varian DA60 spectrometer in wideline configuration Thus only solutions Lig/Lig + solvent mole fraction < 0.10 were studied in order to note trends in the sodium ion elec- tron density changes. Since the amount of solvent was nearly constant, the chemical shift of the sodium—23 reso— nance was observed as a function of the mole ratios Lig/Na+ (Tables XXX—XXXIV). Figures 22, 23, and 24 repre— sent the five ligands in nitromethane, acetonitrile, and acetone respectively. If the donor ability of the azole ligands is greater than the solvent, one would expect a rapid decrease in the sodium-23 chemical shift. In the least donating solvent nitromethane (D.N. = 2.3), this type of trend is noted. All five ligands show a decrease in the chemical shift with in— creasing Lig/Na+ mole ratio. When acetonitrile (D.N. : 14.1) is used as the reaction medium, the donating abilities of the azole ligands begin to differentiate (Figure 23). When a solvent with donor number 17.0 (acetone) was chosen, the ligands are clearly differentiated and 1~MeIz appears to have the greatest donating ability with Table XXX. 154 Sodium—23 nuclear magnetic resonance study of 1,5-dimethyltetrazole and sodium tetraphenyl— borate in nitromethane, acetonitrile, and acetone. . O [1,5-DiMeTz] [NaB(C6H5 )4] Lig/Na+ Na—23 L.W. (0) (L4) (Hz) (ppm) (Hz) in nitromethane K —— 0.250 ~— 247 15.6 26 0.0776 0.255 0.30 238 15.0 37 0.155 0.253 0.61 221 13.9 42 0.233 0.258 0.90 215 13.5 46 0.388 0.257 1.51 194 12.9 55 0.776 0.252 3.08 175 11.0 70 1.164 0.256 4.55 144 9.1 83 in acetonitrile —— 0.250 —— 131 8.25 18 0.0693 0.241 0.29 131 8.25 30 0.139 0.245 0.57 133 8.38 38 0.208 0.240 0.87 133 8.38 35 0.346 0.245 1.41 135 8.50 35 0.693 0.241 2.88 121 7.62 38 1.039 0.244 4.26 117 7.37 35 in acetone -- 0.250 -— 164 10.3 17 0.0736 0.258 0.29 146 9.19 29 0.147 0.247 0.60 148 9.32 27 0.221 0.262 0.84 141 8.88 30 0.368 0.254 1.45 147 9.26 26 0.736 0.260 2.83 142 8.94 27 1.104 0.257 4.30 140 8.82 26 155 Table XXXI. Sodium—23 nuclear magnetic resonance study of 1—methyl—1,2,4-triazole and sodium tetraphenyl— borate in nitromethane, acetonitrile, acetone, and pyridine. [1—Me—1,2,4-Trz] [NaB)C6H5)4] Lig/Na+ 5Na—23 L.W. (11) (DA) (HZ) (ppm) (HZ) in nitromethane ‘ -- 0.247 -— 245 15.4 28 0.0726 0.241 0.30 219 13.8 52 0.145 0.243 0.60 202 12.7 63 0.218 0.244 0.89 179 11.3 74 0.363 0.243 1.49 153 9.63 109 0.726 0.249 2.92 103 6.49 very broad 1.089 0.250 4.36 74 4.66 very broad in acetonitrile -- 0.250 —- 130 8.19 18 0.0912 0.243 0.38 127 8.00 26 ‘ 0.182 0.243 0.75 123 7.75 33 0.274 0.241 1.14 113 7.12 31 0.456 0.243 1.88 101 6.36 36 i 0.912 0.242 3.77 74 4.66 38 1.368 0.241 5.65 55 3.46 43 1 in acetone __ 0.250 —— 162 10.2 19 ‘ 0.0904 0.246 0.37 , 143 9.01 37 I 0.181 0.242 0.75 131 8.25 37 1 0.271 0.242 1.12 127 8.00 37 1 0.452 0.242 1.87 117 7.37 37 0.904 0.243 3.72 91 5.73 41 1.356 0.239 5.67 76 4.79 47 in pyridine -- 0.246 -- —3 -O.19 30 0.0990 0.236 0.42 —4 —0.25 33 ) 0.198 0.236 0.84 -6 —0.35 35 0.297 0.236 1.26 —6 -0.38 35 0.495 0.236 2.10 —7 —0.44 36 0.989 0.236 4.19 —16 «1.01 38 1.485 0.234 6.35 —21 -1.32 41 Table XXXII. Sodium-23 nuclear magnetic resonance study of 1—methyl—1,2,3-triazole and sodium tetraphenyl— borate in nitromethane, acetonitrile, and acetone. [1-Me—1,2,3—Trz] [NaB(C6H5 )4] Lig/Na+ éNa—23 L.W. ‘1 <4) 01) (Hz) (ppm) (Hz) J in nitromethane -— 0.250 —— 247 15.6 27 0.0868 0.240 0.36 236 14.7 38 0.174 0.241 0.72 221 13.9 39 0.347 0.242 1.43 190 12.0 51 0.521 0.240 2.17 172 10.8 79 0.868 0.241 3.60 133 8.38 99 1.302 0.239 5.45 -- —- very broad a in acetonitrile -- 0.250 —— 130 8.19 18 7 0.0923 0.250 0.37 130 8.19 27 { 0.184 0.242 0.76 128 8.06 31 0.369 0.241 1.53 123 7.75 31 1 0.554 0.238 2.33 116 7.30 32 1 0.923 0.240 3.85 110 6.93 31 1.384 0.239 5.79 101 6.36 31 in acetone -- 0.250 —— 163 10.3 18 0.0875 0.240 0.36 146 9.19 36 0.175 0.242 0.72 143 9.01 35 0.350 0.238 1.47 146 9.19 29 0.525 0.247 0.213 135 8.50 27 0.875 0.242 3.62 129 8.12 31 1.313 0.233 5.64 128 8.06 32 157 Table XXXIIL Sodium—23 nuclear magnetic resonance study of lfmethylimidazole and sodium perchlorate in nitromethane, acetonitrile, acetone and pyridine. [1 MeIz] [NaB(C6H5 )4] Lig/Na+ 5Na_23 L.W. 1 (D1) (D1) (Hz ) (ppm) (HZ) in nitromethane —- 0.250 —— 247 15.6 28 0.0272 0.252 0.11 216 13.6 46 0.0950 0.256 0.37 178 11.2 63 0.149 0.256 0.58 173 10.9 69 0.336 0.258 1.30 144 9.07 72 0.506 0.256 1.98 138 8.69 86 0.674 0.254 2.65 115 7.24 119 1.010 0.258 3.91 86 5.42 144 in acetonitrile -- 0.500 —— 132 8.31 31 0.0800 0.496 0.16 134 8.44 34 0.198 0.506 0.39 123 7.75 37 0.274 0.500 0.55 114 7.18 39 0.352 0.508 0.70 109 6.86 43 0.524 0.508 1.03 100 6.30 46 0.720 0.504 1.43 89 5.60 51 0.984 0.508 1.93 77 4.85 63 1.180 0.490 2.41 72 4.53 ‘ in acetone —- 0.500 -- 163 10.3 43 0.0694 0.498 0.14 149 9.38 43 0.278 0.502 0.57 134 8.44 46 0.556 0.502 1.11 103 6.49 49 ‘ 0.832 0,508 1.63 89 5.60 58 1.25 0.496 2.52 72 4.53 63 1.64 0.506 3.24 49 3.09 75 1.96 0.504 3.90 34 2.14 81 2.50 0.508 4.52 26 1.64 81 in pyridine -- 0.500 -~ ~3.0 -0.19 30 0.214 0.514 0.42 —3.0 -0.19 88 0.428 0.516 0.83 ~7.0 -O.44 9 I o -18 -1.13 95 0 854 0.538 1.53 ' —29 —1 .83 97 1 28 0.498 2.57 . _43 -2.71 100 1.71 0.520 3 .29 158 Table XXXDL Sodium—23 nuclear magnetic resonance study of l-methylpyrazole and sodium tetraphenylborate in nitromethane, acetonitrile, and acetone. [l-MePz] [NaB(C6H5 )4] Lig/Na+ 5Na_23 L.W. (L4) ' (£4) (HZ) (ppm) (H2) in nitromethane -- 0.250 -- 247 15.6 28 0.0769 0.261 0.29 240 15.1 33 0.154 0.261 0.59 226 14.2 39 0.231 0.260 0.89 212 13.4 45 0.384 0.261 1.47 191 12.0 53 0.769 0.260 2.96 159 10.0 59 1.153 0.260 4.44 120 7.56 >86 in acetonitrile -- 0.250 —- 131 8.25 20 0.0781 0.259 0.30 101 6.36 28 0.156 0.263 0.59 76 4.79 30 0.234 0.263 0.89 62 3.90 33 0.391 0.260 1.50 63 3.97 34 0.781 0.263 2.97 60 3.78 35 1.172 0.259 4.52 54 3.40 38 in acetone -- 0.250 —— 163 10.3 19 0.0793 0.256 0.31 134 8.44 29 0.159 0.244 0.65 139 8.75 30 0.238 0.257 0.93 139 8.75 28 0.397 0.256 1.55 135 8.50 32 0.793 0.255 3.11 123 7.75 34 1.190 0.257 4.63 116 7.30 34 159 Figure 22. Relationship between the observed chemicalsflfiit of the sodium—23 ion and the Lig/Na+ mole ratMJ for the azole ligands in nitromethane. 1,5—DiMeTz 1-Me—1,2,3-Trz leMe-1,2,4-Trz l-MeIz <>D<1l>o l-MePz Am HM CHEMICAL SHIFT (ppm) N0-23 or 1 l 1 ‘ 2 3 4 5 Lia/Na“ M OLE RATIO Figure 22. 161 Figure 23. Relationship between the observed chemical shift of the sodium-23 ion and the Lig/Na+ mole ratio 1 for the azole ligands in acetonitrile. i' 1,5-DiMeTz 1—Me—1,2,3—Trz 1-Me—1,2,4—Trz 1—MeIz <>EJO l—MePz 162 .- o A v = Q A. I V E 0‘. V S A. E a: v d O a i Q .5...» O -3\ .1 n _ _ u p Q. nlu 8 6 4 5 4 MOLE RATIO 3 + a 2 Lig /N Figure 23. u—— ......v‘ Figure 24. 163 Relationship between the observed chemical Shjrift of the sodium—23 ion and the Lig/Na+ mole ratna for the azole ligands in acetone. 1,5-DiMeTz 1—Me-1,2,3-Trz 1-Me-1,2,4-Trz l-MeIz l-MePz ODdDo 164 I4-F A _ 9. F. AU 00 no aathiIm 4<0_EMIO MN-oz 35 m _ 4 o” MOLE RATIO Lig/N Figure 24. 165 1-Me-1,2,4-Trz > l-MePz > 1-Me-1,2,3-Trz > 1,5—DiMeTz (Fig- ure 24). Since leMe-1,2,4—Trz and 1—MeIz were similar in donor abilities in nitromethane and acetonitrile, a fourth solvent (pyridine) was also studied in order to substantiate the donor order observed in acetone. The results are shown in Figure 25 and do indicate that l-MeIz has better donor ability than 1—Me-1,2,4-Trz. In order to check on the relative donor strengths of these compounds four nearly saturated solutions of sodium tetraphenylborate in the pure ligands 1—Me—1,2,3—Trz ([Na+] = 0.250 L4): 1-Me—1,2,4-Trz ([Na+] = 0.125 g), l-MePz ([Na+] = 0.250 M_) and 1—MeIz ([Na+] = 0.250 a) were measured on the NMR Specialities MP100 Fulsed Spectrometer. The ab— sorptions (referenced to saturated aqueous sodium chloride solution) were very broad ~ 200 Hz at half peak height. Therefore, only the positions of the sodium—23 resonance were recorded. The chemical shifts for 1-Me-1,2,3—Trz, 1— MePz, 1-Me-1,2,4-Trz, and l—MeIz were -1.23, -4.08, —4.32, and -11.02 ppm respectively. These chemical shift values correspond to donor numbers of 36, 41, 41.5, and 54 based on the data presented by Erlich and Popov (98) and Herlem and Popov (100) (Figure 26). From these data, it seems that the azoles are comparatively strong donors. Figure 25. 166 Relationship between the observed chemical 52%gt of the sodium-23 ion and the Lig/Na+ mole re 1 for l—methylimidazole and l—methyl-ll2,4’tr1‘ azole in pyridine. E] l—MeIz ‘7 l-MePz (ppm) Na-23 CHEMICAL SHIFT 167 I 11 I 1 2 3 4 5 LIg/NJ MOLE RATIO Figure 25. .— Figure 26. 168 Relationship between the observed chemical shift of the sodium—23 ion in nonaqueous solvents and the donor number of the solvent. 1 nitromethane, 2 benzonitrile, 3 acetonitrile 4 acetone, 5 ethyl acetate, 6 tetrahydrofUIML 7 dimethylformamide, 8 dimethylsulfoxide, 9 Pyridine, 10 hexamethylphosphoramide, 11 hydrazine, 12 ethylenediamine, 13 ethylaInine 14 lSO-propylamine, 15 ammonia, 16 1rwmAw~Ongpmpcmpwewv-m.rvmwn we Eggpuwam vwxmgwcw Lam .w wgzmwg .Eo an F 03 F One 02. _ ,o ON 9. _‘ /o _ i. - I g. H 4 7 , Om , - 8 _ co. owH cu...u _¢;nu . 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