A STUDY OF SOME TRANSITION METAL COMPLEXES WITH PENTAMETHYLENETETRAZOLE Thom {*m‘ the Degree of M. S. . MICHRGAN sum URKVERSETY Frank Michael. D’Itri 1966 LIBRAR Y IHESIS Michigan State University ' «Vining 1“ ' .j‘x‘.‘ ’ , ABSTRACT A STUDY OF SOME TRANSITION METAL COMPLEXES WITH PENTAMETHYLENETETBAZOLE by Frank M. D'Itri Complex compounds of pentamethylenetetrazole (metrazole. hereafter abbreviated as PMT) have been prepared with manganese(II), iron(II), iron(III). cobalt(II), nickel(II), copper(II), and zinc(II) perchlorates by the following two techniques. 1. The hydrated metal perchlorates were dissolved in 2,2'- dimethoxypropane. The water of hydration was removed by the reaction with the solvent. The excess PMT was added and the respective complexes precipitated out as microcrystalline powders. 2. Hydrated copper(II) perchlorate was dissolved in anhydrous acetic acid, and a calculated amount of acetic anhy- dride was added to react with the water of hydration. Anhydrous salt Cu(0104)2°xHOAc precipitated out. The crystals were filtered, dissolved in hot HDAc and an excess of PMT was added. The Cu(PMT)4(Clo)2 complex precipitated out. The above techniques had to be used since it is virtually impossible to remove the water of hydration from transition metal perchlorates (except A3010“). The usual dehydration pro- cedures lead to decomposition (sometimes explosive!) of the Frank M. D'Itri salt. The data indicate that the complexes with iron(II) and iron(III) perchlorates contain 3-5% impurities and that, in all probability. they are a mixture of the respective iron(II) and iron(III) complexes. Using the same method of preparation, Cu(PMT)2ClOu and Cu(PMT)4(ClOu)2 complexes were also isolated. All of these complexes are quite stable below 1000 and, except for Cu(PMT)ZClou, they are soluble in water and polar non- aqueous solvents but insoluble in non-polar solvents. Karl Fischer titrations and elemental analyses indicate that the com- plexes are anhydrous. The reflectance spectra of all of the complexes were obtained. It is interesting to note that the Spectra of the cobalt(II) and nicke1(II) complexes corresponded to the respective ions in an octahedral configuration. On the other hand, the XLray powder diffraction measurements on these complexes indicate that all complexes containing six PMT molecules per metal ion are isomorphous. These data combined with the reflectance Spectra data seem to indicate that in the Cu(PMT)6(C104)2 complex, six PMT molecules are coordinated to the copper(II) ion. Six coordinate copper(II) is rather unusual since all attempts to prepare correSponding solid copper pyridine complexes (in this laboratory as well as in others) have been unsuccessful so far. _ Magnetic susceptibility studies on the hexakis(PMT)- transition metal perchlorate complexes were interpreted on the basis of octahedral coordination, and the complexes are of the high spin type. Frank M. D'Itri The electron spin resonance spectra of Mn(PMT)6(C104)2, Cu(PMT)6(C104)2 and Cu(PMT)4(ClOQ)2 were obtained. For Mn(PMT)6(0104)2 complex dispersed in Zn(PMT)6(0104)2 the data indicate that the metal-ligand bonds are highly ionic (91%) and that there is a large distortion from octahedral symmetry. The measurements on Cu(PMT)6(C104)2 show that the copper symmetry is tetragonal. Nuclear magnetic resonance studies of the complexes re- vealed that only the diamagnetic Zn(PMT)6(0104)2 and Cu(PMT)2ClOu yielded the predicted spectra. The remainder of ' the complexes, being paramagnetic complexes, yielded no spectra within the sweep width limits of the Varian A60 NMR Spectro- meter. It is believed that the absorbances were shifted be- yond the range of the instrument. Infrared spectra of these complexes diSpersed in Nujol were obtained in the 5000-670 cm‘1 region. The Spectra were essentially those of the ligand with very little perturbation. The infrared Spectra also indicated that the complexes are ionic Since there is only a large single broad band at approxi- 1 zmately 1080 cm' for the perchlorate ion. The far infrared naeasurements, however, Show two distinct types of spectra. Those cxf the hexakis and tetrakiS(PMT) transition metal complexes Show tnvo new bands located in the 277-288 cm‘1 and 236-198 cm"1 v——_:7——-""-’ . ”Fm.“ _...._._, Frank M. D'Itri regions. These bands have been very tentatively assigned to the asymmetric stretch of the metal-nitrogen bond and the metal-ligand bending mode, respectively. There is a trend for the bands in the 320-180 cm"1 region to increase in fre- quency with a decrease in ionic radius (increase in polarizing ability) of the central metal ion. The Spectrum of the bis(PMT)00pper(I) perchlorate, on the other hand. has a band at 281 cm"1 and what appear to be weak bands at 255 and 198 cm'l. The 281 and 255 cm“1 bands could be assigned to the PMT with no bands present for the metal-nitrogen asymmetric stretch or metal-ligand bending mode. An alternative assign- ment for the 281 cm"1 would be the metal-nitrogen asymmetric stretch while the 198 cm"1 band could correSpond to the metal- ligand bonding mode. A STUDY OF SOME TRANSITION METAL COMPLEXES WITH PENTAMETHYLENETETRAZOLE By Frank Michael D'Itri A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Chemistry 1966 ———-«.._ EPA ACKNOWLEDGEMENT The author wishes to express his Sincere appreciation to Professor Alexander I. POpov for his guidance, assistance,and encouragement during the course of this investigation. Special thanks goes to my wife, Patricia Ann, for her patience and understanding. Financial assistance from the Mental Health Institute of Public Health Service is grate- fully acknowledged. The author also wishes to express thanks to Professor Luigi Sacconi, University of Florence, Italy, for the reflectance Spectra and some of the X—ray diffraction patterns, Professor Alexander Tulinsky for assistance with the X-ray powder diffraction pattern interpre- tation, Dr. Henry A. Kuska for the electron Spin resonance and its interpretation, Joseph A. Caruso for the reproduction of most of the figures, the Dow Chemical Company for the thermo- gravimetric analysis and generous supplies of chemicals and Professor Carl H. Brubaker, Jr.. Joseph T. Lundquist and John H. Bloor for their many helpful discussions during the course of this investigation. ************ 11 I. II. TABLE OF CONTENTS HISTORICAL 0 O O O 0 O O O O O O O O O O 0 0 EXPERIMENTAL O O O O O O O O O 0 O O O 0 O 0 Reagents. . . . . . . Analytical Methods. . . . . . Instrumentation . . . . . . Experimental Procedures Selection of a Copper(II) Salt for the Spectrophotometric Study of the Donor Properties of PMT. . . .-. Solubility of Various Copper Salts in. Purified Nitromethane. . . . . Attempted Preparation of Anhydrous Copper(II) Perchlorate . . . . . . . . Preparation of Coordination Compounds of Pentamethylenetetrazole. . . Bis(pentamethylenetetrazole)cOpper(I) Perchlorate. . . . . . . . . . . . . Reaction in DMP. . . . . . . . . . . Reaction in Nitromethane . . . . . Tetrakis(pentamethylenetetrazole)- c0pper(II) Perchlorate . . . . . . . Reaction in DMP. . . Reaction in Anhydrous Acetic Acid. Reaction in Nitromethane . . . . . Hexakis(pentamethylenetetrazol.e)- 00pper(II) Perchlorate . . . . . Preparation of Hexakis(pentamethylene- tetrazole)copper(II) Perchlorate Crystals . . . . . . . . . . . . . . Hexakis(pentamethylenetetrazole)- nickel(II) Perchlorate . . . . . . . Hexakis(pentamethylenetetrazole)- manganese(II) Perchlorate. . . . . . . Hexakis(pentamethylenetetrazole)- cobalt(II) Perchlorate . . . . . . . Hexakis(pentamethylenetetrazole)- zinc(II) Perchlorate . . . . . . Hexakis(pentamethylenetetrazole)- iron(II) Perchlorate . . . . . . . Hexakis( entamethylenetetrazole)- iron(III Perchlorate. . . . . . . . . O O O O O O 0 O O O O O O O O O O O O O 111 O 0 O O Page 1L» in 15 18 19 29 30 34 36 36 36 37 w—m-wr. TABLE OF CONTENTS - Continued Page The Attempted Preparation of the Chromium(III) and Vanadyl Penta- methylenetetrazole Complexes. . . 37 Karl Fischer Analysis of the Transition Metal Complexes of Pentamethylene- tetrazole . . . . 38 SpectrOphotometric Studies of Copper(II) Complexes in Pentamethylenetetrazole. . . 38 Beer's Law Study. . . . . . . . . . . . 38 Mole Ratio and Continuous Variation Studies of Copper-PMT Complexes in Purified Nitromethane . . . 39 Spectrophotometric Study of the Copper(II) Perchlorate-Pentamethylenetetrazole System in Nitromethane. . . . . 39 COpper(II) Perchlorate-Hexahydrate. . . 39 The Hexakis(pentamethylenetetrazole)- c0pper(II) Perchlorate. . . . 43 The Tetrakis(pentamethylenetetrazole)- copper(II) Perchlorate. . . . 43 Attempted Determination of the Stepwise Formation Constants by Spectrophoto- metric Methods. . . . . . . “7 Visible and Reflectance Spectra of the Transition Metal Complexes of Penta- methylenetetrazole. . . . . . . “7 Visible and Near Infrared Spectra . . . 47 Cobalt(II) Perchlorate Hexahydrate and Hexakis(pentamethylenetetrazole)- cobalt(II) Perchlorate. . . . . 4? Nicke1(II) Perchlorate Hexahydrate and Hexakis(pentamethylenetetrazole)- nickel(II) Perchlorate. . . . . 49 COpper(II) Perchlorate Hexahydrate, Tetrakis and Hexakis(pentamethylene- tetrazole) copper(II) Perchlorate . . . 51 Reflectance Spectra . . . . . . . . 54 Thermogravimetric Studies of the Transi- tion Metal Complexes of Pentamethylene- tetrazole . . . . . 54 Tetrakis( entamethylenetetrazole)- cOpper(II Perchlorate. . . . . . . . . 54 iv TABLE OF CONTENTS n Continued Page Hexakis(pentamethylenetetrazole)- cepper(II) Perchlorate . . . . . . . . 58 Hexakis(pentamethylenetetrazole)- manganese(II) Perchlorate. . . 58 Magnetic Susceptibility of the TranSition Metal Complexes of Pentamethylene- tetrazole. . . . 60 Calculation of Magnetic Susceptibility of Hexakis(pentamethylenetetrazole)- copper(II) Perchlorate . . . . . . 63 X-ray Powder Diffraction Studies of the Transition Metal Complexes of Penta- methylenetetrazole . . . . . . . . 64 Hexakis(pentamethylenetetrazole)- transition Metal Perchlorates. . . . . . 68 Tetrakis( entamethylenetetrazole)- cOpper(II Perchlorate . . . 70 BiS(pentamethylenetetrazole)copper(I)o Perchlorate. . . . . . . . . . . . 70 Electron Spin Resonance Studies of the Transition Metal Complexes of Penta- methylenetetrazole . . . . . . . 79 Nuclear Magnetic Resonance Studies of the Transition Metal Complexes of Penta- methylenetetrazole . . . . . . . . . . . . 80 Pentamethylenetetrazole. . . . . . . 80 Hexakis(pentamethylenetetrazole)-o zinc(II) Perchlorate . . . 80 Bis(pentamethylenetetrazole)c0pper(I)° Perchlorate. . . .3 80 Tetrakis and Hexakis(pentamethylene- tetrazole) transition Metal Perchlorate Complexes. . . . . 82 Infrared Absorption Studies of the Tran- sition Metal Complexes of Pentamethylene- tetrazole (5000- 680 cm" '1 region) . . . . . 82 Hexakis(pentamethylenetetrazole)- transition Metal Perchlorates. . . . . . 83 Tetrakis( entamethylenetetrazole)- copper(II Perchlorate . . . 97 Bis(pentamethylenetetrazole)copper(I)° Perchlorate... . . . . . . . . . . . . . 99 TABLE OF CONTENTS - Continued III. Far Infrared Studies of the Transition Metal Complexes of Pentamethylene- tetrazole (680- 180 cm-1 region). . . . Pentamethylenetetrazole . . Anhydrous Sodium and Silver Perchlorate Hexakis(pentamethylenetetrazole)- transition Metal Complexes . . . . . Tetrakis(pentamethylenetetrazole)- c0pper(II) Perchlorate . . Bis(pentamethylenetetrazole)copper(I)° Perchlorate. . . . . . . . . . . . . . SUMMARY AND CONCLUSIONS . . . . . . . . . LITERATURE CITED. . . . . . . . . . . . . APPENDICES. O O O 0 O O O O O O O O O I C I - Attempted Determination of the Step- wise Formation Constants of Hexakis- (pentamethylenetetrazole)COpper(II) Perchlorate in Nitromethane. . . . II - Electron Spin Resonance of Hexakis- (pentamethylenetetrazole)- manganese(II) and c0pper(II) Per- chlorates . O O O 0 C C 0 9 O 0 C 0 vi Page 101 102 102 102 115 115 118 136 l#6 1&6 1&9 TABLE II. III. IV. VI. VII. VIII. IX. LIST OF TABLES Page The Physical Properties and Transition Metal Analysis Data of the Transition Metal Com- plexes of Pentamethylenetetrazole. . . . . . . 31 Electronic Absorption Spectra (in om‘l) of the Transition Metal Complexes of Penta— methylenetetrazole . . . . . . . . . . . . . . 53 Magnetic Susceptibility Data of the Transi- tion Metal Complexes of Pentamethylene- tetraZOleO 0 O O O O O 0 0 0 (I 0 O O 0 O O O o 65 Calculated Magnetic Moments and Unpaired Spins of the Transition Metal Complexes of Pentamethylenetetrazole. . . . . . . . . . . . 66 Diamagnetic Correction Values. . . . . . . . . 67 Relative Intensities versus d-spacings for the Hexakis(pentamethylenetetrazole)- Transition Metal Perchlorate Complexes . . . . 71-72 Relative Intensities versus d-spacings for the Isomorphous Replacement of 1% Copper(II) and 1% Manganese(II) in the Hexakis(penta- methylenetetrazole)zinc(II) Perchlorate Complex Lattice. . . . . . . . . . . . . . . . 73 Relative Intensities versus d—spacings for the Hexakis(pentamethylenetetrazole)- Transition Metal Perchlorate Complexes . . . . 7h-75 Standard Deviation Calculations for the Tabulated d-Spacings of All the Hexakis- (pentamethylenetetrazole) Transition Metal Complexes (Tables VI; VII and VIII). . . . . . 76 Relative Intensities versus dwspacings for the Tetrakis(pentamethylenetetrazole)conner(II) Perchlorate Complex. . . . . . . . . . . . . . 77 vii _.__—__ fl- ‘ __.. LIST OF TABLES - Continued TABLE Page XI. Relative Intensities versus d-s acings for the Bis(pentamethylenetetrazolechpper(II) Perchlorate Complex. . . . . . . . . 78 XII. Infrared Absorption Bands (in cm'l) of Transition Metal Complexes of Penta- methylenetetrazole (Nujol Mulls) . . . . . . . 8h-87 XIII. Far Infrared Spectra (in cm‘l) of Tran- sition Metal Complexes of Penta- methylenetetrazole . . . . . . . . . . . . . . 103-104 XIV. Electron Spin Resonance Data for Some Mn(II) Complexes. . . . . . . . . . . . . . . . . . . 150 XV. ESR Data for Cu(II) Complexes with Nitrogen Bonding Ligands . . . . . . . . . . . 155-156 V111 LIST OF FIGURES FIGURE Page 1. Infrared absorption Spectra. Nujol mull. Cu(PMT)4 (010) precipitated from acetic acid an Cu(PMT)H(C104) obtained from CHClB-CC14 mixture. . . . . 32 2. Infrared absorption spectra. Nujol mull. Cu(PMT)6 (C10) precipitated from DMP and Cu(PMT T3 010 re- crystallized from CHé13-0314 mix- ture 9 O O O O O O O O O O O O O O O 33 3. Infrared absorption Spectra. Nujol mull. Ni(PMT) 6(C104) precipitated from DMP and Ni(PMT)6(ClO4)2 precipi- tated from water. . . . . . . . . . . . . 35 4. Molar ratio study in nitromethane of 5 x 10‘ M Cu(ClO4)2°6 H20 with PMT in nitromethane at 700 min . . . . . . . . . 40 5. A continuous variation study at various wavelengths of the Cu(ClO4)2-6 H O-PMT system in nitromethane having a otal analytical concentration of 2.5 x 10'2 M. #1 6. A continuous variation study at various wavelengths of the Cu(Cth)2-6 H20-PMT system in nitromethane having a total analytical concentration of 5.0 x lO'ZM . #2 7. SBectrOphotometric study of 1.0 x 10‘ M Cu(0104)2° 6 H20 in nitromethane upon addition of PMT. . . . . . . . . . . 44 8. A Spectrophotometric study of 1.0 x 10 2 M Cu(PMT)6 (C10 )2. in nitromethane upon addition of PMT. . . . . . . . . . . #5 9. A SpectrOphotometric study of 1.0 x 10"2 M Cu(PMT) 4(ClO4)2 in nitromethane upon addition Of PMT O O O O O O O O O O O O 0 “6 10. The vis ble and near infrared Spectra 3f 1 x 10‘ M Co(PMT)§(ClOH 4) and5 x 10 M Co(c1o4726 H20 n nitromethane . . . #8 ix LIST OF FIGURES - Continued FIGURE 11. 12. 13. 1h. 15. 16. 17. 18. 19. 20. 21. The vis ble and near infrared spectra of 1 x 10- M Ni(PMT)6(C104)2 and 6.72 x 10-3 M Ni(0104)206 H20 in nitromethane . . The vis ble and near infrared Spectra of 1 x 10‘ M Cu(PMT)4(0104)2, and Cu(C104)2-6 H20 in nitromethane. . . . . . The reflectance spectra of Fe(PMT)6- (0104)2 and Co(PMT)6(ClO4)2. . . . . . . . The reflectance Spectra of Ni(PMT)6- (0104) preci itated from DMP and Ni(PMT§6(CIO4§2 precipitated from water. . The reflectance Spectra of Cu(PMT)6- (0101+)2 and. Cu(PMT)4(C104)2o e o e o o e e The thermogravimetric analysis of Cu(PMT)4(C104)2, Cu(PMT)6(CIO4)2, and Mn(PMT)6(C104)2. e o e e o o o e o o e e 0 NMR absorption Spectra of PMT in yridine, Zn(PMT) (0104)2 in D20 and Cu(PMT 2C104 ‘ in Pyri inc 0 C O O O O O O O O O O O O O 0 Infrared absorption Spectra of PMT as potassium bromide pellet and of PMT as. NuJOJ- mull O O O O O O O O O O O O O O O 0 Infrared absorption Spectra. NuJol mull. Mn(PMT)6(CIO )2 - 8:1 ratio method in DMP and Mn(PMT)6(0104)2 - H:1 ratio method in D O O O O O 0 O C 0 O O O O O O O O I O 0 Infrared absorption Spectra. NuJol mull. Fe(PMT)6(C10 )2 - 8:1 ratio method in DMP and Fe(PMT)6 0104)2 - 4:1 ratio method in D O O. O O O O O O O O O O O O O O O O O 0 Infrared absorption spectra. Nujol mull. Fe(PMT)S(ClO ) - 8:1 ratio method in DMP and Fe( MT)6(C204)3 - #:1 ratio method in D O O I O O O O O O O O O O O O O O Page 50 52 55 56 57 59 81 88 9O 91 -__ _. _,__- LIST OF FIGURES - Continued FIGURE 22. 23. 2h. 25. 26. 27. 28. 29. 300 31. Page Infrared absorption Spectra. Nujol mull. Ni(PMT)6 (ClO - 8: 1 ratio method in DMP and Ni( SMT)6(CE04)2: - 4:1 ratio method in DMP o e e e e o o e e e e o o o 92 Infrared absorption Spectra. Nujol mull. Co(PMT)6 (C10 - 8: 1 ratio method in DMP and Co( SMT)6(CIO4)2: - 4:1 ratio method in DMP. o e o o o o o o o e e o o 93 Infrared absorption Spectra. Nujol mull. Zn(PMT)6 (010 2 - 8:1 ratio method in DMP and Zn(PMT)6(CIO4)2 - 4:1 ratio method in DMP. O O O 0 O O C O C O U C O O O I O O 0 9“ Infrared absorption Spectra. NuJol mull. Cu(PMT)6 (010 2 - 8:1 ratio method in DMP and Cu(PMT)4(ClO4)2 - h:l ratio method in D . . . . . . . . . . . . . . . . . . . . 95 Infrared absorption Spectra. Nujol mull. Cu(PMT)4 (010 - precipitated from HOAc and Cu(PMT)4(C104)2 - prepared in CHBNOZ . 98 Infrared absorption Spectra. Nujol mull. Cu(PMT) 0104 - 2:1 ratio method in DMP and Cu(PMT)” 2C104 - prepared from CHBNOZ and hOt water. 0 0 O O O O O O O O O O O O 100 Far infrared absorption Spectra. Nujol mull. Pentamethylenetetrazole and 1- methyltetrazole. . . . . . . . . . . . . . 105 Far infrared absorption Spectra. NuJol mull. 5-methyltetrazole and 5-ethy1- tetraZOJ-eO O O O O O O O 0 O O O O O O O O 106 Far infrared absorption Spectra. Nujol mull. 5-M-pr0py1tetra201e and 5-Mrpenty1- tetr3201eo O O O O O O O 0 O O O O O O O O 107 Far infrared absorption Spectra. Nujol mull. Sodium perchlorate and Silver perchlorate. . . . . . . . . . . . . . . . 108 xi LIST OF FIGURES - Continued FIGURE 32. 33. 34. 35. 360 37. 380 39. Far infrared absorption spectra. Nujol mull. Pentamethylenetetrazole and MH(PMT)6(C104)2. o o e e e o o e e o e 0 Far infrared absorption Spectra. mull. Fe(PMT)6(0104)2 and Nujol Fe(PMT)6(ClO4)3. . . . . . . . . . . . . Far infrared absorption spectra. mull. Co(PMT)6(ClOM)2 and NuJol Ni(PMT)6(ClOL},)20 o o o o o o e o o e o 0 Far infrared absorption Spectra. mull. Cu(PMT)6(C104)2 and Zn(PMT)6(ClO4)2. . . . . . ... . Far infrared absorption Spectra. mull. Cu(PMT)4(0104)2 and NuJol NuJol Cu(PMT)2ClOl+ o e e o e e e e o o e e o o The proposed structural configuration of the hexakis-(pentamethylenetetrazole)- transition metal perchlorate complexes . The ESR Spectrum of 1% Mn(PMT)6(C104)2 in zn(PMT)6(ClOLI,)20 e e e e e e e e e e e o o The ESR Spectra of undiluted Cu(PMT)4 (C104)2 and Cu(PMT)6(CIO4)2 powder . . . . xii Page 110 111 112 113 116 135 151 157 I. HISTORICAL General Tetrazoles are five membered, heterocyclic ring compounds which contain one carbon and four nitrogen atoms linked by three Single and two double bonds. The tetrazole ring is numbered so the nitrogen single bonded to the carbon is the one position. The remaining three nitrogenS are then numbered consecutively two through four with the carbon at the five position. The parent compound may exist in tautomeric forms I and II (1.2). H H H 1 5/ 1 5/ _ C N“: C , \\ a N/ M 21k:N Nh ‘ \\\N fly 3 3 I II It has been found that 97% of an equilibrium mixture of I and II exist in the form I (3). The tetrazole ring is unusual among cyclic systems in that it offers only two points of substitution--in position 1 or 2 and in position 5. Pentamethylenetetrazole III represents a Special group of substituted tetrazole derivatives in which the penta- methylene chain forms part of a seven membered ring fused to the tetrazole ring. 8 H C H\ 7 HCIIH HCIL'H 9 6 HCH HCH 10 5\b‘__'fi/1 I I? \N 2 \\\§¢§; III Pentamethylene tetrazole was first prepared by Schmidt (k) in 1925. His synthesis is described in detail elsewhere (5). Schmidt also reported the preparation of one of the first metal- PMT complexes--a precipitate which formed when an aqueous solution of mercury (II) chloride was added to a solution of PMT in water. Chemical investigations of tetrazoles have shown that they are nucleOphilic reagents and that their nucleOphilic character varies with the nature of the groups substituted on the ring. In this respect, substituted tetrazoles present an especially interesting problem both for the pharmacologist and the chemist. AS drugs they possess a wide spectrum of neurotropic activities from strong convulsants (such as PMT) to depressants (e.g. 1- methyl-5-aminopheny1tetrazole). In a series of papers (6-10) Gross and Featherstone have described in detail the pharmacological properties of a wide variety of tetrazole compounds. They attempted to correlate pharmacological action with structure change of the tetrazole molecule. In a later study (11) they attempted to correlate the absorption Spectra of a series of substituted tetrazoles with the pharmacological action of the compounds. Analytical Studies on PMT Most of the tetrazole research has been in the area of synthesis and the determination of the pharmacological properties of these neurotropic drugs. Little work, however, has been done with respect to the physicochemical and especially the donor prOperties of tetrazoles. Most of the studies have been con- cerned with the identification.)separation, and determination of PMT (12-30). At present, the most widely used analytical procedure for the quantitative determination of PMT seems to be a precipitation of its more or less insoluble complexes with various inorganic salts. Zwikker (14) prepared addition compounds of PMT with tetrahydrogenhexacyanoferrate(II), trihydrogenhexacyanoferrate(III) and some salts of cadmium(II), mercury(II), zinc(II), and copper(I). A copper(I)-PMT-comp1ex having the approximate composition PMT¢2 CuCl was precipitated from a hydrochloric acid solution of copper(I) chloride. This compound served aS the basis for the first analytical procedure for the determination of PMT. He also found that PMT could be extracted quantitatively from a saturated aqueous ammonium sulfate solution into carbon tetrachloride. 4 Paulsen (31) modified the copper(I) chloride-PMT complex method by dissolving the precipitate in a hydrogen peroxide solution and measuring the amount of copper complexometrically. Hbrseley (21) regarded this gravimetric method as being rather cumbersome and claimed that the procedure was simplified by precipitating PMT as the mercury(II) chloride complex. Dister (32) compiled a detailed report on the physical and chemical prOpertieS of PMT and repeated some of this work. Hewever. much of the work reported was qualitative. Lindgren et a1. (33). proposed a determination based on the precipitation of the PMT in a 3:2 isopropanol-water mixture with excess cadmium chloride. The cadmium in the precipitate was then titrated complexiometrically. In his precipitation and ex- traction studies of PMT, Golton (5) concluded that neither of these above methods yields satisfactory results. Kolusheve and Nino'o (34) precipitated-a double salt of PMT having the formula (PMT)4°3 CdC12 from a hydrochloric acid solution. The precipitate was removed by filtration and the ex- cess cadmium ion titrated complexiometrically,but the method was not quantitative. Troop (35) determined PMT by precipitating it in an aqueous solution as the silver-PMT-phosphotungstate salt, Ag3(PMT)4Pw1204oo4 32° (solubility in water is 8.3 1 0.6 x 10"6 moles per liter). using an excess of silver nitrate. After the precipitation was complete, the excess silver ion was titrated potentiometrically with a standard hydrochloric acid solution. The author claimed an accuracy of ten parts per thousand. Acid-Base Studies Olivera-Mandala (1.36) was one of the first investigators to study acidic and basic dissociation constants of tetrazole derivatives. The acidic dissociation constants were obtained by means of conductivity measurements while hydrolysis constants of l-Substituted tetrazole hydrochlorides were determined from the influence of these substances on the rate of hydrolysis of methyl acetate. Tetrazole and 5—substituted tetrazoles generally behave as acidic substances and Show a range of acid strengths. In aqueous solution tetrazole has a pKa of 4.93 (1.37) while the pKa of 5-phenyltetrazole is 4.5 (38.39). Both can be titrated with strong base using phenolphthalein as the indicator. It is probable that all 5-Substituted tetrazoles are acids having pKa values of 7 or less. The 5-Substituted tetrazoles can also act as bases due to the presence of three other nitrogen atoms. Their basic strength, as calculated from the hydrolysis constants of the respective hydrochlorides, appears to be of the same order of magnitude as that of aniline (40). Herbst and Mihina (41) determined the pKa values for 5-phenyl and 5-toly1tetrazole potentiometrically using a water-methanol mixture of varying composition. They noted that these compounds were stronger acids than the benzoic acid or the respective toluic acids. Unfortu- nately these relative values may be in doubt Since no account was made for the changing liquid Junction potential when the Solvent composition was changed. Herbst and Wilson (38) found that the apparent acidic dissociation constants of the 5- alkyltetrazoles were about 10 to 20 percent of those for the corresponding carboxylic acids. Herbst and Garbrecht (42) prepared 5-acetylaminotetrazole which can be titrated as a weak monoprotic acid. They Speculated that the compound could quite possibly behave as a diprotic acid in a nonaqueous media. Maher and Yohe (43) titrated 5-acetylaminotetrazole potentio- metrically uSing ethylenediamine as the solvent and sodium aminoethoxide as the titrant. They were able to determine the two endpoints with the second hydrogen having about the same acid strength as phenol in the same solvent. Tetrazoles substituted in the one position do not behave as acids. Stolle 33 2M. (44) reported that they removed the 5-carbon hydrogen from l-phenyltetrazole with methyl magnesium iodide in ether to form l-phenyltetrazolemagnesium iodide.' However, in this laboratory their results could not be dupli- cated (45). Recently, Garber (46) has successfully removed the 5-carbon hydrogen using n-butyl lithium in anhydrous tetrahydrofuran. Pentamethylenetetrazole. substituted PMT. and 1-5 dialkyl tetrazoles have surprisingly weak basic properties in aqueous solutions. The first hint of the basic character of these com- pounds came from the distribution studies performed by Dister (32) in which he noted that the distribution coefficient (organic)/(aqueous) was larger for basic media. This would indicate that PMT can behave as a weak base. Popov and Holm (47) te I '\.J titrated PMT potentiometrically in glacial acetic acid with perchloric acid in the same solvent and found that PMT does possess weak basic properties in acetic acid. A more detailed treatment of the proton affinity of PMT, substituted PMT, and 1-5 dialkyl tetrazoles by Popov and Marshall (48,49) was carried out in anhydrous formic acid to enhance the basic character of these weak bases. They were able to determine potentiometrically the pKa values of these tetrazoles in this solvent. Dipole Moment Studies Jensen and Friediger (50) determined the dipole moment of tetrazole, 5-aminotetrazole. and 1-methyltetrazole in dioxane (D) or benzene (B). The respective measured dipole moments were 5.ll(D). 5.71(D) and 5.38(B) debyes. These fairly large moments were attributed to the contribution of various charge separated structures which are characteristic for the tetrazole ring system. Kaufman, Ernsberger and McEwan (51) determined the dipole moments of twelve substituted tetrazoles and also attributed the origin of the respective dipole moments to the resonance con- tribution of a number of charge separated structures. The ex- perimental dipole moments of l and 2 ethyl tetrazole are 5.46 and 2.65 debyes reSpectively, which implies that the tetrazole tau- tomer represented by structure I, (page 1) having a dipole moment of 5.11 debyes, predominates. These authors also established that such measurements are not suitable for recognizing meso-ionic compounds 1.2. compounds which exhibit aromatic characteristics and can be represented only as resonance hybrids of a large number of contributing ionic forms. Lounsbury (3) undertook a theoretical examination of the dipole moments of tetrazoles. His results Show that the largest contributors to the difference in the dipole moments of 1 and 2 substituted tetra- zoles lies in the difference in the vectorial summation of the lone pair moments and the sigma moments. In order to obtain the observed apparent dipole moment of 5.11 debyes for tetra- zole from a mixture of I and II (see page 1), 97% of an equilibrium mixture of 1-5, and 2-5 tetrazole must exist as the 1-5 tautomer. This conclusion also agrees with the results of anNMR study (2) of the chemical shifts of the carbon bound proton on the tetrazole ring in tetrazole and 1 alkyl substituted tetrazoles. Kaufman and Woodman (52) determined the dipole moments of various chloro-, bromo-, and nitrophenyl tetrazoles to investi- gate the geometry of the tetrazole ring. POpov and Holm (53) measured the dipole moments of PMT, 8-§ggebutyl PMT, 8-Efbuty1 PMT and 1-cyclohexyl-5-methy1tetrazole in benzene solution obtaining the values 6.74, 6.18, 6.20, and 6.00 debyes for the respective compounds. Coogdination Compounds Since tetrazole and 5-Substituted tetrazoles are acid, many of the corresponding metal salts have been easily prepared in aqueous solution. Thiele and Ingle (54,55) neutralized a dilute aqueous solution of tetrazole with sodium hydroxide and precipi- tated very Slightly soluble crystals of sodium tetrazolate mono- hydrate. The water of cyrstallization could not be removed even at reduced pressures. When barium hydroxide was used to neutralize the dilute tetrazole solution, barium tetrazolate trihydrate crystals were isolated after the excess barium ion was precipitated with carbon dioxide. Bladin (56) prepared the first Silver salt of tetrazole and 5-substituted tetrazoles by adding hot silver nitrate solution to an aqueous solution of the re- Spective tetrazole. This reaction has since been used as an identification and purification method. The copper(II) salt of tetrazole was prepared in a similar manner. Strain (57) reacted tetrazole with gaseous ammonia to produce ammonium tetrazolate and prepared calcium tetrazolate by allowing tetrazole to react with metallic calcium in liquid ammonia. These early workers con- sidered the metal tetrazolates to be Simple salts. However, recent studies have shown that some of them are actually coordi- nation compounds (47,58 and 59). Herbst and Garbrecht (42) prepared the silver salts of 5-substituted tetrazoles by adding equimolar amounts of Silver ion to solutions of the tetrazolate ion. Such complexes have been used to characterize 5-substituted tetrazoles (41). Olivera-Mandala and Alagna (60) presumably prepared one of the first true coordination complexes involving a tetrazole derivative. Upon the addition of platinum(IV) chloride 10 to an alcoholic hydrogen chloride mixture containing 1-ethyl tetrazole, a canary yellow precipitate characterized as bis- (l—ethyltetrazole)-tetrachlor0platinate(IV) was isolated. In order to study the electron donor properties of PMT complexes, P0pov, Bisi, and Craft (61) determined Spectro- photometrically the formation constants of the 1:1 PMT complexes: iodine monochloride, iodine monobromide, and iodine in carbon tetrachloride solution. Only the PMT-1C1 complex could be obtained as a solid crystalline form which could be purified by recrystallization from chloroform. Popov, Wehman and Vaughn (62) extended this work by the spectr0photometric investigation of the complexes of iodine monochloride with 7-methy1, nggg- butyl and B-Mgbutyl PMT. Repeated attempts were made to isolate the respective solid iodine monochloride complexes of the above PMT derivatives, however, only oily residues which decomposed on standing were obtained. The formation constants of the three complexes were determined, and in all cases the complexes are Slightly stronger than the correSponding complex for the un- substituted PMT. Person, Humphrey, Deskin and Popov (63), in their infrared spectra study of iodine monochloride charge transfer complexes, found that the Spectrum of the I-01 funda- mental stretching vibration was very sensitive to the strength of the interaction between the halogen and the donor molecule with which it is complexed. On this basis the PMT molecule was concluded to be a moderately strong donor. Rheinboldt and 11 Stelliner (64), Dister (32) and Zwikker (14) have reported the preparation of PMT-Silver complexes; however, the stabilities of complexes in water were never determined. POpov and Holm (47) prepared Silver complexes in acetonitrile, having the general formula, (Tz)2AgN03, with PMT, substituted PMTS and l-cyclo- hexyl-5-methyl tetrazole. The stabilities of these complexes were determined potentiometrically in acetonitrile, and the approximate formation constants were of the order of 102. Only the (PMT)2AgN03 complex was obtained in the crystalline form by the Slow evaporation of an aqueous solution of the complex. This demonstrates that loSS of the ring hydrogens is not necessary for coordination to occur. The coordination could occur either through the electrons of the tetrazole ring or through one of the nitrogen atoms of the ring. At the present time, however, no clear cut evidence is available to unambiguously distinguish be- tween the two possibilities. Brubaker (59) prepared and characterized two crystalline forms of bis-(5-aminotetrazolato)-c0pper(II). The method of con- tinuous variation clearly indicated that a 1:2 metal to tetrazole complex was formed in solution. The hypsochromic Shift and accompanying hyperchromic effect suggest .coordination rather than Simple salt formation. Further studies showed that Similar behavior is observed using tetrazole, 5-phenyltetrazole and l- ethyltetrazole. Brubaker found that there is very little inter- action between the copper(II) ion and 1-5 dimethyltetrazole. 12 This fact, together with the relatively low formation constant values for (PMT)2AgN03 («102) (47), indicates that a replacable ring hydrogen is required to form this type of complex. Brubaker and Daugherty (65) found that nickel(II) forms only impure and poorly characterized complexes when its salts react with various 5-Substituted tetrazoles. COpper(II) com- plexes (66) with 5-Substituted tetrazoles are obtained in good purity simply by mixing aqueous solutions of the reactants. Brubaker and Gilbert (67) prepared complexes of various 1-substituted tetrazoles with cobalt(II), nickel(II), platinum(II) and zinc(II) chlorides. The solid complexes, with the exception of the zinc complex, are insoluble in common solvents. They decompose upon heating without melting which suggests the possibility of polymeric structures. Brubaker (66) suggests the following three possible methods of coordination between metal ions and tetrazoles: 1. One of the nitrogens of the tetrazole ring acts as a Lewis base and donates its pair of electrons to the central metal ion. 2. The central metal ion may coordinate to the arelectron system of the tetrazolate anion. 3. Since the tetrazolate anion seems to satisfy two coordination sites on the coPper ion, coordination could occur by the formation of bonds to two different nitrogen atoms of the tetrazole ring. 13 Jonassen 23 3;. (68) prepared microcrystalline complexes of iron(II) conforming to the general formula Fe(tetrazolato)2o2 H20. They used the anions of 5-chlorotetrazole, 5-trifluoromethyl- tetrazole and 5-nitrotetrazole. Using infrared and MUSsbauer studies, they prOposed the formation of an analog to ferrocene when the tetrazole has strongly electronegative groups on the carbon. Jonassen, Harris and Archer (69) obtained reflectance spectra of divalent metal ions in 5-trifluoromethyltetrazole complexes. Based on the correlation of these reflectance Spectra with previously obtained magnetic susceptibility and visible solution Spectral data, they re-evaluated the proposed structure of the Fe(tetrazolato)2°2H20 complexes. The new experimental evidence indicated that the structure of the iron(II) and reSpective cOpper(II), cobalt(II), and nickel(II) 5-trifluoro- methyltetrazole complexes are octahedral or distorted octahedral o-bonded complexes involving coordination by tetrazolyl anion and water. Jonassen, Terry and Harris (70) showed the 5-tri- fluoromethyltetrazolyl anion to be a weakly coordinating ligand in aqueous solution. The transition metal ions used in their investigation were cobalt(II), nickel(II) and c0pper(II), which again shows that the tetrazolyl ion can participate in coordi- nation with some transition metal ions. II. EXPERIMENTAL REAGENTS Pentamethylenetetrazole (PMT) A11 PMT used in this investigation was obtained from the Knoll Pharmaceutical Corporation under the registered name "Metrazol." The PMT was purified by recrystallization from anhydrous ether. The crystals obtained were washed with small volumes of chilled ether. Residual ether was removed under vacuum and the crystals were stored in an evacuated desiccator over phosphorus pentoxide. The melting point of the crystals was 60.5-6l°C. The literature value iS 61°C (61). Nitromethane Nitromethane was first passed through a cationic ion ex- change unit prepared in the following manner: Seventy-five grams of Amberlite IR-120 resin (hydrogen form) were Slurried with anhydrous methanol. The methanol was decanted and dis- ‘carded. This process was repeated several times and then the resin was transferred to a column 2 cm. in diameter and 25 cm. in length. Then the resin in the column was washed first with one liter of anhydrous methanol at a rate of 1-2 ml. per minute, and then with two 300 ml. portions of nitromethane. The eluate was discarded. The crude nitromethane was then passed through the column at a rate of 2-5 ml. per minute. (71). A vapor phase chromatogram of the purified material gave a single sharp 14 15 peak using a Beckman GC-2 chromatograph equipped with a silicone 30 column (current 200 ma, attenuation 10, temperature 70°C). The water content, which was determined by a Karl Fischer titration, correSponded approximately to a 10"3 M solution. 2,2-Dimethggyprgpane (985) This reagent was of technical grade and used without further purification. It was obtained from the Dow Chemical Co. Barium Oxide This chemical was obtained from Barium and Chemicals, Inc. and was the 1/4" x 1/8" screened mesh variety. Analytical Methods Copper Determinatigg The following two methods were used: Iodometric Pentamethylenetetrazole reacts with iodine and, therefore, interferes in the iodometric determination of the copper in the cepper-PMT complexes. The interference was re- moved by the following method. The complex was dissolved in 12 M nitric acid and the solution was boiled gently for ten minutes to decompose the PMT. Then, 10 m1. of 12 M sulfuric acid was added and the solution evaporated to dryness overnight on an 80°C hot plate. The residue was redissolved in 100 ml. of distilled water, neutralized to pH 7 with sodium hydroxide, and then acidified with acetic acid to the approximate pH of 4. After the addition of potassium iodide, the liberated iodine was titrated with standard thiosulfate solution (72). 02‘. I r'\ ,.. .Q'l I‘V. «1 ._‘- C) H “A “.V ~ I _‘-\.' ’1) Complexometric An aqueous solution of the respective cOpper complex was made basic to a pH of 8-9 with ammonia. Murexide (ammonium purpurate) indicator was added and the solution was titrated with 0.01 M EDTAauntil the color changed from yellow to violet (73). Nickel Determination An aqueous solution containing the complex was neutralized to pH 7 with sodium hydroxide, then murexide indicator and 10 ml. of l‘M ammonium chloride was added. The solution was titrated with 0.01 M EDTA. Just prior to the end point, 10 ml. of con- centrated ammonia was added and the titration continued to the end point when the color changed from yellow to bluish violet (73). Cobalt Determination An aqueous solution containing the complex was made slightly acidic (pH 6). Murexide indicator was added and the pH of the solution adjusted with ammonia until the color of the indicator changed from orange to yellow. The solution was then titrated with 0.01 M EDTA to a sharp color change from yellow to violet (73). Zinc Determination An aqueous solution containing the complex was neutralized to pH 7 with sodium hydroxide. Then, 2 ml. of pH 10 buffer, and Eriochrome Black T(l-[l-Hydroxy-Z-naphthylazo]-6-nitro-2- \— a EDT%.= Ethylenediamine tetraacetic acid. the 1 nitr: indi. 1? naphthol-4-sulfonic acid sodium salt indicator) was added. The solution was then titrated with 0:01.fl EDTA until the color changed from red to blue (73). Iron Determination Several attempts were made to determine the iron content of the iron complexes but they were unsuccessful. The carbon, nitrogen, hydrogen, and perchlorate analyses, however, are good indications of the stoichiometry of these complexes. ‘ Manganese Determination An aqueous solution containing the complex was made weakly acid to pH 5. Ascorbic acid (0.5 grams) was added and the mix- ture was warmed over a Meeker burner. After five minutes the solution was neutralized with sodium hydroxide and 5 m1. of 0.1 M zinc sulfate, 2 ml. of pH 10 buffer and several drOps of Eriochrome black T were added. The solution was then titrated with 0.01 M EDTA to the red-blue color change (73). Carbon, Hydrogen, and Nitrogen Analyses The Spang Microanalytical Laboratory, Ann Arbor, Michigan, determined the carbon, hydrogen and nitrogen. percentages in the transition metal complexes of PMT. ngchlorate Determination The complex was first dissolved in 75 ml. of 0.5 M sodium chloride solution (which makes the precipitate more granular), £350 #5 er. V 18 and then heated to boiling. The precipitation was carried out in a hot solution by adding an excess of 0.1 M tetraphenyl— arsonium(III) chloride. The precipitate was allowed to digest for 6 hours at room temperature, then filtered, washed several times with ice water, dried at 110°C, and weighed as tetra- phenylarsonium(III) perchlorate (74). Water Determination The water content of the transition metal complexes of PMT was determined by Karl Fischer titration. The complexes were dissolved in purified nitromethane or acetone and the water reacted with the Karl Fischer reagent (75). Instrumentation The following instruments were employed in making the apprOpriate measurements. Cary Model 14 recording Spectrophotometer was used to obtain near infrared, visible, and ultraviolet absorption spectra. Beckman IR5A infrared Spectrophotometer was used to obtain infra- red absorption Spectra utilizing KBr pellets and nujol or fluorlube mulls. Ag_Alpha Scientific Laboratories AL 7500 M Electromagnet and A; 7590 PS Power Supply equipped with a Mettler single pan balance was used for the magnetic susceptibility measurements. A Varian A60 nuclear magnetic resonance Spectrometer was used to obtain the NMR spectra. 19 A Varian model V-4500 spectrometer having a 100 Kc field modulator was used to obtain the ESB Spectra. The magnetic field was measured with a proton nuclear magnetic resonance gaussmeter. Beckman GC-2 Gas Chromatograph was used to check the purity of the nitromethane. Fisher-Johns Meltipg Point Apparatus was used to obtain all melting points. A North American Philips Company, type 12045, X-ray generator equipped with a North American Philips Company, type 52056, camera was used to obtain the X-ray powder diffraction photographs. A Perkin-Elmer Modelg301 Far-Infrared Double-Beam Spectro- photometer which utilizes various choppers, mirrors and filters was used to obtain the far-infrared Spectra of the respective complexes. Beckman DU Spectrophotometer equipped with a reflectance attachment was used to record the reflectance Spectra. These Spectra were obtained by Professor Luigi Sacconi, Institute of Inorganic Chemistry, University of Florence, Italy. Experimental Procedures Temperature Control Unless otherwise stated, no temperature control was employed during any of the measurements. All standard solutions were prepared at room temperature of approximately 25°C. 20 Fisher-Johns Melting Point Apparatus Calibration The Fisher-Johns melting point apparatus was calibrated using appropriate Arthur H. Thomas Company (Philadelphia, Pa.) micro-melting point standards. Thermometer Stem Correction The following formula was used to correct all melting points obtained during this study (76). K = (0.000154)(t-t') N where: K = correction in degrees added to temperature read t = temperature read t' = average temperature of the exposed column of mercury N = the length, measured in degrees, of the thread of mercury exposed between the electrical heating block and the point t. Preparation of Solutions All solutions of PMT in nitromethane were prepared from weighed amounts of PMT. Solutions of copper(II) perchlorate hexahydrate were prepared from weighed amounts of this compound. The copper in a 10 ml. aliquot was then extracted into water and the copper titer determined iodometrically (7?). Selection of a Copper(II) Salt for the§pectrophoto~ metric Study of the Donor PrOperties of PMT Solubility of Various Copper Salts in Purified Nitromethane In order to find a copper salt which would be the best 21 source of copper(II) ions in nitromethane for the spectrophoto- metric studies of the donor prOperties of PMT, the following compounds were investigated: (1) Anhydrous copper(II) chloride -~ CuCl2 (2) Anhydrous copper(II) bromide -- CuBr2 (3) Anhydrous copper(II) sulfate -- CuSO4 (4) COpper(II) acetate monohydrate -- Cu(C2H302)2°H20 (5) COpper(II) nitrate trihydrate -- Cu(N03)2° H20 (6) Copper(II) perchlorate hexahydrate -— Cu(C104)2'6H20 (7) Copper(II) pntoluenesulfonate -- Cu(C7H7SO3)2 All of the above copper salts with the exception of copper(II) p-toluene sulfonate are commercially available. Copper(II) p-toluene sulfonate was prepared by adding dry cOpper(II) carbonate directly to a saturated aqueous solution of p-toluene sulfonic acid until the pH was about 3.5. The filtered solution was then evaporated on a steam bath. The product was recrystallized twice from hot water at 110°C for four hours (78). Analysis: Calculated: Cu, 15.91%: C. 41.46%; H, 3.45%; 3, 15.78%. Found: Cu, 15.80%; c, 40.37%: H. 3.66%. n 5. 14.41%. The anhydrous cOpper(II) sulfate and copper(II) p-toluene sulfonate were insoluble in nitromethane and there- fore could not be used in this study. COpper(II) chloride, bromide, sulfate and acetate were eliminated because of the combination of low solubility 22 tel x 10"3 moles per liter) and relatively low molar absorpti- vities 6'20). Furlani, Sgamellotte and Guillo (78) reported that cOpper(II) paratoluene sulfonate was soluble to the extent of 2.0 x 10‘2 M in acetonitrile at room temperature. waever, in this laboratory it was found to be practically insoluble in nitromethane (~2.5 x 10‘“ moles per liter). The Spectrum of a saturated solution of this compound in nitromethane Showed no appreciable absorption in near infrared or visible region, and there was no change on addition of PMT. Therefore it was not studied further. COpper(II) nitrate trihydrate and copper(II) perchlorate hexahydrate dissolve relatively well in nitromethane having approximate solubilities of 3.5 x 10"3 and 5.3 x 10"2 moles per liter respectively. Both of these cOpper salts have molar absorptivities of approximately 20, an absorption maximum at about 780 mpgand each gave a hypsochromic shift with accompanying hyperchromic effect upon addition of PMT. Copper(II) perchlorate hexahydrate was ultimately selected for this study primarily because of its high solubility as compared with the other copper salts. Attempted Preparation of Anhydrous Copper(II) Perchlorate In order to investigate the extent of complexing ability of PMT towards copper(II) ions, anhydrous coPper(II) perchlorate was used because a hydrated salt would introduce water into the system. 23 Since water is a fairly strong electron donor, it would effectively compete with PMT (a weak donor) for the coordination Sites of the cOpper ion. The following methods were used in an attempt to prepare anhydrous copper(II) perchlorate, starting with copper(II) perchlorate hexahydrate. 1. COpper(II) perchlorate hexahydrate was dried in a ' vacuum oven at 75°C and 5 mm pressure for forty-eight hours, as described by Larson and Iwamoto (79). Analysis of the products Showed a c0pper content varying between 17.20 and 19.00 percent. Thus, only the adsorbed water and, at most, two of the Six waters of hydration were removed. 2. 00pper(II) perchlorate hexahydrate was recrystallized from hot nitromethane. The product has a copper content of approximately 19 percent. Again only the adsorbed moisture was removed. 3. Recrystallization of copper(II) perchlorate hexa- hydrate from hot 72% perchloric acid was attempted. This method once again only removed the adsorbed moisture since the copper content was found to be,as before, approximately 19 percent. 4, Copper(II) perchlorate hexahydrate was dissolved in 72% perchloric acid and the excess acid fumed off at 200°C under nitrogen atmosphere. The resulting azure blue powdery material was analyzed for its copper content by iodometric titration while the perchlorate content was determined by gravimetric 24 analysis using tetraphenylarsonium(III) chloride as the precipi- tating agent. The analyzed copper content was 24.23% which was within one percent of the theoretical calculated value for anhydrous c0pper perchlorate. The percentage of perchlorate found was 61.78% or about fifteen percent lower than the theoretically calculated value. Only about 90% of this azure substance dissolved in water or nitromethane. If the respective solutions were made Slightly acidic, the insoluble material dissolved completely. It seems, therefore, that the product was indeed anhydrous copper(II) perchlorate contaminated with a basic c0pper oxide. Attempts to identify the insoluble material by X-ray powder diffraction methods were not successful. Prppapapion of Coordination Compounds of PentamethylenetetrazOIe Since standard drying techniques mentioned above do not remove the water of hydration from transition metal perchlorates, Erley (80) suggested the use of 2,2-dimethoxypropane (hereafter referred to aS DMP) as a dehydrating agent. One mole of DMP reacts endothermically and rapidly with one mole of water of hydration to form two moles of methanol and one mole of acetone. CH3C(0CH3)2CH3 + H20 ————>. CH3GECH3 + ZCH3OH Erley indicated that approximately 96% of the water reacts at 30°C when mixed with DMP in a 1 to 1 mole ratio. 25 Bis entameth lenetetrazole co er(I Perchlorate This complex was prepared by two different methods: (1) Reaction in DMP A solution containing 3.71 grams (0.01 moles) of capper(II) perchlorate hexahydrate in 65 m1. of DMP was prepared with the use of a magnetic stirrer; the mixture was stirred long enough to diSperse the cOpper(II) perchlorate hexahydrate which has limited solubility in DMP. As the mixture was stirred, the color of the copper(II) perchlorate mixture changed from blue to light green. To the mixture was added 3.45 grams (0.025 moles) of dry PMT. A blue oily substance formed immediately. The stirring was continued for approxi- mately three hours during which the oily substance slowly solidified to a white solid. The precipitate was filtered and washed several times with chilled acetone and dried at 110°C. The solid was Slightly soluble in acetone and nitromethane but insoluble in most other solvents. It could not be purified by recrystallization. The compound is stable at room temperature and begins to decompose at 226°C. A positive test for cOpper(I) was obtained when 2,2'- biquinoline was added to a Eebutyl alcohol solution con- taining the complex (81). The solid was identified as a copper(I) complex with the composition Cu(PMT)20104 which was obtained in 48.7% yield. (2) Analysis: Calculated: Cu, 14.46%; C, 32.80%; H, 4.56%; N, 25.51%. Found: Cu, 14.53%; C, 32.41%; H, 5.05%; N. 25.12%. Reaction in Nitromethane To 200 ml. of nitromethane, 3.71 grams (0.01 moles) of vacuum dried c0pper(II) perchlorate hexahydrate were added. After the dissolution of the salt, 3.45 grams (0.025 moles) of PMT were added. The solution was evaporated on a steam bath until only a viscous blue syrup remained. Upon addition of 200 ml. of boiling water, a white, fluffy pre- cipitate was formed which was washed several times with chilled acetone. The product was obtained in a 79% yield. A positive test for cOpper(I) was obtained upon the addition of 2,2'-biquinoline to a E-butyl alcohol solution containing the complex. This white compound (decomposition point 226°C). is slightly soluble in nitromethane and acetone but insoluble in most other solvents; it could not be purified by recrystallization. Analysis: Calculated: Cu, 14.46%; C, 32.80%: H, 4.56%; N, 25.51%. Found: Cu, 14.46%; c, 31.42%; H, 4.55%; N, 25.11%. These two complexes are presumed to be the same as shown by the reSpective elemental analysis and physical prOpertieS (Table I). 26 27 Tetrakis(pgntamethylenetetrazole)coppep(II) Perchlorate (1) (2) This complex was prepared by three independent methods: Reaction in DMP A 3.71 gram sample (0.01 moles) of copper(II) perchlorate hexahydrate was added to 25 m1. of DMP. The mixture was stirred with a magnetic stirrer for about five minutes during which the color of the solution changed from blue to light green. To the solution being stirred, 5.52 grams (0.04 moles) of dry PMT was added. The color of the solution immediately turned blue. After approximately five minutes, a blue precipitate was formed. This was filtered, washed several times with chilled ether, and dried at 110°C. The product was obtained in 96% yield. The melting point of the complex was Spread over a range of 141-14500. Analysis: Calculated: Cu, 7.80%; C, 35.39%; H, 4.95%: N, 27.52%. Found: Cu, 7.60%; c, 35.46%; H, 5.14%; N, 26.73%. Reaction in Anhydrous Acetic Acid To 200 m1. of acetic acid was added 7.44 grams (0.02 moles) of vacuum dried copper(II) perchlorate hexahydrate. After the copper perchlorate was completely dissolved, a stoichiometric amount of acetic anhydride (11.33 ml. or 0.12 moles) required to react with the hydrated water of (3) 28 the copper(II) perchlorate was added; and Cu(C104)2°xH0Ac precipitated as light blue crystals in four to six hours. These crystals were filtered and redissolved in hot acetic acid. An eight molar excess of dry PMT (22.08 grams) was added to the hot solution which turned deep bluei indi- cating complexation. Large, deep blue crystals precipitated in four to six hours. The product (13.0grams) was obtained in a 43.2% yield. The crystals were purified by re- crystallization from acetic acid and dried at 110°C. These crystals melt Sharply at 154°C. Analysis: Calculated: Cu, 7.80%; C; 35.39%; H, 4.95%: N, 27.52%; 01. 8.71%; 0104‘, 24.52%. Found: Cu, 7.71%; c; 35.37%; H; 5.06%; N. 27.39%: 01. 8.85%; 0104“. 24.16%. Reagpion in Nitromethane To 200 ml. of nitromethane was added 3.71 grams (0.01 moles) of vacuum dried copper(II) perchlorate hexahydrate. After the copper perchlorate had completely dissolved, 11.04 grams of dry PMT were added to the solution which turned a deeper blue indicating complexation. The solution was allowed to evaporate Slowly at room temperature and after the volume was reduced to about 25 ml.. royal-blue crystals were formed. The product was obtained in a 52% yield. The crystals were purified by recrystallization from nitromethane and dried at 110°C. These crystals melted over a range.of 14l-145°co 29 Analysis: Calculated: Cu, 7.80%; 0104’, 24.52%. Found: Cu, 7.73%; 0104‘, 24.64%. HexakiS-(Pentametpylenetetrazole)-Cppper(II) Perchlorate A solution was prepared containing 3.72 grams (0.01 moles) of vacuum dried copper(II) perchlorate hexahydrate in 50 ml. of DMP. The mixture was stirred long enough (five to ten minutes) to disperse the copper(II) perchlorate which has a limited solubility in DMP. AS the mixture was stirred,the color of the copper(II) perchlorate in solution changed from blue to light green indicating that dehydration was taking place (82,83). An eight mole excess of dry PMT (11.04 grams) was then added to the solution. A light blue precipitate formed after about five minutes. It was filtered, washed several times with chilled ethyl ether, and then dried at room temperature under vacuum. The product was obtained in 96% yield. The melting point of the complex was ll7.5°C. Analysis: Calculated: Cu, 5.80%; c. 39.65%; H, 5.55%: N, 30.83%: 0104', 18.20%. Found: Cu, 5.71%; c, 39.62%; H, 5.63%: N, 31.10%; 0104-, 18.75%. PpeparationMgfpHexakis~(Pentamethylenetetrazole)-Copper(II) Perchlorate Crystals The complex was recrystallized from carbon tetrachloride in the following manner: To 80 m1. of carbon tetrachloride, in a tall narrow beaker, about 10 ml. of a 0.05 M chloroform 30 solution of the complex was carefully introduced as a layer on top of the carbon tetrachloride. The beaker was then tightly covered to prevent evaporation of the solvent. The carbon tetrachloride diffused through the solution thereby lowering the solubility of the complex. The complex crystallized out of solution overnight as the blue tetrakis(PMT)c0pper(II) perchlorate. The melting point of this complex (153°C) compares favorably with the tetrakiS(PMT)c0pper(II) perchlorate pre- pared in acetic acid (154°C). Infrared Spectra and X-ray powder diffraction likewise indicate that the compounds are identical as shown in Figure l and Tables X and XII. When the solution is allowed to evaporate very Slowly over a period of two weeks, some of the tetrakis(PMT)copper(II) perchlorate is slowly converted to light blue hexakis(PMT)00ppBr(II) perchlorate. These crystals have the same color, melting point, infrared spectrum and X-ray powder diffraction pattern as the hexakis(PMT)cOpper(II) perchlorate complex prepared by the DMP method (Figure 2 and Tables I, VII). Hexakis(pentamethylenetetrazole)nickel(II) Perchlorate This complex was prepared exactly like the correSponding hexakis(PMT)c0pper(II) perchlorate.. A light blue product was obtained in 95% yield. The decomposition of the complex be- gan at approximately 237°C. TABLE I The Physical Properties and Transition Metal Analysis Data of the Transition Metal Complexes of Pentamethylenetetrazole D‘OQthQOU‘m Complex Color Melting Percent Percent Note Point 00 Metal Metal Calculated Found Cu(PMT)2C104 white 226d 14.46 14.53 a Cu(PMT)2C104 white 226d 14.46 14.46 b Cu(PMT)6(0106)2 blue 141-145 7.80 7.60 c Cu(PMT)4(C104)2 blue 154 7.80 7.71 d Cu(PMT)4(C104)2 blue 141-145 7.80 7.73 e Cu(PMT)6(C104)2 1t. blue 117.5 5.80 5.71 f Cu(PMT)6(C104)2 1t. blue 118.0 5.80 5.75 g Ni(PMT)6(0104)2 1t. blue 237d 5.40 5.46 f Ni(PMT)6(C104)2 1t. blue 235d 5.40 5.43 h Mn(PMT)6(C104)2 white 195-212 5.08 5.30 f Co(PMT)6(CIO4)2 rose 195-205 5.43 5.61 f Zn(PMT)6(C104)2 white 148-150 5.98 5.98 f Fe(PMT)6(C104)2 lt.brown 194d ---------- f Fe(PMT)6(0104)3 lt.brown 196d ---------- f This complex was prepared in DMP (see p. 25). This complex was prepared in nitromethane (see p. 26). This complex was prepared in DMP (see p. 27). This complex was precipitated from acetic acid (see p. 27). This complex was prepared in nitromethane (see p. 28). This complex was prepared in DMP (see p. 29). This complex was recrystallized from CHCl -CCl mixture (see p. 29). This complex was precipitated from water (see p. 34). 31 dawn. meHOHSOHmnM .. + noses 4o?z .. a .4434 403:2 .AMIOH x 4:80 SS 6.490on cognaomne. 46,464.43 .4 0.45me To wd To 6.4 4.4 m4 m4 4.4 m4 o.m Tm o.m 0.4 L F r t . P L a 4.1 h b _ _ O c. a f. r .. a. a a. \, ._ - l. .1 A... \W m.” .1. N; P w )A HRS r; \ . x: . M “a, \ / x c fr... ._ \I.\ W a. .4 > \ C /.\ a.4/ ..\. .r t - 1\ NC.‘ .1. 1 6.8pr 44oo-m4omo act 84438 $438435sz 84 >.o m.o m.o 0.4 4.4 m.4 m.4 4.4 m.4 o.m m.m o.m 0.4 p p a 4 . _ L L p p p L; r O 1.1.} 45.. , a i . i. 1 \m m ‘ n 0 1 .4 l, 1. .__ a. N _. ./ .1 + .. 3 . a... a. 22. , E a .1 ,1. .J. a g a \J/ V 4,. ..\ m. m ._ MW ,7 BR ., :. i, .. e. a. .1 1 ,, as... A l r... z 42/ N .4. ; mm. “M M, M/H \ xxx.» 4., "Mr“ W. C r, .«F /.\ J. . .4 4.333... r a .. v m a. / a? , .. L. 2, l 1 ,2 l , a... 2 xxx / ... (4.. \a. 4....5.\\ L ..¢.\ Wing /(1. E .38 oSooe scam 4.3346488 mA4o4S4Aawmw5 OOH 400.400. mpmhoanohnmm ._. ads-m0- Hogz. .- 4 Add: 46.4.52 .Amnoa x H 08 44.3 0.490QO moan-mama» 004-mafia .m 0.4?me 4.0 .0 0.0 0.4 4.4 .4 m4 .4 m. 0. m. 0. 0. _ ®_ _ _ 1 L.” N _ L +~+ 4. _ N .N .M .d O .0. . .0 .. .4 .4 _ 4. .n 0.. \ f M t. 4 .. .. m _ .. f 41 M m 4 ,3 .._ / 3 4 r.. 4 . _.. P ... .1 ,4 4. r. a}. W .. y ., 9* 0.. L. x 4 x / 4. ac T .0 . .... (2... 4 .3 .3. 0 .4, > x. C ... E m 4 W (x \si .4 a .- . I 1 a m .- 4, 4.. C ”r \m. .4 , .4 (We 34. 4. . a ,... ..... . .32... :25 4 2).... r < .. ..... > \- m N .../. . 22.2..-2. 3... .04.:pr 4400- 4000 50.4.4 0054439202 20483.0?450 00H 50 9.0 “0 044 .4 £4 $42404 2.4 ohm Fm Rm 34 . 4...... 4.. J - o , m. .u r. .\\ 4. w 4 x. \\. r. 4. 4 r.- .H /. 4 ._v 4.. “m “ #M “w“ . x .. r N 0 r 4. .4 4 M x W m .. 4 . . . ... /. "\M \ M “)4. 24‘ * m w . _. x“ m). . x. «C. 4.. 4?.“ (J #m. W m 3.. m -f/ )1 Bfi .2. N .. .3, 4). H/ x). 1\ , 4 C q. 4 ‘ ... 4.. 4......\\ ,. .4 < - . f .0 W 2. . / f w. w. .- r> ..\ K .r..\ m . N . . .3 .- -..-\ 4 . f. - w. 7. K. .020 80.4.4 0334040040 mA4040VmEE050 004 34 Analysis: Calculated: Ni, 5.40%; C, 39.79%; H, 5.57%; N, 30.9#%; C104", 18.28%. Found: Ni, 5.h6%; C. 39.42%; H, 5.70%; N, 30.75%: Clou', 18.52%. Hexakis(PMT)nickel(II) perchlorate was also prepared by adding a twenty molar excess of PMT to an aqueous solution of h. nickel(II) perchlorate. The complex slowly crystallized out 5 of solution over a period of five to ten days. The light blue product (decomposition point 235°C) was identical in all re- spects to that obtained by the DMP method. The infrared b Spectra match rather well as shown in Figure 3 as do their re- spective spectra (Figure 11). Analysis: Calculated: Ni, 5.40%; C. 39.79%; H, 5.57%; N, 30.90%; 0104', 18.28%. Found: Ni, 5.93%; c, 39.67%; H, 5.56%; N, 31.09%; 0104‘, 18.36%. Hexakistentamethylenetetrazole)manganese(II) Perchlorate This complex was prepared exactly like the correSponding hexakisMQ mamnpmsoapwn z m -oa x m.m nH.Empmhm Hzmuomm m.mfl:oaov:o map we mzpmsmao>m3 macflaw> pm h©SPm coflpmflam> msodsflQQOO < .m maswfla w.0 a: P.o wcwwfla so qoflpomam mHoE m.0 .8 1E oww m.o #, so m.o 0.0 IOmO.O :ooa.o fema.o joomd [Omm.o loom.o OWW.O aoueqxosqv #1 .m. -oa a o.m . mo coflpmapQCUQOQ anewphawcm HopOp w mcfl>mn msmnpmaoapflc SH Empmhm 92m:omm w.mA:OHovdo map %0 mflpmcoam>m3 macflam> pm hddpm noflpmflam> macssflpcoo < .m madmflm pswmfla a0 soflpomaa mHoE IOON.O IOOM.O I aousqxosqv :oos.o 100m.o a com :oom.o as one -oca.o 42 43 perchlorate hexahydrate solution in nitromethane a hypsochromic shift with an accompanying hyperchromic effect was noted.‘ The solvated cOpper ion absorption band shifted progressively from 770 mu (molar absorptivity 15) down to 670 mu at a 4:1 PMT to Cu2+ ratio (apparent molar absorptivity 82.5). As the PMT to copper ratio was increased further, the peak started to shift in the Opposite direction. The maximum displacement was obtained at PMT/Cu2+ ratio 40:1 at which point the absorbance maximum was 705 mu with an apparent molar absorptivity of 113 (Figure 7). As additional PMT was added.the maximum did not shift but the absorbance increased. Although the limiting absorbance was not reached, it appeared that the absorbance tends toward a limiting value. This behavior will be reinvestigated. The Hexakis(pentamethylenetetrazole)c0pper(II) Perchlorate The apparent molar absorptivity of a 0.01 m hexakis(PMT)- cOpper(II) perchlorate in nitromethane was 102.3 at 680 le (Figure 8). When additional PMT was added, a bathochromic shift to 705 mu with an accompanying hyperchromic effect was noted, similar to the behavior described above. The Tetrakis(pentamethylenetetrazole)cOpper(II) Perchlorate A 0.01 g solution of tetrakis(PMT)copper(II) perchlorate in nitromethane had an absorbance maximum at 670 mu with an apparent molar absorptivity of 80.2. Upon addition of excess PMT, the peak shifted to a limiting value of 705 mu (apparent molar absorptivity 119) at a 20 mole excess of PMT (Figure 9). Absorbance 1.u0— 1.20“ 1.00“ 0.805 0.605 10 :6 0.80- 5 A O OeLO- ? l O \\\y‘;_.// I l I T i I #00 500 600 700 800 900 wavelength in mu -2 Figure 7. A Spectrophotometric study of 1.0 x 10 M Cu(ClO ) '6 H 0 in nigyomethane upon addition of PMT. The respective PMT/Cu ratio is indicated on each curve. nu. Absorbance l.h0‘ 1.20. O 1.00- :0 l; ’7’ 0.80 O 0.60- L 0.40“ 0.204 I ‘I i I I 1’ ‘ #00 500 600 700 800 900 wavelength in m“ -2 Figure 8. A spectrOphotometric study of 1.0 x 10 M Cu(PMT) (Cth)2 in niEromethane upon addition of PMT. The respective PMT/Cu ratio is indicated on each curve. 45 Absorbance 1.h0 a 1.00 1 0.80 _ 0.60 — 0.h0 ‘ 0.20.— 20 ”l5 10 \V i T? l I I i #00 500 600 700 800 900 wavelength in mu Figure 9. A spectrophotometric study of 1.0 x 10‘2 141 Cu(PMT)h(C10h) in nitromethane upon addition of PMT. The respective PMT/Cu2+ ratio is indicated on each curve. #6 Attempted Determination of the Stepwise Formation Constants by Spectrophotometric Methods From the results obtained by the method of continuous variations (Figures 5.6) it can be assumed, due to the shifting of the maximum, that more than one absorbing Species is present in solution. The method of Newman and Hume (85) was used in an attempt to calculate the successive formation constants (Appendix I). As shown above, however, an accurate limiting molar absorptivity could not be obtained and since this method is based on obtaining a limiting absorbance for the complex, the study was temporarily discontinued. Visible and Reflectance Spectra of the Transition Metal Com- plexes of Pentamethylenetetrazole Visible and Near Infrared Spectra As shown in Figures 10412 and Table II, the visible spectra of the complexes in nitromethane are essentially those expected for the reSpective transition metal ions in octahedral config- urations. The spectra of hexakis(PMT)iron(II) and iron(III) were not run. The spectrum of hexakis(PMT)manganese(II) perchlorate could not be obtained due to its limited solubility and extremely low molar absorptivity (86) while hexakis(PMT)- zinc(II) perchlorate is colorless. Cobalt(II) Perchlorate Hexahydrate and Hexakis(pentamethylene- tetrazole)cobalt(lf) Perchlorate The spectra of cobalt(II) perchlorate hexahydrate and hexakis(PMT)cobalt(II) perchlorate are listed in Figure 10. 47 Absorbance 1.20 1.00 0.80 ‘ 0.60 0.80 wavelength in mu Figure 10. nitromethane. The visible and near infrared spectra of l x 10-2 (solid line, 1 cm cells) and 5 x 26 H2 0 (broken line, 5 cm cells) in 1’1 49 The cobalt(II) perchlorate spectrum shows an unsymmetrical absorption band, due to a shoulder on the high frequency side at 19.800 cm”1 (504 mu) and.has a molar absorptivity of 10 while the hexakis(PMT)cobalt(II) perchlorate spectrum has a somewhat more symmetrical absorption band at 20,600 cm-1 (485 mu) which has an apparent molar absorptivity of approxi- mately 22. These Spectra are typical of high Spin octahedral complexes of cobalt(II) which has three spin-allowed d-d trans- itions from the ground state 4T1(F) to states 4T201), “A2(V2), and “T1(P)(V3) (87). The main band at approximately 4 20,000 cm'1 (500 mu) is due to the T1(F)-uA2 transition (v1), whereas the Shoulder on the higher frequency side is the 4 4T1(F)-uT2 transition (v1) T1(F)-4T1(P) transition (v3). The lies in the near infrared and is probably the weak broad band at approximately 9300 cm"1 (1075 mu) with an apparent molar absorptivity 5 and 8320 cm'1 (1200 mu) having a molar absorp- tivity 2 for hexakis(PMT)coba1t(II) and cobalt(II) perchlorate, respectively. Nickel(II) Perchlorate Hexamydrate and Hexakis(pentamethylene- tetrazole nickel(II) Perchlorate The Spectra of nickel(II) perchlorate hexahydrate and hexakis(PMT)nickel(II) perchlorate are listed in Figure 11. The nickel(II) perchlorate Spectrum shows an absorption band (v1) at 8850 cm'1 (1130 mu) having a molar absorptivity 7.1 and a second broad band (v2) which is split into two bands at Absorbance 1.20: I I I I I I I I 1.00m I I \ I I 0.804 ‘ I I l I 0.60‘ I I II” ‘\‘s } / ‘\__‘\ 1’ I 1’ 0.40. I I \ ’ I I I I I I I I I I I I 400 500 600 700 800 900 1000 1100 wavelength in mu Figure 11 The visible and near infrared spectra of 1 x 10_2 M Ni(PMT) (C10) (solid line, 1 cm.cells) and 6. 72 E M§i(Clgh 3 6 H2 0 (broken line, 10 cm cells) in nitromethane. hTh e spectrum Obtained for Ni(PMT) (C10 ) precipitated from water is identical to éhe soli ine. 50 51 14,070 cm'1 (710 mID and 15,400 cm'1 (650 mID having respective molar absorptivities of 6.4 and 7.0. The lower frequency edge of v3 appears at 25,000 cm'"1 (400 mp),but v3 cannot be determined due to solvent cut-off at approximately 25,000 cm‘1 (10 cm. cells). The hexakis(PMT)nickel(II) perchlorate Spectrum in nitromethane consists of only two absorption bands v1 at 10,500 cm.1 (950 mp) and v2 at 17,400 cm'1 (575 mu) having reSpective molar absorptivities of 8.0 and 9.5. These spectra are characteristic of the Spectra obtained for octahedrally coordi- ynated complexes which have three Spin-allowed d-d transitions from the ground state 3A2(F) to states 3T2(v1), 3Tl(v2) and 3T1(P)(v3). Thev2 band of the nickel(II) perchlorate spectrum is split into two bands as a result of the Spin-orbit coupling mixing the 3T2(F) and 1Eg states which are very close in energy (88). The Shifted v1 and v2 bands to higher energies indicate that the nickel(II) ion is in a stronger ligand field in hexakis(PMT)nickel(II) perchlorate complex than in nickel(II) perchlorate hexahydrate. As a result of the stronger ligand field, the 3T2(F) and 1Eg state move farther apart which accounts for the lack of splitting of the v2 band in hexakis(PMT)nickel(II) perchlorate. Capper(II)_§grchlorate Hexahydrate Tetrakis and Hexakis- (pentamethylenetetrazolefcopper(_l Perchlorate The spectra of copper(II) perchlorate hexahydrate, tetra- kis and hexakis(PMT)c0pper(II) perchlorate (Figure 12) all Absorbance 1.20— 1.00'1 "\ 0.80'4 If, \ I ‘\ \ 0.60-l \\ \\ \ 0.u0- \\ \\\\ \\\\ \. 0.20- , \\\‘~ /’ ~~s-~~ \ 1”, -..~_“ 's \ / "“\‘\\4 \\\ ar” ‘-"‘"‘ -—:———e—” I *r* ”I I I I l I 400 500 600 700 800 900 1000 1100 wavelength in mi Figure 12 The visible and near infrared spectra of l X 10.2 M Cu(PMT)6 (ClO ) (solid line), Cu(PMT;h(ClO:2 m) (short- long-short brogen line), and Cu(ClO 0 (broken line) in nitromethane using 1 cm ce ls. 52 Table II ElectronigyAbsorption Spectra (in cm'{)of the Transition Metal Complexes of Pentamethylenetetrazole :— f- Complex State W~max. (e Molar for Solution) Co(C104)2'6 320 solnb 19,800 (~10), 9.310 (:5) Co(PMT)6(C104)2 solnc 20,600 (~22), ~8,300 (~5) Co(PMT)6(0104)2 solid 20,400, 8,500 Ni(C104)2~6 320 solnd 15,400 (7.0). 14,070 (6.4), ?,85? 7.1 Ni(PMT)6(Clou)2 solnc 17,400 (9.5). 10,500 (8.0) Ni(PMT)6(0104)2 solid 26,300. 16,000, 9,760 Ni(PMT)6(C104)Za so1n° 17,400 (9.5), 10,500 (8.0) Ni(PMT)6(CloL,)2a solid 26,300, 16.000, 9.760 Cu(ClOu)2°6 320 solnc 12,900 (14.7) Cu(PMT)6(C104)2 so1n° 14,530 (103) Cu(PMT)6(C104)2 solid 13,500 . Cu(PMT)4(ClOu)2° soln° 14,920 (81) Cu(PMT)u(C104)Ze solid 16,000 Fc(FMT)6(0104)2 solid 10,000 a. This complex was precipitated from water (see p.54 ) b. 5.0 x 10'3 M.in purified nitromethane - 5 cm cells c. 1.0 x 10‘2 ‘M in purified nitromethane - 1 cm cells d. 6.72 x 10'3 M’in purified nitromethane - 10 cm cells c. This complex was precipitated from acetic acid (see p. 27) 53 54 Show a Single broad band at approximately 12,900 cm"1 (775 mp), 14,920 cm'1 (670 mIO, and 14,530 cm"1 (687 mu) having reSpective molar absorptivities of approximately 15, 82, and 113. These spectra are typical of cOpper(II) complexes which theoretically have only one allowed transition (ZEg-2T2(D)). Hewever, this band is probably made up of two or three overlapping symmetrical bands Since the tetragonal distortion, usually associated with copper(II) ions, Splits the E8 and T28 levels so that more than one d-d transition is possible (89). Reflectance Spectra The absorption maxima found by reflectance measurements were essentially the same as those found in nitromethane solution (Figures 13-15). Absorption bands arising from PMT l in the appear at approximately 8160, 7030, 5720 and 5200 cm- reflectance spectra of the reSpective complexes and are not listed in Table II. Thermogravimetric Studies of the Transition Metal Complexes of Pentamethylenetetrazole The thermogravimetric analyses were carried out in a nitrogen atmoSphere with a heating rate of approximately 2°C per minute. Tetrakis(pentamethylenetetrazole)c0pper(II) Perchlorate The decomposition of tetrakiS(PMT)copper(II) perchlorate began at approximately 126°C. The rate of the reaction was .Acana scxosov mAsowoverzmvoo was ACSHH UHHOmV NAzoaonAezmvmm ac mhpommm monopomawma one .mH maswwm owom owma 4.8 Ca mesmam>s3 OOOH 00m _ 55 .Hmpmz Sosa Umpmpamflomag NAJOHovaBvaHZ was “mafia wflaomv mam Sosa Umpmpflmflooaa mAaoaovaBzmvflz mo caveman megapomaama one .dH madmflm .18 SH npmcmam>s3 Gowm coma OOOH 00m . F 56 . Ans: access; mflsoaovsgmvoo was ACSHH wflaomv mAdoaovaEzmvso mo wepocmm monopomaama 0:9 .mH masmflm 18 CH mesoama/mz £00m OOmH OOOH 00m _ a . 57 58 slow until the temperature reached 180°C at which point the weight loss was 4%, beyond this point the reaction rate in- creased abruptly. The reaction was strongly exothermic, as in- dicated by the bulge in the volatilization curve. The sample then decomposed violently, and the momentum imparted to the sample holder broke the quartz spring from which the sample holder was suSpended. As a result, the values recorded above that temperature are meaningless. Evidently this material Should be handled with caution (Figure 16). Hexakis(pentamethylenetetrazole)cOpper(II),Perchlorate The decomposition of Cu(PMT)6(ClOQ)2 commenced at approxi- mately 165°C. The rate of the reaction increased rapidly, and at 180°C the rate of volatilization reached explosive limits and the momentum imparted to the sample holder carried it past the point of 100% weight loss. The reaction was exothermic, Judging by the increase in temperature at the end of the decom- position of the sample (Figure 16). Hexakis(pentamethylenetetrazole)manganese(II) Perchlorate The sample Showed a small decrease in weight starting at approximately 30°C. At 150°C the weight decrease was 1.3%. This loss may be due to a small amount of residual solvent or other volatile material. Beyond 150°C the complex began to decompose and the rate of decomposition increased Slowly with increasing temperature. At a weight loss of 30%, which Ecrcent weight loss 1001 Figure 16. I r 100 200 500 400 Temperature °C The thermogravimetric analysis of Cu(PMT)h(010h)2 (solid line), Cu(PMT) (Clou)2 (short-long-short broken line), and Mn(PMT) (010 ) . . . 6 4 2 (broken line) in a nltrogen atmosphere with a heating rate of approximately 2°C per minute. 59 60 occurred at approximately 222°C, the decomposition of the material became increasingly endothermic. Between weight loss values of 42% and 48% an endothermic effect was evident reaching a maximum at a weight loss of 45.1%. The volatilization con- tinued at a decreasing rate until, at approximately 390°C, a residue of 23.2% remained which correSponds to Mn(0104)2. At this temperature the rate was increasing, and further loss probably would have occurred if the run had been continued to higher temperatures (Figure 16). Magnetic Susceptibility of the Transition Metal omplexes of Pentamethy_enetetrazole The magnetic susceptibilities of the transition metal com- plexes of PMT were determined by the Gouy method. The Gouy susceptibility tube used in this study was constructed from 6 mm I.D. Pyrex tubing. The distance from the reference mark to the septum of the tube was 6.5 cm. The volume of the tube was determined by measuring the weight of distilled water (1.893 grams) needed to fill the tube to the reference mark. The volume was calculated by dividing the weight of water needed by the density of water at the ambient tempera- ture of 23.30C. The volume of the tube was calculated to be 1.898 ml. The respective PMT complexes were then ground to the con- sistency of fine powder. The Gouy susceptibility tube was packed by placing a small quantity of the powdered sample in the 61 tube and tapping it firmly on a stone surface sixty times. This process was repeated until the tube was filled to the calibration mark. This method was employed to minimize the errors resulting from a lack of uniform packing which, in general, is the main limitation on the accuracy of the determination. This Gouy susceptibility tube was attached by a c0pper wire to the pan of a Mettler single-pan balance and sus- pended between the pole faces of an Alpha Scientific Labora- tories model AL 7500M electromagnet. .All changes in weight reported here are the averages of three successive readings on the same sample. Mercury(II) tetrathiocynatocobaltate(II) was used as the apparatus calibrant. Figgis and Nyholm (90) report a gram susceptibility for this compound of 16.44 (1_0.05%) x 10"6 at 20°C and that it obeys the Curie-Weiss law between 10 and 30°C. The magnetic susceptibility of the complexes in Bohr magnetons, and the number of unpaired electrons in these complexes were calculated by the following method. The gram susceptibility Xg can be calculated from the relationship 2 i—AH;=C (l) IDXS 2 62 where: AH2 —E— = Apparatus constant = c in grams IAN = Change in weight in grams of the calibrant in and out of the magnetic field A = Cross-sectional area of Gouy tube in cm2 :1: ll Strength of the magnetic field in gauss Density of the calibrant in grams/cm3 '0 II X8 = Grgm susceptibility of the calibrant in cm /gram Volume susceptibility X can now be obtained from the equation: and the molar susceptibility, XM then calculated by multiplying volume susceptibility by the molecular weight of the sample, MW xM = 1:wa5 (3) p The number of unpaired electrons were calculated from the following relationships: 2 2 x =NBB (4) M ‘3JkT' where: N = Avogadro's number 20 B = 0.917 x 10- erg-gauss"1 (is = Magnetic moment k = Boltzmann's constant T = Absolute temperature and us =[n(n+2)I% (5) 63 where: n = number of unpaired electrons in the unfilled shell. Substitution of equation 5 into equation 4 and solving for n, yields the following expression for the number of unpaired electrons; I n =[-1 1_ 1+(2.420 x 103)(XM)]% (6) The respective magnetic moment in Bohr magnetons can also be calculated from equation 4 and is given by the equation. .15: (2.4243 x 103 ° XM)%: erg gauss'l (7) The experimental magnetic susceptibility data for the respective complexes are listed in Table III. The calculated values for the magnetic moments in Bohr magnetons and the number of unpaired Spins are listed in Table IV. All measurements were taken at an ambient temperature of 296.5°K. Calculation of Ma etic Susce tibilit of Hexakis(penta- methylenetetramoIeIcOpper(II) Perchlorate Using the data given in Table III the molar susceptibility was calculated in the following manner: XM = egg! 1 ' 0000313 1321,48 = 1.6641 x 10'“ cm3 mole-1 The experimental molar susceptibility was a negative number indicating diamagnetism. Therefore, diamagnetic correction values for PMT, perchlorate anion, and the central metal cations were incorporated in the following manner: 64 xM (Corr.) = xM (obs.) + aXM(PMT) + bXM(CIOu_) + oxM (metal) The calculated XM (obs.) can be a positive or negative value while the three correction susceptibilities are taken as positive values. The correction coefficients of the sus- ceptibilities are the reSpective moles of each chemical species contained in the complex. Table V gives these molar diamagnetic susceptibilities. XM (corr.) = (-1.6641 x 10'“) + (6)(2.22 x 10-“) + (2)(0.32 x 10’”) + (1)(0.128 x 10'“) MM (corr.) = 12.42 x 10'“ cm3 mole-1 The number of unpaired electrons in the complex is calcu- lated by substituting XM (corr.) into equation 6. n -l 1,[l+(2.420 x 103)(12.42 x 10‘“)]% n -1 + (4.01)% = 1.00 unpaired electrons The experimental magnetic moment in Bohr magnetons of the complex is calculated using equation 7 and the corrected value of molar susceptibility. 08 [(2.4243 x 103)(12.42 x io‘“)I% PB 1.74 B.M. X-Bay Powder Diffraction Studies of the Transition Metal Complexes of Pentamethylenetetrazole All the X-ray powder pattern photographs were obtained using a North American Philips Company, type 12045, X-ray generator and a type 52056, 114.6 mm. camera. Ilford brand .musmEmHSmmmE Ham How usmumcoo was: cam macaw mmnm mm Cu pmumfisofiwo mm3 usmuwcoo maumumaam 65H .Mom.om~ mo musumumafimu ucmwnfim um um cmeu mucmamusmmmfi HH< .HE mowmw.H u oEDHo> onsH m.w New0m.am u uLmeB snap xuaEm . mEsHo> on:u\AuLwH63 snap xuaso I mmo pamflm .uBVw 65 Qamms.o macoo.o- mmsm1.mm Naoma.mm emsa.wma Baa mmmmm.o mNmoo.o- Nmssm.mm m~¢sm.~m ssmm.ame soHomAaszSU Naomm.o mamoo.o- oasac.mm saaao.mm oaam.maoH NAsoHochHzach seams.o oNsHo.o maoom.mm mmmwm.wm Namm.mwaa mAeoHochezmvca snoom.o moNoo.o- mHsNN.Nm mammm.mm mma.maw mascaovefiezavso amass.o semoo.o asmmc.mm mmasc.mm camc.cwoa «AsoHovoAazavaz somas.o maamo.o massc.mm Hmooo.mm wssw.owoa mascaovcaazavoo mcaws.o osamo.o Namwm.mm Nmmmm.mm seam.mon NasoHovoAHZavsz oNomm.o Nowao.o aamsm.~m madam.mm owes.mwoa NAs0aochesavca maomc.o mmooo.o- mesoa.~m memoa.wm cams.aa0a mascaovoaezavao amasso mac cases so cases 3: AHE\mEmuwv Amfimuwv AmEmuwv Amfimumv uswfioz sauwmsma uswaS uswwmz uswwo3 umHsuwHoS xmaaaou odoumuuouosofiwmwmfimucmm mo moonmEou anus: cowuwmsmufi ozu mo mumn zuwAHnfluaoomsm owumcwmz HHH mqmH mqm 9.0 10.0 T Cu(PMT)20101+ in Pyridine TMS r l 'l I T T 5.0 6.0 7.0 8.0 9.0 10.0 T Figure 17. NMR absorption spectra. Tetramethylsilane was used as the internal standard. 81 82 Tetrakis and Hexakis(pentamethylenetetrazole) Transition Metal Perchlorate Complexes All of the metal complexes of PMT prepared are paramagnetic with the exception of hexakis(PMT)zinc(II) and bis(PMT)- copper(I) perchlorate which are diamagnetic and yield pre- dicted NMR Spectra. The NMR spectra of hexakis(PMT)- manganese(II), iron(II), iron(III), cobalt(II), nickel(II), copper(II) and tetrakis(PMT)copper(II) perchlorate were run and no absorbances were detected within the entire sweep width of the Varian A-60 Proton SpectrOphotometer (-1000 to 2000 CPS). Since paramagnetic ions have been responsible for large shifts of proton absorbances (96), one possible explanation for the lack of the predicted NMR Spectra is that the absorbances are shifted beyond the sweep width limits of the instrument. Infrared Absorption Studies of the Transition Metal Complexes of Pentamethylenetetrazole (5000— 680 cm'IfregiomI Infrared Spectra were obtained for PMT and for all the complexes prepared in this study (Figures 18-27 and Table XII). All the Spectra of the complexes were obtained in Nujol mulls while PMT was obtained both in mull and in a pressed KBr pellet. The bands arising from Nujol appear at approximately 2940(s), 1460(S), 1381(S), 1100(w), and 83 725(w) cm"1 and are not listed in Table XII. Potassium bromide pellets were not used due to the suSpected forma- tion of the corresponding transition metal bromide-PMT mixed complexes. When the hexakis(PMT)cobalt(II) and c0pper(II) perchlorate complexes were pressed at approxi- mately 8 tons pressure, the resulting disks were blue and green respectively. Gill, gp_gl. (97) reported the same colors for the tetrahedrally coordinated complexes of bis- (pyridine)cobalt(II) and copper(II) bromide. Each sample was mulled by weighing 100 milligrams of the complex and 200 milligrams of Nujol into a plastic mulling capsule containing a plastic ball. The capsule was rapidly agitated for two minutes using a Wig-L-Bug (Cresent Dental Mfg. Co.). The mulled sample was then transferred to a sodium chloride plate and inserted into the instrument. The infrared Spectra were interpreted relative to the Spectrum of PMT and the literature values for the various perchlorate bands. No attempts were made in this study to assign the bands of PMT or any of the complexes prepared. Hexakis(pentamethylenetetrazole) Transition Metal Per- EhIorateS Comparison of the Spectra of PMT (Figure 18) with those of the hexakis(PMT) transition metal perchlorates (Figures 19-25) Show little change in the PMT spectrum upon TABLE XII Infrared Absorption Bands (in cm-l) of Transition Metal Complexes of Pentamethylenetetrazole (Nujol Mulls) PMT Mn(PMT)6(ClO4)2 Fe(PMT)6(C104)2 a b a b ---------- 34458 ----- ---—- -------------------- 3370m ---------- 1700w ---—- 1700w ---------- 1640m ----- 1625w 1530m 1530m 1540m 1532m 1535m ----- 1348w 1346w 1348w 1348sh 1319w 13353h 1338sh 134OSh 13353h 13103h 1313w 1315w 1314w 1315w 1272w 1292w 1293w 1295w 1295w ----- 1259w 1260w 1259w 1260w 1248m 12423h 12423h ----- 124OSh 1190w 1188w 1190sh 1189w 1189sh 1174w 117OSh ----- 117lsh ----- 1118m -------------------- 1099w -------------------- ----- 'VI091vs 'Vl090vs 'VI098vs 'Vl090vs 1090w -------------------- 1079w -------------------- ----- 1029w 1032w 1028w 10303h 994m 1008m 1008m 1008m 1007w 964m 964m 968m 968m 969m ---------- 920w ----- 932w ----- 8988h ----- —---- 9OOSh 895m 892m 893m 882m 892m 864m 868m 868m 868m 868m 833w 831m 832m 832w 831m 798m 801m 801m 801m 802m 743w 746m 746m 747m 746m 719w 721m 721w 722m 722w 675m 677m 676m 678m 677m ---------- 668Sh ----- 699sh 631m 6323h 632$h 633Sh 632$h This complex was prepared in DMP with an 8:1 ratio of PMT to transition metal perchlorate (see p. 29). This complex was prepared in DMP with a 4:1 ratio of PMT to transition metal perchlorate (see p. 37). 84 TABLE XII (continued) C. Fe(PMT)6(C104)3 Ni(PMT)6(ClO4)2 a b a c b -------------------- 34005 -------------------- 1690w -------------------- 1645w 1598w -------------- - ----- 1530m 1535m 1520m 1532m 1535m 1345w 1348w 13503h 13503h l348w 13353h 13353h 13353h 13383h 13353h 1312w 1315w 1312w 1313w 1318w 1293w 1296w 1295w 1295w 1299w 1260w 1260w 1260w 1260w 1260w 124OSh 12453h 124OSh 124OSh 12483h 1187w 1192w ---------- 11983h 117lsh ll74w 117OSh ll7OSh ----- 1082vs ~1090vs ~1092vs ~1088vs ~1090vs 10285h 1030w 1029w 1029w 10303h 1005w 1010m 1012m 1011m 1012w 966m 968m 967m 966m 968m -------------------- 930w ----- 9OOSh 898sh 898$h ----- 892m 893m 891m 890m 894m 866m 868m 868m 867m 869m 831w 833m 832w 831w 832w 801m 803m 802m 802m 803m 744m 747m 747m 746m 746m 722w 722w 719w 722w 722w 676m 677m 677m 677m 679m 6683h 67OSh ----- 668sh 669sh 85 This complex was precipitated from aqueous solution (see p. 34). TABLE XII (continued) Co(PMT)6(C104)2 Zn(PMT)6(C104)2 Cu(PMT)6(C104)2 a b a b a ----- 34603 ----- 3480w ----- ----- 1710w ----- ----- ----- ----- 1640m ---—- 1635w ----- 1532m 1535m 1530m 1535m 1530m 1345w 1352w 1344w 13503h 13503h 13355h 1336sh 1335w l337sh 13385h 1312w 1318w 1313w 1317w 1317w 1293w 1295w 1292w 1296w 1298Sh 1260w 1263w 1258w 1261w 1358w 124OSh 1244sh 1240w 1243sh 124OSh 1189w ----- 1190w 1190w 1193Sh ll7lw ----- 1173w 1174w 1172w ~1087vs ~1090vs ~1080vs ~1094vs ~1089vs 1026w 10323h 1029w 1030w 1028w 1006m 1009m 1010m 1010m 1010m 965m 970m 965m 670m 967m ----- 932w ----- ----- ----- 896sh 9OOSh 8985h 899sh 904w 891m 892m 890m 892m 892m 867m 869m 867m 869m 868m 832m 833m 830m 832w 832m 801m 803m 800m 802m 802m 746m 748m 747m 746m 744m 722m 722w 721m 722m 721w 677m 678m 678m 677m 678m ----- 668sh 67OSh 668$h ----— 633sh ----- 6323h ---------- 86 TABLE XII (continued) d b e f g --------------- 3615w 3630w ----- 3500w 3495w ----- ----- 1680w -------------------- ---------- 1625w —---- 1640w ----- 16053h 1570w 1615w ----- 1540m 154OSh 1540m 1540m 1540m 1341w 1342w 1348w 1346sh 13483h 1322w ----- 1325w ---------- 1305m 1305w 1308w 1303w 1303w 1267m 1268m 1270w 1268w 1268w 12423h 1247sh lZSOsh 1249sh 1249sh 1205w 1203w 1209w 1204w 1204w --------------- 1142m 1139m ~ 1091vs ~ 1087vs ~ 1095vs ~ 1088vs ~ 1090vs IOZOSh 102OSh lOZOsh ---------- --------------- 972m 972m 969m 968m 973m 964sh 964sh 924w 925$h 926w ---------- 896m 897m 900m 899w 899w 867m 868m 870m 868w 868w 835$h ----- 840w 839w 839w 801m 800m 802m 805w 805w 743m 741m 744m 738w 738w 721w 722m 722m 722w 720w 674m 673m 677m 679w 678w 664sh 669sh 659w ---------- 633sh 6353b 636sh 6353h 6353b d. This complex was precipitated from anhydrous acetic acid (see p. 27). s. This complex was precipitated from nitromethane (see p. 28). f. This complex was prepared in nitromethane (see p. 26). g. This complex was precipitated from DMP (see p. 25). 87 means Hones - 4 .92m mo AMIGA x Hiao Gav wapommm SOHPQHOmQ< emanamaH .wH maswflm >0 0.0 0.0 04 HA mam m4 114 m4 0.m Tm 0.m 0.: p P L. L - L . _ r _ _ . . p a as Honsz -ezm e0 00 0.0 04 #4 m4 m4 :4 m4 0.m Tm 0.m 0.: k _ _ v _ _ _ . _ _ _ _ _ pmaaoa ooflsoap.efiflmm090m I 92m 88 damn mpmaoanoamm I + means acmsz I .Hasfi acnsz .AMIOH x a E0 SHV mapommm noflpmaomn< emanamcH .mH maswflm e.0 0.0 0.0 0.H H.H m.H n.H s.H m.H 0.m m.m 0.m 0.: a . am. In a a a w.III p a p 4 .. l a .1 man an eosucs cases a": - mfisoaovmflazmvsz emo 9.0 who 0MH HMH m.m m.m s.m mafi . 0mm mam own 0“: + 4 a man as scenes oases Hum I mfls0aovmfiezmvsz 89 wasp mumaoaaoaom I + mesmp acndz I a .HHSE acndz .AMIOH x HIEo SHV mapommm coflpmaomn< UmamaasH .om mhsmflm v.0 w.o m.o o.H H.H N.H m.H :.H m.a o.m m.m o.m 0.: — _ _ F — , _—_ _ — p p + a 4 4 man an access canes H": I masoflovmfiazmvca w.o m.o o.H H.H N.H M.H :.H m.H o.m m.m o.m 0.: _ r _ _ _ .b. _ _ P _ + a. . a,m as scenes oases Ham I mAsoaovmneamvca 90 damp, opmaoasoaom I ._. 3:00. Henna I a 1358 acnsz .AMIOH x HIEo S3 0.3.0on soflpmaomna. cmHmHEHH .Hm warm 0.0 0.0 0.0 0;” HA NA n4 :4 m.._.. 0.m m.m o.m 0.: m . _ P h r p — p - — - _ . 1 4 man an eosacs cases 4.: I mas0aovmfiazmvca W40 No 0.0 04H HLH ImsamH:m ma 04m new can 0.: 9 ._. 4 w mam as scenes oases Hum - masoaovmfiasmvca 0900. opmaoaaoamm I + 00:00. H0052 I a .358 acnsz .AMIOH x HIao 5V mapoomm soapmaomoa. 00.803 .mm 930$ v.0 % o 0.40 0:” NA mm mu” :1 m_._u 0..m mm 0.0 0._: A. mam as soapcs cases a": I NA:0H000Aazmvaz 92 >.0 0.0 0.0 0.H H.H mha 0ma :MH mas 0.m mam p.n 0.: r w p p . on access capes Ham I NA 0H000Aasmvaz 0s09 mpwaoanoamm I + 00s09 Howsz I 4 .4488 4onsz .AmI04 x 80 SHV wapommm SOHpQHOmQ< 004040SH .mm 04504h HI 0.0 0.0 0.0 0.4 4.4 0.4 0.4 :.4 0.4 0.0 0.0 0.0 0.: a . _ 4 41 _ _ 4 _ I4. _ . . l + 14 020 s4 scenes o4psa 4": I 0A:04000Aazmvo0 4.0 0.0 0.0 0.4 4.4 0.4 0.4 :.4 0.4 0.0 0.0 0.0 0.: P r _ L L p — F p p r — p + a a 020 04 eosaes 0406a 4H0 I 04:04000Aesmvo0 93 0smn 0pwaoanoamm I + 00:09 acnsz I 4 .HHSE 400:2 .AmIOH x _E0 SHV 0490040 s04pm4009< 00awamsH .:m 04504m HI 0.0 0.0 0.0 0.4 4.4 0.4 0.4 :.4 0.4 0.0 0.0 0.0 0.: _ _ _ r 4 P F _ p — P h _ c. A A. .420 5 eospes 046.04 4": I 02040003500 40 0.0 0.0 0.4 4.4 0.4 0.4 :.4 0.4 0.0 0.0 0.0 0.: _ _ . h . h . _ _ _ 4 4 a a b. .. .. _ .. 1 mzm S4 0onp0a 04404 Hum I mA:040VmABzmsz IIIIIIIIIIIIK 94 eons 04040406404 I + means 4onsz I a .0420 H0052 .AmIOH x .7400 SS 0.50090 004944400004 00.4.0.4.HSH .mm 0,304.44 N30 ®.O m.o I 01m Him N.H min :.H min O.N m.m O.m or: . L r _ _ _ u _ L _ . _ _ O . 020 04 cospwe o4uca 4": I 0A:0400:A420050 0.0 0.0 0.0 0.4 4AM, 044 mn4 :“4 0M4 0.0 0m0 040 0.: — P — — 4 a 020 04 0o4408 o4pca 410 I 0A:04000A020080 95 96 complexation. There are small (13 cm‘l) absorption shifts which vary with the central metal ion. waever, little information with regard to complexation could be obtained from these spectra. Some evidence concerning the nature of the coordina- tion of the central metal ion can be obtained from the perchlorate absorptions. The perchlorate ion has a regular tetrahedral structure and belongs to the point group Td, having nine vibrational degrees of freedom dis- tributed between four normal modes of vibration. These normal modes are: the symmetric stretch v1 which is theoretically infrared inactive and usually appears as a very weak band at 932 cm'1 due to the distortion of the ion in the crystal field (83): the symmetric bend v2 which is infrared inactive and is assigned a frequency of 460 cm‘1 from the Baman spectra; the asymmetric stretchmi3 l in the infrared which appears at approximately 1100 cm" spectra of ionic perchlorate as a very broad, strong band with a poorly defined maximum; and the asymmetric bending mode'V4 at 620 cm"1 which is beyond the range of the Beckman IRS and is discussed in the far infrared section of this study. If. in the process of complexation. the perchlorate group changes from an ionic to a perchlorato group, the oxygen atom involved in the partial covalent bonding with 97 the central metal ion is no longer equivalent to the other three oxygen atoms, and the symmetry of the perchlorate group is lowered to C3v' As a result, the broad degen- erate v3 band present in the spectra of the ionic per- chlorates splits into two well-defined bands with maxima between 1200 and 1000 cm"1 and the chlorine coordinated {5 oxygen (Cl——o*) stretching frequency‘v2 increases in in- E tensity and appears as a medium or strong band at about 950-925 cm'1 (98.99). Inspection of the Spectra shows that. in all cases, i the broad degenerate v3 band at approximately 1090 cm"1 is not split and the v1 symmetric stretching frequency. when it appears, is very weak. This suggests that the perchlorate group in these complexes is ionic and it appears that the PMT ligands are arranged octahedrally around the central metal ion and prevent coordination by the perchlorate group (83). Tetrakis(pentamethylenetetrazole)copperLIll Perchlorate Comparison of the Spectra of PMT (Figure 18) with those of tetrakis(PMT)copper(II) perchlorate (Figures 25,26), prepared by different methods, shows good correspondence of the various bands. Again little information is obtain- able from the slight shifts of the bands of PMT on coordi- nation. The perchlorate v3 asymmetric stretch is again damn mpwHOHSQHQH I + mwcmp acnflz Ia .HHZE HOnSZ .AMIOH x Eu Gav mapommm coflpmHOmnfi dmawa%sH .mm maswfim HI m.o m.o o.H H.H m.a m.a :.H m.H o.m m.m o.m 0.: _ r r _ . _ a _ _ . r r l + v Noammo ea eeeemeem I mflsoaovsaazmvso w.o m.o o.H H.H m.H n.H :.H m.H o.m m.m o.m 0.: \P r r _ a . _ _ _ a . .I + *__J ml e.o m.o m.o o.H H.H m.H m.H :.H m.H o.m m.m o.m 0.: _ _ _ _ IIL _ _ p . _ _ _ r + CT amass p02 can mozmmo scam omhwmmam I :OHONAHEMVSO N.o ®.O m.o O.H H.H N.H M.H :.H m.H O.N m.m O.m 0.: _ . _ p a r . p . a . _ a . a ago as eczema capes Hum I :oaomAezmvsu 1100 Far Infrared Studies of the Transition Metal Complexes of Pentamethylenetetrazole (680-180 cm"1 regioni A Perkin-Elmer model 301 far infrared double beam spectrometer was used to obtain all of the far infrared Spectra. All the spectra were obtained with the complexes dispersed in NuJol which is nearly ideal for use in the cesium bromide (700-320 cm-l) and polyethylene (320-100 cm'l) regions because it has only one weak band at 725 cm"1 (100). The samples were prepared by the same techniques ex- plained in the infrared studies section (see p. 83). Selected mulled samples were allowed to age for 2h hours and showed no change in absorption in the 320-170 cm'1 region. It was, therefore, assumed that the mulled com- plexes would be stable for the time required to run the sample (about six hours). The spectra in the cesium bromide and polyethylene regions were obtained by use of air and polyethylene of the same thickness as references. Since water vapor absorbs strongly below 320 cm'1 (101),the entire system was con- tinually flushed with dry nitrogen. In order to obtain a spectrum of a complex from 700- 100 cm'1,it was necessary to change gratings, mirrors, choppers and reststrahlen filters several times. It was found convenient to obtain the spectra of all the complexes 101 102 in one region before modifying the instrument for the next region. For this reason the relative intensities of bands for the same complex in different regions probably do not have any significance. The breaks in the Spectra due to these changes are Shown on the figures by interruptions in the traces. Pentamethylenetetrazole The far infrared Spectrum of PMT shows nine absorption bands in the 700-100 cm‘1 Spectral region (Table XIII. Figure 28). All the bands, except the one at 670 cm'l, are probably due to the pentamethylene ring since they are absent in the Spectra of l and S-methyl, 5-ethyl, 5-27 propyl and S-Erpentyl tetrazole (Figures 28-30). The ab- sorption bands in the 500 cm"1 region for the 5-ethyl. 5- grprOpyl and S-nrpentyl tetrazole probably result from.the rocking vibration of the alkyl groups. Anhydrous Sodium and Silver Perchlorate These compounds Show a strong band due to the perchlorate ion in the vicinity of 620 cm'1 (Figure 31). This value agrees with the literature value of 620-630 cm"1 (100). figxakis-(Pentamethylenetetrazole)-TranSition Metal Complexes When PMT is complexed with the transition metal perchlorates, three new bands appear in the far infrared Spectrum of PMT IIIII.‘ l mam HNN saw was -II Nam ohm New mew amm cam Ham mam new III mom saw oaN mam new mmm osm amm amm amm can Nam mom mom mmm mam can mam sam can see see ass Hes ass mas aae mas ass mas owe owe oNo owe III so was so awe so awe so awe awe has mas see see was NAsoHovoAazavaz NAsOHUVoAHzaVoo mascaovoaazavoa NAsOSUVerzavez ass ofioumuuouoconSuoEmusom mo moonmEou Home: cowufimcmua mo AH 80 :HV muuooam commumcH “mm HHHx mqmHpm>HSo© wcoommv mQOBVmEEoN o mfisoaovmfizmvos SH no ssspooam mmm one .wm mama 'H AI Om . . l i. f .. ,1 k A” i w a, .. _.., L. __ I i. a n . i. i M m. l i A. , . z. 1 ~ w m _. _ l x i” .. i W . M .2 a a.” m MM # x .1 11 r M..“. l... s m, a T .1 m WW g .n .2 l. _ w w m r M i.“ l « 151 152 negativity of the two atoms in the bond) gives an extra- polated value at 100% ionicity in good agreement with the theoretical value (137). Forbidden Mn(II) transitions were observed in the spectra of Zn(PMT)6(Clou)2. The transitions consisted of a pair of lines separated by 23.1 gauss from each other between each pair of allowed lines. The relative in- tensity compared to the allowed lines was 1 to 18. The transitions were not observed in either the room tempera- ture or the frozen Spectra of Mn(PMT)6(Clon)2 in the solvents CH3N02, CH3CN, and dimethylsulfoxide (DMSO). From the intensity ratio- 1/18, an approximate value of the measure of departure from octahedral symmetry D. (assuming that the distortion gives an effective axial symmetrya. D can be obtained by the following equation (140,141): 2 D ]' [1+S(S+l) ][I(I+1)-m2+m] - EL 3 I.R. (intensity ratio)- 15[:4'g§§ “FMTH:IT 8This assumption that the distortion is axial is made purely for convenience so that an approximation of the D value can be obtained. sci! 153 where S = 3 (total electron Spin), I = % (total nuclear Spin), m = % (component of electron Spin), and M = % (component of nuclear Spin). From this equation D is 4 cm'l. This value determined to be approximately 750 x 10- indicates that there is a large distortion from octahedral symmetry in the solids since Mn(II) complexes with small distortions have D values in the range of 0 to 200 x 10'“ cm'l. The line width (peak to peak width on the derivative curve) is approximately 10 gauss in Zn(PMT)6(Clou)2 and Fe(PMT)6(ClOu)2. This puts an upper limit on the nitrogen Splitting of approximately two gauss assuming that there are six equivalent nitrogens bonded to the Mn(II). A two 2 equal to gauss nitrogen splitting would give a value of N 0.94 calculated from the equations of Helmholz (142) assuming an sp3 hybrid nitrogen orbital. Part of the explanation for the high ionic character of the metal-ligand bonds may be that it is due to a steric effect. This explanation draws support from the ESR Spectra of Mn(PMT)6(Clou)2 in organic solvents. The absence of the forbidden transitions indicates that the symmetry is octahedral while the ESR Mn(II) hyperfine splitting value indicates that the bonds are more ionic, A = 87.1 in the solution. than in the solid, A = 84.4. 154 This increase in ionicity is consistent with a model in which, after the distortion introduced by crystal packing is removed by dissolving the complex in a solution. the six now equivalent ligands are sterically forced to form more ionic bonds to the Mn(II) than the original inequiva— lent ligands. Tetrakis- and Hexakis-(Pentamethylenetetrazole)Copper(II) Perchlorate. The BBB data are given in Table XV along with some litera- ture data for comparison. A surprising result of this investigation is that it was possible to resolve the copper nuclear hyperfine Splittings in the undiluted samples (see Figure 39). As discussed by Assour and Harrison (143), interactions between neighboring ions are expected to broaden the hyperfine lines so that at best only a reso- lution of the parallel (gll) and perpendicular (g1) absorptions are expected. The present work appears to be the first reported case of high resolution of this type. The corresponding Mn(II) complexes did not Show thiS‘ resolution,presumably due to the greater dipolar inter- action of five unpaired electrons in Mn(II) compared to the one unpaired electron in Cu(II). The ESR data indicate that the environment of Cu(PMT)4 (0104)2 in nitrobenzene is similar to the environment in sea m.~H ma mmo.~ ooh mm~.~ NaoavazsmmUZNAmmov-svoo on «AoevofizommozNAmmov-¢voo sea m.Na on mmo.~ HRH mmN.~ NaoavsAzemmommo-sveo ca Nahevmazommommo-ov=o sea ~.aa ea moo.~ mam osN.~ NAeOHUVoAzommozo-svoo ca NAooHovoAzommozo-evoo sea ~.aa ma cmo.N Nos om~.~ NAoHVvoCaoaoanvoo ca mes oo.~ oaa moN.~ Mascaovsaoaaoaoaovoo toooaaooo ca «as o.Na om omo.~ was omm.~ Namozvqxoswoansnv+m on Aocfikuhavso am $0.50 A. __ ._. __ __ -nomom AH-sooova.< A so cavn_ < w AH-Eos0avmw < w mocmwwq wcwvcom cowouuwz :uHS moxodanu AHHVSU uom mung Mmm >N mumcw mwsHt 58H HNH qm.m ououooe fianuo cw Namozvoo osa Nam sowsAmmzvso « oo.~ sod mom.~ oooanosonoaa ca NAoODUVoAHZmVoo « ~H.N mam wmm.~ nowswn oowoaaooo A odov AHvaoo t wo.~ RAH mwN.N odouconouuwa SH ~A¢0aovsaezmvoo t no.N owH mwN.~ nopsoa pousfiwocn mascaovsaazmvoo . __ a : __ uuo o I. I . w II a a Aa-sosoHvz a Aa-aosoavz a Aa-sosoHvoo < w Aooooaocoov sx mamaa 2156 H -e O Figure 39. The ESR Spectra of Undiluted Cu(PMT) (Cth)2 (top) and Cu(PMI')6(C10’+)2 powder (bogétom). 3157 158 the pure powder with the complexes having definite tetra- gonal symmetry, as expected, since Cu(II) normally pre- fers a tetragonal crystal field stabilization. A quantitative calculation of the molecular orbital coefficients cannot be made since the d-d electronic trans- itions could not be assigned from the visible reflectance and solution spectra which gave only one broad band which probably contains the three expected transitions. However, a comparison of the ESR All data for the PMT complexes with the other nitrogen bonding complexes listed in Table XV indicates that for Cu(PMT)u(0104)2 the PMT is a less basic ligand than the pyridine in Cu(pyridine)u(0104)2 complex. The difference in the ESR data between Cu(pyridine)4(NO3)2 and Cu(pyridine)4(TS)2b, shows that the ligands in the axial positions can have a large effect on the experimental AII values so that a further comparison with the other complexes would be of uncertain validity. st = Retoluenesulfonate anion.