3"» ‘g . “ASS SPECYML MOSES OF SOME WBSHTUTED PHOSPHENES Them foo $1 0m 9‘ M; 8. WWW STATE WEEKS!!! Wfifiiiam Zane Borer 1968 THESIS - “115‘ ’ J LIBRARY Michigan State University Am—m v-H‘ .- ABSTRACT MASS SPECTRAL STUDIES OF SOME SUBSTITUTED PHOSPHINES by William Zane Borer The mass spectra of a selected group of substituted halophosphines and aminohalophosphines are reported. The main features of the spectra of analogous series of compounds are compared and contrasted. Fragmenta- tion, rearrangement, recombination, and metastable transitions are dis- cussed. Correlations are drawn between relative molecular stabilities under electron-impact. When possible, conclusions are compared to those drawn from other physical data for the compounds under investigation. Suggestions for future work are made. MASS SPECTRAL STUDIES OF SOME SUBSTITUTED PHOSPHINES By William.Zane Borer A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Chemistry 1968 ACKNOWLEDGMENTS The author wishes to express sincere thanks to Professor Kim Cohn for his guidance and personal interest throughout the course of this research. He would also like to thank Mr. David E. Lewis for contributing the aminOphosphines used in this work. ii TABLE OF CONTENTS Page INTRODUCTION ........................................ 1 HISTORICAL .......................................... 2 RESULTS AND DISCUSSION .............................. 5 General ....................................... 5 Tris(dimethylamino)phosphine .................. 7 The Bis(dimethylamino)phosphines .............. 8 The Dimethylaminodihalophosphines ............. 9 The Methyldihalophosphines .................... 11 The Substituted Difluorophosphines ............ 14 Suggestions for Future Work ................... 15 DATA AND EXPERIMENTAL ............................... 16 Instrumentation and Purity of Compounds ....... 16 Preparation of Compounds ...................... 16 Data .......................................... 17 BIBLIOGRAPHY ........................................ 42 iii TABLE II. III. IV. VI. VII. VIII. IX. XI. XII. XIII. XIV. XV. XVI. XVII. XVIII. XIX. XXII. LIST OF TABLES Relative Intensities of Principal Ions ......... Percent Total Ionization of Principal Ions ..... Stretching Force Constant from Normal Coordinate Calculations for Molecules of the Type (CH3)2NPX2 ......................... Mass Spectrum of Dimethylamine ................. Mass Spectrum of Tris(dimethylamino)phos- phine .......................................... Mass Spectrum of Bis(dimethylamino)fluoro- phosphine ...................................... Mass Spectrum of Bis(dimethylamino)chloro- phosphine ...................................... Mass Spectrum of Bis(dimethylamino)bromo- phosphine ...................................... Mass Spectrum of Dimethylaminodifluoro- phosphine ...................................... Mass Spectrum of Dimethylaminodichloro- phosphine ...................................... Mass Spectrum of Dimethylaminodibromo- phosphine ...................................... Mass Spectrum of Phosphorus Trifluoride ........ Mass Spectrum of Phosphorus Trichloride ........ Mass Spectrum of Phosphorus Tribromide ......... Mass Spectrum of Dimethylaminotetrafluoro- phosphorane .................................... Mass Spectrum of Methyldifluorophosphine ....... Mass Spectrum of Methyldichlorophosphine ....... Mass Spectrum of Difluorochlorophosphine ....... Mass Spectrum of DifluorobromophOSphine ........ Mass Spectrum of Difluoroiodophosphine ......... Mass Spectrum of Difluorophosphine ............. Mass Spectrum of CyanodifluorOphosphine ........ iv Page 12 l3 14 18 19 21 23 25 27 28 3O 32 32 33 34 35 36 37 38 39 4O 41 INTRODUCTION As a result of the developments in the field of synthetic inorganic chemistry during the past two decades, a number of new substituted phos- phines have been preparedl'6. Refinements in physical methods and theo— retical approaches have made possible studies of the bonding and molecu- lar structure of these new compounds7’9. This work is concerned with the investigation of the positive-ion mass spectra of a selected group of substituted haloPhosphines and amino- halophosphines. The study was undertaken to compare the mass spectral data of analogous series of compounds, to draw correlations between molecular stabilities under electron-impact, and to compare relative bond strengths. The results obtained are then compared to existing physical data which has been reported for some of these compounds. HISTORICAL Until recently the develOpment of mass spectrometry has been ori- ented toward the design and improvement of methods for the investigation of organic compounds, particularly those of interest to the petroleum industry. Only within the last fifteen years has the utility of mass spectrometry received renewed attention by the inorganic chemist. Several relatively simple inorganic species have been subjected to electron-impact studies. Recently, work in the field of mass spectro- metry has begun to include larger, more complex inorganic moleculele-lh. Extensive electron—impact studies have been conducted on the phos— 19-23 and heats of form- phorus hydridesls'l9. The appearance potentials ationl9’23 of the most abundant ion fragments from phosphine have been reported by several authors. The ion-molecule reactions of phosphine in a mass spectrometer have been investigatedzh. Somewhat fewer studies have been carried out on the phosphorus trihalides, however the mass spectra of phosphorus trichloride25’26 and phosphorus tribromide27 have been reported, and the appearance potentials and heats of formation of the most abundant ions have been calculated. The surprisingly low appearance potential of the P01 + ion prompted 26 2 Halmann and Klein to investigate the negative-ion spectrum of phos- phorus trichloride. They showed that Cl' was produced in high abundance, and that the formation of P012+ could be explained by its production, together with Cl‘, in an ion pair. This study is relatively unique be- cause most work in mass spectrometry is concerned with the observations of positive ions formed by processes such as M + e‘-—a>M+ + 2e” where + O O O O M 18 the molecular ion, or if fragmentation occurs, 2 M + e'-——9» m+ + n + 2e' where m+ is an ion-fragment and n is a neutral fragment. Work carried out on the alkyl-substituted phosphinesl7’22’28 in- cludes mass Spectral cracking patterns and appearance potentials for the methyl and ethyl substituted compounds. Williams, Ward, and Cooks29 have undertaken a somewhat more saphisticated study of some organo-phos- phorus compounds. They have used deuterium labeling to study reactions induced by electron-impact in triphenylphosphine, triphenylphosphine oxide and methylenetriphenylphosphorane. Other authorsso-32 have carried out mass spectral investigations of the fluoroalkyl and fluoroaryl derivatives of phosphorus in order to gain more information about molecular rearrangements and mechanisms for the transfer of fluorine from carbon to phosphorus. Miller30 has examined the mass spectra of a series of pentafluorOphenyl derivatives of phos- phorus. Bond-forming rearrangements were observed such as the elimina- tion of PF2 from the (C6F5)2P+ species giving (C6F4)2+' Cavell and Dobbie31’32 have observed extensive rearrangement and transfer of fluorine during the fragmentation of the trifluoromethylphosphines. The mass spectra of the dimethylaminohalophosphines are of particular interest because of recent investigations which have demon- strated the ability of the phosphorus atom to act as a Lewis base in the 1 presence of various electron acceptors. Difluorochlorophosphine has been prepared by allowing hydrogen chloride to react with dimethylaminodifluoro- phosphine, (CH3)2NPF2. Difluorobromophosphine1 has been prepared in a similar manner. The coordination chemistry of dimethylaminodifluorophosphine has been studied by several authors. Ter Haar and Sr. Fleming33 have shown that this ligand will displace carbon monoxide from BAHBCO to form BhH8[(CH3)2NPF2J. Schmutzler3b' has prepared Ni[(CH3)2NPF2]h and Mo(CO)3[KCH3)2NPFé]3 by a similar displacement of CO from metal carbonyls. Both Cavell and Sr. Fleming36 have independently reported the addition of BF3 to (CH3)2NPF2 in a 1:1 ratio. Cohn and Parry37 have prepared two new coordination compounds, CuCl [(CH3)2NPF2] and CuCl[(CH3)2NPF2]2 by allowing the ligand to react with anhydrous copper (I) chloride. The infrared and nmr spectra of these compounds suggest that bonding occurs through the phosphorus atom rather than the nitrogen atom37. A single crystal X—ray diffraction study by Douglas and Nordman9 has established that the coordinate bond is formed through phosphorus in BhH8[(CH3)2NPF2]. Cohn and Parry37 have postulated that the Lewis basicity of the phosphorus atom in the ligand is enhanced by donation of the nitrogen electron pair to the empty phosphorus d orbitals. A recent nmr study of chloro(dimethylamino)phenylphosphine38 has shown restricted rotation around the phosphorus-nitrogen bond. Rotational barriers in the order of 12 kcal/mol for P—N bonds38 are too large to be attributed to confor- mational effects of the kind operating in ethane or methylamine. For this reason Cowley, Dewar, and Jackson38 suggest that the barrier might be attributed to a lone-pair -— line-pair interaction. RESULTS AND DISCUSSION GENERAL A brief discussion of the mass spectral fragmentation patterns of alkyl amines is advantageous at_this point because 1) several of the phosphines discussed herein contain dimethylamino substituents and 2) phosphorus and nitrogen posess chemical similarities, both being Group V elements. Gohlke and McLafferty39 have shown that the mass spectra of a number of aliphatiC‘amines may be correlated with certain structural features. Amines which contain alkyl groups larger than methyl undergo cleavage of the.carbon—carbon bond adjacent to nitrogen. This cleavage, in_which the largest possible group is lost preferentially, provides the base peak.(or most abundant ion) in the spectrum. The in— tensity of the molecular ion decreases.regularly with increasing molec— ular weight. The hydrogen radical is eliminated only when no other al- ternative exists. The base peak in the mass spectrum of dimethylamine39 (Table IV) has a maBShtoacharge (m/e) ratio of M—l where M is the mass of the molecular'ion; The positive charge is stabilized on the nitrogen via the formatation of an immonium ion (eqn 1). -H (CH3 )2NH+—->H20=NHCH3+ ( 1) This stabilization of the positive charge by the heteroatom is not unique to the amines. Aliphatic alcohols eliminate a hydrogen radical to ho form the stable oxonium ion . The base peak in the mass spectrum of methanol (eqn 2) corresponds to the M—1 ion. McLaffertyhl points —H CH3OH+—> H2C=OH+ (2 ) out that the even electron fragment, whether ion or neutral generally has the greater stability and therefore exerts the greater influence on the the course of the degradation reaction. In the aliphatic thioethers there is an increased tendency toward cleavage of the carbon-sulfur bond with charge retention on sulfur. According to Budzikiewicz, Djerassi, and Williamshz this is because sulfur has a greater ability than oxygen to stabilize the electron deficiency by participation of inner shell electrons. Examination of the mass spectra of the alkyl-substituted phosphines shows a more pronounced cleavage of the carbon-heteroatom bond (as com- pared to the amines) because of the greater ability of phosphorus to ac— comodate an electron sexteth3. Loss of a methyl group provides the base peak in the spectrum of trimethylphosphine28 (eqn 3). (CH3)3PI-;C—H3>(CH3)2P:+ (3) The second strongest peak in the spectrum of trimethylphosphine is an ion of mass 59. This ion, which is also present in the spectra of other alkylphosphines, may be represented as a cyclic phosphiran structure a” or as a linear phosphonium ion b_or g}7. It is analogous to the immonium ion observed at m/e 42 in the spectrum of trimethylaminehh. P+ / \ -$_ P“ a c The main process in the fragmentation of the ethylphosphines is not the loss of a methyl radical as is the case with the analogous amines. Instead, the main cleavage involves the elimination of ethylene via a 28 rearrangement in which a phosphorus-hydrogen bond is formed . AS Budzikiewicz, Djerassi, and Williams suggest that the formation of a phosphonium ion is not as favored as the formation of the analogous im— monium species, probably because of better stabilization of the electron deficiency by phosphorus through participation of the d—shell. This hypothesis is supported by the abundance of ions of the type H3CPT, H CP+ 2 and HCPI in the mass spectra of the methyl phosphinesl7 and their higher homolog328. TRIS LDIMEWTHYLAMINOWHOSPHINE Upon examination of the mass spectrum of tris(dimethylamino)phosphine (Table V) a high abundance of two types of positive ions is apparent. The first type is the group of immonium ions with the positive charge stabilized by nitrogen, and the second is the group of disubstituted phosphorus ions of the general formula :PXY+ where X may or may not be identical to Y. The predominance of these two types of ions supports the hypothesisl‘L5 that the stabilization of the electron deficiency by phos- phorus is through participation of the d-shell rather than the formation of a phosphonium ion. Strong evidence for two metastable transitions* in the mass spectrum of tris(dimethylamino)phosphine was observed. The first of these trans— itions (eqn 4) results in the formation of the ion at m/e 119. The meta— stable peak occurs at m/e 87.0 and was calculated to be at m/e 86.9. The process which results in the formation of the ion at m/e T6 (eqn 5) in— volves a 1—3 hydrogen shift to phosphorus. The metastable peak was ob- served at m/e 48.6 and was calculated to be at m/e 48.5. This data is in agreement with the observations of othershT. m*86.9 [( CH3) 2N]3P+-—> [( CH3) 2N] 2P+ + (CH3)2N (h) m/e 163 m/e 119 m 44 * A metastable peak occurs when an ion of mass mo dissociates into a daughter ion of lower mass m and a neg ral fragment n between the ion t repeller plate and the magnetic field 6. The mass-to—charge ratio of the metastable peak m* is given by m* = m2/mo. m*48.5 [(CH3)2N]2P+—>(CH3)2NPH+ + CH2=NCH3 (5) m/e 119 m/e 76 m 43 Bratermanlo in a study of transition metal carbonyl derivatives of tris(dimethylamino)phosphine, has observed a similar rearrangement with a l-4 hydrogen transfer to the metal (eqn 6). + + — 3)2]3 —>HFeP[N(CH3)2]2 + CH2-NCH3 (6) The peak at m/e 60 in the spectrum of [KCH3)2N]3P is of interest FeP [N( CH because of its relatively high intensity. This ion can best be repre— sented as CH2=NPH+. The process which gives rise to this fragment is unknown. One possibility is the elimination of a neutral CH4 group from the ion at m/e 76, however there is no metastable evidence for such a transition. It is difficult to pinpoint the center of positive charge in the phosphorus containing ion; it seems likely that there is a sharing of the electron deficiency between the phosphorus and nitrogen atoms. The rela- tively high abundance of the immonium ion species suggests that during fragmentation, the amine nitrogen can accomodate the electron deficiency nearly as well as phosphorus. THE BIS(DIMETHYLAMINO)HALOPHOSPHINES The mass spectral data for this series of compounds has been sum- marized in Tables I and II. The most important ions have been tabulated according to relative intensity and percent total ionization. Comparison of the data in this way shows trends which are indicative of the relative stabilities of each of the molecules to electron—impact. The mass spectrum of [(CH3)2N]2PF exhibits features which make it unique among the spectra of the bis(dimethylamino)halophosphines. The number of different ion fragments is small compared to the number in the spectra of the chloro and bromo compounds. Occuring in the spectrum of the fluorophosphine are two fragments of the type (CH3)2NPX2+ and PX2+, which could not have arisen from simple fragmentation of the parent molecule. These ions, which do not occur in the spectra of the other two compounds, could have been formed by an ionwradical reaction involving atomic fluorine or they could have occured by disproportionation of the original compound in the heated ion source. The PF2+ ion has been shown to be an extremely stable species formed by rearrangement in the spectra of the fluoroalkyl3l’32 and fluorophenylphosphines30. The most abundant ion in the Spectrum of each of the bis(dimethyl— amino)phosphines is a disubstituted phosphorus fragment of the type :PXY+, where X=Y=(CH3)2N for the bromo compound. There is a higher abundance of immonium type ions in the spectra of the fluoro and chloro compounds than in the spectrum of the bromo compound (see Table II). Conversely there is a higher percentage of phOSphorus containing ions in the spectrum of the bromophosphine. The ion represented by the general formula (CH3)2NPX+ is of interest because it occurs in the spectrum of the fluorophosphine in a very high abundance. The percentage of this ion decreases sharply in the chloro compound and reaches a minimum in the bromo compound. This evidence suggests that there is a decrease in stability to electron—impact of the bis(dimethylamino)haIOphosphines as the atomic weight of the substituted halogen increases. THE DIMETHYLAMINODIHALOPHOSPHINES As would be expected, this series of compounds shows a higher abundance of fragments which contain phosphorus and halogen only (see Table II). In contrast to the bis(dimethylamino)halophosphines, 10 there are few fragments without a halogen which contain an amino group attached to phosphorus. Again the fluorine containing compound shows a considerably lower number of different positive ion fragments than the analogous dichloro and dibromOphosphines. In contrast to the series of bis(dimethylamino)halophosphines, (CH3)2NPF2 is the only member of the dihalophosphine series which shows a metastable transition (eqn 7). m*111.0 (CH3)2NPF2-2Ii'> C2HSNPF2 (7) m/e 113 m/e 112 The metastable peak was observed at m/e 111.0 and was calculated to be at m/e 111.0. This evidence suggests that the difluoro compound is the most stable to electron-impact of any of the other aminohalophosphines considered. It should be noted that the peak at m/e 112 arising from the metastable transition (eqn 7) is equally as intense as the molecular ion, M, at m/e 113. This suggests that when the molecule is subjected to electron—impact, the preferred method of accomodating the electron deficiency involves the elimination of a hydrogen radical with charge stabilization by an immonium nitrogen. This results in considerably less fragmentation of the M and M-1 ions. There are other trends in the series of dimethylaminodihalophosphines which are important. The PX3+ type fragment is absent in the spectrum of the difluorophosphine, however this ion is present in low abundance in the spectra of the other two compounds. This suggests that the possi— bility of recombination (or disproportionation) is greater for the dichloro and dibromophosphines than for the difluoro compound. (Again the heated ion source may be responsible for this.) The abundance of the ion with ) NPX+ increases with increasing atomic weight 3 2 of the halogen substituent (Table II). This is in direct contrast to the the general formula (CH ll behavior of the bis(dimethylamino)halophosphines. The decreasing abun- dance of the molecular ion with increasing molecular weight further suggests that the dichloro and dibromo compounds are considerably less stable to electron—impact than is the difluoro compound. This conclusion is in agreement with the data calculated by Farran7 (Table III) for the phosphorus—halogen force constants in compounds of the general formula (CH3)2NPX2. Mass spectral data for the phosphorus trihalides are in— cluded in Tables I and II for purposes of comparison. The mass spectrum of dimethylaminotetrafluorophosphorane is report— ed in Table XV. This compound is of interest because of its similarity to dimethylaminodifluorophosphine and because of its unusual stability to electron—impact. Miller30 has observed no molecular ions in the mass spectra of such compounds as (C6F5)3PC12 and (C6F5)2PC13 even after re- duction of the ionizing voltage from 70 to 40 eV. Kennedy and Payneh8 detected a very weak molecular ion peak in the spectrum of PF3C12 at an 49 ionizing voltage of 15 eV. Rogowski and Cohn observed no molecular ions in the spectra of PFhCl and PFhBr at 56 eV. Demitras and MacDiarmidSO, however have reported a molecular ion peak at m/e 151 with a relative intensity of 19% in the mass spectrum of (CH3)2NPFh. This compares well with the results of this work in which the molecular ion in the spectrum of (CH3)2NPFh had a intensity of 19.5% relative to the PF4+ base peak. THE METHYLDIHALOPHOSPHINES The mass spectra of CH3PF2 and CH3PC12 are reported in Tables XVI and XVII respectively. As might be expected, the base peak in both of these spectra is the PX2+ ion. The molecular ion in each spectrum has a relative intensitv of 42 - 43% of the base peak. The majority of the ION RELATIVE INTENSITIES OF PRINCIPAL IONS“ 12 TABLE I A = [(CH3)2N] APCl APBr PF PCl PBr A3P A2PF A2PC1 A2PBr APF2 2 2 3 3 3 [(0113 )ZN]3P+ 27. 5 [(CH3)2N]2P+ 100.0 34.4 100.0 (CH3)2NHP+ 97.7 2.6 44.7 84.3 CH3NP+ 41.8 5.1 36.0 44.2 11.9 17.3 (CH3)2N+ 85.5 31.7 39.6 21.3 4.0 17.0 18.8 (CH2)2N+ 33.7 42.7 45.5 41.6 100.0 78.1 43.4 CH3+ 47.4 34.3 41.2 38.8 32.4 54.8 25.7 [KCH3)2N]2PX+ 19.7 36.9 6.0 (CH3)2NPX+ 100.0 100.0 26.8 12.2 100.0 100.0 (CH3)2NPX2+ 6.5 54.1 37.9 7.8 2+ 2.7 5.6 2.0 19.2 8.8 7.1 13.3 33.9 Px+ 3.5 9.9 6.4 19.5 14.5 9.3 14.9 29.7 Px2+ 4.7 29.1 67.7 10.3 100.0 100.0 100.0 Px3+ 22.1 3.3 46.7 41.6 65.0 xi 20.0 9.4 22.3 71.6 * Peaks representing ions which differ only in isotopic composition are summed for the purposes of this table. If the intensity of the base peak is affected, the intensities of the other peaks are normal— ized accordingly. 13 TABLE II PERCENT TOTAL IONIZATIONO OF PRINCIPAL IONS* ION A3P A2PF A2PC1 A2PBr APF2 APCl2 APBr2 PF3 9013 PBr3 [(CH3)2N]3P+ 6.3 [(TCH3 ) 2N:]2P+ g3,_1 9.0 _2_6_._4 (CH3)2NHP+ 22.5 1.0 11.7 22.1 CH3NP+ 9.6 2.0 9.4 11.7 2.7 6.7 (CH3)2N+ 19.7 12.6 10.4 5.6 1.7 3.8 7.3 (CH2)2N+ 7.8 17.0 11.9 11.0 4;:§_ 17.4 16.7 CH3 10.9 13.7 10.8 10.2 13.5 12.2 9.9 [(CH3)2N]2PX+ 7.9 9.7 1.6 (CH3)2NPX+ 39.8 26.3 7.1 5.1 22.3 38.6 (CH3)2NPX2+ 2.6 22.5 8.4 3.0 P+ 0.7 1.5 0.8 4.3 3.4 4.6 6.9 11.3 PX+ 1.4 2.6 2.7 4.4 5.6 5.7 7.8 9.9 PX2+ 1.9 12.1 15.1 4.0 61.3 52.1 33.3 Px3+ 4.9 1.3 28.7 21.7 21.6 x+ 4.5 3.6 11.6 23.9 0 Defined as :(Int)n where n includes only those ions appearing in the table. * Base peak is underlined. 14 remaining fragments are of the PXYI type mentioned previously. There is a low abundance of phosphonium type ions in both spectra. TABLE III Stretching Force Constants from Normal Coordinate Calculations for Molecules of the Type (CH3)2NPX 7 2 Bond Force Constant — mdynes/A P—N 6.5 i 0.8 P-F 4.0 2 0.4 P-Cl 1.7 t 0.2 P-Br 0.85 i 0.09 THE SUBSTITUTED DIFLUOROPHOSPHINES The mass spectra of PF2C1 and PF2Br are reported in Tables XVIII and XIX respectively. The base peak in both of these spectra corresponds to the PF2+ ion. Both compounds showed recombination (or disproportionation) to give a relatively high abundance of PFBI. The presence in low abun— dance of ions containing both oxygen and hydrogen indicate that a small amount of hydrolysis occurred. This probably took place in the inlet system of the mass spectrometer, since vapor pressure measurements showed less than 1% impurity in the compounds. The.mass spectrum of PF I has been reported by Rudolph51 (Table XX). 2 The molecular ion provides the base peak in the spectrum of this compound. Because this spectrum was obtained with the same type of instrument and at the same ionizing voltage as the other compounds in this series, a comparison of the spectra of the three substituted difluorohaIOphosphines can be made. The molecular ion in the spectrum of PF2Br has a higher relative intensity than the molecular ion in the spectrum of PF2CI. The PF2+ ion in the spectrum of PFQI has a relative intensity of 60% of the PFQI+ 15 base peak. The PF3+ recombination peak in the spectra of the three phos- phines shows a decrease in relative intensity as the molecular weight of the compound increases. This data suggests that there is an increase in stability to electronvimpact of the difluorohalophosphines with increasing molecular weight. This represents a reversal of the trend shown in the series of dimethylaminohalophosphines. The mass spectra of difluorOphOSphine and cyanodifluorophosphine have also been reported by Rudolphsl. These are included in Tables XXI and XXII respectively. The base peak in the spectrum of PHF2 corresponds to the molecular ion, however PF2+ provides the base peak in the spectrum of PF2CN. schESTIOngFOR FUTURE WORK Other investigations which would enlarge the scope of this work can be recommended. Determination of the appearance potentials of key positive ions in the spectra of the compounds discussed would provide a quantitative basis for calculation of the ionization potentials and heats of formation of the ions. In this way the stabilities of the molecules to electron— impact could be more rigorously compared. Studies of the negative—ion spectra of these compounds would provide information concerning ion pair .production. Investigations of ion-molecule reactions in a mass spectrov meter could lead to the proposal of mechanisms for the formati8n of ions by recombination. Because thermal effects in the heated ion source of a 52 mass spectrometer can cause errors in data interpretation , studies could be conducted which would determine the nature and extent of thermal reactions in the substituted phosphines. 16 DATA AND EXPERIMENTAL INSTRUMENTATION AND PURITY 0F COMPOUNDS All mass spectra were determined with a Consolidated Electrodynamics Corporation Model 21—103C mass spectrometer using the gas inlet system and a nominal source pressure of 4x10"5 torr. The ionusource temperature was 2500 C. The ionizing voltage used was 70 eV. The purity of all compounds with boiling points above 250 C was determined to be greater than 99% by vapor-phase chromatography. The instrument used was an Aerograph Model A90—P3 with Sargent Recorder SR. The column was 5'x%" packed with 20% SE—30 on Chromosorb W. The purity of all compounds with boiling points below 250 C was determined to be greater than 99% on the basis of vapor pressure data. PREPARATION OF COMPOUNDS The compounds discussed were prepared, purified, and characterized by the most convenient literature methods, some with slight modifications which are noted herein. The tris(dimethylamino)phosphine was prepared by the method of Burg and Slota2. A minor modification of the method involv— ed the addition of the dimethylamine through a dry ice condenser into the reaction flask containing phosphorus trichloride dissolved in ether. The bis(dimethylamino)chlorophOSphine was prepared by the method of N0th and Vetterh. The bis(dimethylamino)fluorophosphine was prepared by fluorinating [(CH3)2N]2PC1 using zinc difluoride. The method was adapted from a description of the preparation of (CH3)NPF2 by Ngth and Vetters. The bis(dimethylamino)bromophosphine and dimethylaminodibromo- phosphine were prepared as described by Ngth and Vetterh. 17 Dimethylaminodichlorophosphine, dimethylaminodifluorophosphine, difluorochlorophosphine and difluorobromophosphine were all prepared by the methods of Morse, Cohn, Rudolph and Parryl. The methyldichlorophosphine was obtained from The Department of the Army, U.S. Army Edgewood Arsenal, Edgewood Arsenal, Maryland. This compound was redistilled before use to assure maximum purity. The methyldifluorophosphine was prepared by the method of Seel, Rudolph, 6 and Budenz . DATA The mass spectra are tabulated according to the relative intensities of the ions based on the most abundant ion in the spectrum. All the ions with greater than 2% relative intensity are reported. In some cases ions of special interest with relative intensities below 2% are reported. 18 TABLE IV MASS SPECTRUM OF DIMETHYLAMINE Relative Intensity m/e This Work Othersa Othersb Assignment 15 17.5 20 0 0H3+ 18 17.2 16 14 NHh+ 27 6.0 8 3 28 47.3 68 26 N2+ 29 3.0 2 30 7.5 13 4 CHZNH2+ 39 2.3 40 4.7 41 4.2 3 42 15.3 19 15 CZHhN+ 43 12.3 14 13 0211511+ 44 100.0 100 100 02th+ 45 53.9 51 56 C2H7N+ a See reference 53. b See reference 39. m/e 15 17 18 27 28 29 30 32 33 39 40 41 42 43 44 45 46 47 59 60 61 19 TABLE V MASS SPECTRUM OF TRIS(DIMETHYLAMINO)PHOSPHINE Relative Intensity 47.4 3.3 21.2 7.2 54.3 3.6 15.0 3.3 3.9 5.0 5.8 33.7 13.6 85.5 37.9 3.6 4.7 3.8 41.8 2.4 Assignment CH3+ NHh+,H20+ N2+ CH2NH2+,CH2NPH++ C2HhN+ 02H5N+ , + C2H6N + C2H7N + CH2NPH Metastable m” 48.5 m” 86.9 TABLE v (Continued) 2O MASS SPECTRUM OF TRIS(DIMETHYLAMINO)PHOSPHINE m/e Relative Intensity 74 2.2 75 11.1 76 97.7 77 2.9 81.5 3.6 94 3.7 110 h,h 119 100.0 120 5.5 163 27.5 164 2.2 peaks (see eqn 5 page 8) (see eqn 4 page 7) Assignment + C2H5NP + (CH3)2NP + (CH3)2NPH 2 [(0113 )2N]3P+ + (CH ) NPH + 3 2 [(0113 )2N] QP“ [( CH3 )2N] 2PH+ [( CH3 )2N13P+ [( CH3 )2N] 2PH+ 21 TABLE VI MASS SPECTRUM 0F BIS(DIMETHYLAMINO)FLUOROPHOSPHINE m/e 15 16 17 18 27 28 29 30 40 41 42 43 44 45 50 51 60 65 69 76 Relative Intensity 34.3 2.1 19.5 77.8 2.6 13.4 2.0 16.2 2.6 4.0 42.7 5.9 31.7 2.6 3.5 6.1 5.1 5.2 4.7 2.6 Assignment 4.. CH3 NHh+,H2O+ + N2 + ++ CH2NH2 ,CHZNPH C2HhN+ C2H5N+ + C2H6N + C2H7N PF+ PHF+ + CH2NPH (CH3)2NH-HF+ ? + PF2 + (CH3)2NPH 22 TABLE VI (Continued) MASS SPECTRUM OF BIS(DIMETHYLAMINO)FLUOROPHOSPHINE m/e 78 80 93 94 95 112 113 138 Relative Intensity 7.6 1.7 7.0 100.0 5.2 6.3 6.5 19.7 Assignment 4. CH2NPF C2H5NPF+ (CH3)2NPF+ (CH3)2NPHE+ C2H5NPF2+ (CH3)2NPF2+ [( CH3 )2N] 2PF+ 23 TABLE VII MASS SPECTRUM OF BIS(DIMETHYLAMINO)CHLOROPHOSPHINE m/e Relative Intensity Assignment 15 54.2 CH3+ 18 6.6 NHh+,H20+ 27 3.5 28 25.8 N2+ 30 12.6 CH2NH +,CH2NPH++ 31 3.5 P+ 32 5.4 33 6.6 36 2.8 40 3.5 41 6.0 42 59.8 C2HuN+ 43 9.4 C2HSN+ 44 52.0 0211611+ 45 8.2 02H7N+ 46 4.4 47 6.3 58 2.3 59 7.8 CH2NP+ 60 47.3 CH2NPH+ 67 4.1 TABLE v11 (Continued) 24 MASS SPECTRUM OF BIS(DIMETHYLAMINO)CHLOROPHOSPHINE m/e Relative Intensity 69 2.2 74 2.6 75 13.5 76 58.8 77 2.6 81 3.1 94 6.1 96 2.4 109 5.4 110 100.0 111 2.4 112 31.4 119 45.5 120 2.6 154 36.5 156 12.0 Metastable peak m” 48.5 (see eqn 5 page 8) Assignment + C2H5NP + (CH3)2NP (CH NPH+ 3)2 + (CH3)2NPH2 (CH3)2NHcH3SCl+ ? CH2NP3501+ CH2N1>3701+ C2H5NP3SCI+ (CH3)2NP3501+ 0211511193701+ (CH NP37Cl+ 3)2 [( CH3 >211] 212* [( CH3 ) 2N] 2211* U CH3 >217] 2R3501+ [(CH3)2R]2P3701+ 25 TABLE VIII MASS SPECTRUM OF BIS(DIMETHYLAMINO)BROMOPHOSPHINE m/e Relative Intensity Assignment 15 38.8 CH3+ 18 4.5 NHh+,H2O+ 27 2.9 28 17.5 30 8.0 CH2NH2+,CH2NBH++ 31 5.6 P+ 32 4.3 33 5.9 40 2.7 41 5.1 42 41.6 02111.1(+ 43 6.2 C2H5N+ 44 21.3 C2H6N+ 45 5.9 C2H7N+ 46 3.8 47 6.2 59 7.3 CH2NP+ 60 44.2 CH2NPH+ 74 2.9 C2H5NP+ + 75 15.9 (CH3)2NP 26 TABLE VIII (Continued) MASS SPECTRUM OF BIS(DIMETHYLAMINO)BROMOPHOSPHINE m/e Relative Intensity Assignment 76 84.3 (CH3)2NPH+ 77 2.4 (CH3)2NPH2+ 85 2.9 94 2 . 9 110 7.2 979Br+ 112 2.7 P81Br+ 119 100. 0 [( CH3 )2N] 29+ 120 5 . 3 [( CH3 ) 2N] 2TH+ 124 7.7 154 13.4 (CH3)2NP79Br+ 156 13.4 (CH3)N981Br+ 198 3. 0 [(0113 )2NJ2P79Br+ 200 3 . 0 [( CH3 ) 2N] 2P81Br+ Metastable peak m* 48.5 (see eqn 5 page 8) 27 TABLE IX MASS SPECTRUM OF DIMETHYLAMINODIFLUOROPHOSPHINE m/e Relative Intensity Assignment 15 32.4 CH3+ 18 .4 NH4+,H20+ 27 2.5 28 31.1 N2+ 30 3.8 CHZNH2+ 31 2.0 P+ 32 7.1 40 4.5 41 5.6 42 100.0 C2H4N+ 43 10.2 02H5N+ 44 4.0 C2H6N+ 50 .4 PF+ 51 3.5 CH3NH2.HF+ 2 65 2.0 (CH3)2NH-HF+ 2 69 29.1 PF2+ 78 3.2 CHZNPF+ 94 12.2 (CH3)2NPF+ 112 54.1 CZHSNPF2+ 113 54.1 (CH3)2NPF2+ Metastable peak m* 111 (see eqn 7 page 10) 28 TABLE X MASS SPECTRUM OF DIMETHYLAMINODICHLOROPHOSPHINE m/e Relative Intensity Assignment 15 70.2 CH3+ 18 9.1 NH4+,H20+ 26 .5 27 6.3 28 25.6 N2+ 29 3.2 30 17.2 CHZNH2+,CH2NPH'++ 31 24.6 P+ 32 .7 33 6.0 35 19.3 3501+ 36 15.1 H3501+ 37 6.3 37C1+ 38 5.3 H3701+ 39 3.2 40 6.0 41 9.1 42 100 0 C2H4N+ 43 29.1 02H5N+ 44 21.8 C2H6N+ 45 8.1 02H7N+ 46 3.2 C2H8N+ 47 4.6 50 2.5 58 3.8 CHNP+ 59 4.5 CHZNP+ 60 15.3 CHZNPH+ 61 2.0 CH3NPH+ 66 18.5 P3501+ 29 TABLE X (Continued) MASS SPECTRUM OF DIMETHYLAMINODICHLOROPHOSPHINE m/e Relative Intensity Assignment 67 5.9 1123501+ 68 6.5 P3701+ 69 3.1 H237C1+ 81 4.8 85 5.2 94 10.5 101 49.0 P35012+ 103 32.2 P35013701+ 105 5.4 237012+ 109 2.5 110 96.9 (CH3)2NP35C1+ 111 3.4 (CH3)2NPH35C1+ 112 31.2 (CH3)2NP37C1+ 113 0.9 (CH3)2NPH37C1+ 129 .2 136 12.4 P35C13+ 138 11.7 2350123701+ 140 .8 P350137Clz+ 142 .4 237013+ 144 .3 CZHSNP35C12+ 145 27.7 (CH3)2NP35012+ 146 2.9 CZHSNP350137C1+ 147 17.8 (CH3)2NP35013701+ 148 0.9 CZHSNP37012+ 149 .1 (CH3)2NP37C12+ 30 TABLE XI MASS SPECTRUM OF DIMETHYLAMINODIBROMOPHOSPHINE m/e Relative Intensity Assignment 15 50.2 CH3+ 18 4.7 NH4+,H20+ 27 3.8 28 21.3 N2+ 29 2.2 30 9.7 CHZNH2+,CH2NPH++ 31 17.2 P 32 7.8 33 6.0 36 2.5 40 4.7 41 8.2 42 84.6 C2H4N+ 43 10.3 02H5N+ 44 36.7 02H6N+ 45 8.2 C2H7N+ 46 3.4 47 5.0 58 3.1 CHNP+ 59 7.9 CHZNP+ 60 33.8 CHZNPH+ 74 2.6 CZHSNP+ 75 11.0 (CH3)2NP+ 79 .1 79Br+ 81 9.3 81Br+ 110 17.7 P79Br+ 111 3.3 HP79Br+ 112 10.6 P813r+ 113 3.2 HP81Br+ 31 TABLE XI (Continued) MASS SPECTRUM 0F DIMETHYLAMINODIBROMOPHOSPHINE m/e Relative Intensity Assignment 125 2.5 127 2.5 154 100 0 (CH3)2NP79Br+ 155 3.3 (CH3)2NPH79Br+ 156 95.1 (CH3)2NP818r+ 157 2.8 (CH3)2NPH81Br+ 189 5.3 P79Br2+ 191 9.9 P79Br81Br+ 193 4.8 P81Br2+ 233 4.0 (CH3)2NP79Br2+ 235 7.5 (CH3)2NP79Br81Br+ 237 3.7 (CH3)2NP81Br2+ 268 0.9 P79Br3+ 270 2.5 P79Br281Br+ 272 2.3 P79Br318r2+ 274 0.7 P81Br3+ 32 TABLE XII MASS SPECTRUM OF PHOSPHORUS TRIFLUORIDE m/e Relative Intensity Assignment 31 7.1 P+ 50 9.3 PF+ 69 100.0 252+ 88 46.7 PF3+ TABLE XIII MASS SPECTRUM OF PHOSPHORUS TRICHLORIDE m/e Relative Intensity Assignment 31 23.4 2+ 35 29.8 3501+ 37 9.3 3701+ 66 19.3 P3501+ 68 6.9 P3701+ 101 100.0 P35C12+ 103 64.9 P35013701+ 105 10.7 P37012+ 136 32.0 P35Cl3+ 138 29.8 P3501237CI+ 140 10.1 P350137012+ 142 1.2 P3701 + 3 m/e 31 79 81 110 112 189 191 193 268 270 272 274 33 TABLE XIV MASS SPECTRUM OF PHOSPHORUS TRIBROMIDE Relative Intensity 67.8 72.2 71.1 30.0 29.4 51.1 100.0 48.9 17.2 48.9 47.8 16.1 Assignment P+ 79Br+ 8131.+ P79Br+ P8lBr+ P79Br2+ P7gBr81Br+ P81 P798r3+ P79Br281Br+ P79Br81Br2+ P81Br3+ Br2+ 34 TABLE XV' MASS SPECTRUM OF DIMETHYLAMINOTETRAFLUOROPHOSPHORANE m/e Relative Intensity Assignment 15 26.9 CH3+ 17 3.0 18 11 7 NH + H 0+ ‘ 4 ’ 2 28 16.1 N2+ 40 3.6 41 .2 42 39.2 C2H4N+ 43 29.4 02H5N 69 5.3 PF + 88 4.1 PF3+ 91 2.0 107 100.0 PF + 4 + 116 3.4 CHZNPF3 132 15.0 (CH3)2NPF3+ 150 2.4 (c2H5)NPF4 151 19.5 (CH ) NPF + 3 2 4 MASS SPECTRUM OF METHYLDIFLUOROPHOSPHINE m/e 15 17 18 28 31 44 45 50 63 65 69 83 84 C See reference 6. 35 TABLE XVI 8.7 4.0 14.0 2.3 4.8 5.6 11.5 6.3 2.0 10.2 100.0 5.0 42.3 Relative Intensity This Work Othersc 0.8 17.6 5.2 1.9 1.4 100.0 4.9 37.7 Assignment m/e 15 18 28 31 35 36 37 38 43 44 45 46 47 66 67 68 79 80 81 82 83 101 103 105 116 118 120 36 TABLE XVII Relative Intensity 10. 15. 43. 14. 28. 61. 13. 29. 100. 65. ll. 43. 28. O\ F‘ ¢~ C) m) C) F‘ ox a: £~ U1 0: h) C) P‘ n) m: 6: U1 0: a> a: C) \1 c> F“ a: MASS SPECTRUM OF METHYLDICHLOROPHOSPHINE Assignment CH + 3 + + NH4 ,H20 + H302 HBCPH+ P3501+ PH35C1+ 01123501+ CH P3501+ CH P35C1+,CHP37C1+ CH P37CI+ CH3P37CI 235012+ NOON 237012+ CH3P35C12+ CH3P35CI37CI+ p37 + CH3 C12 37 TABLE XVIII MASS SPECTRUM OF DIFLUOROCHLOROPHOSPHINE m/e Relative Intensity Assignment 18 3.7 H20+ 19 5.7 F+ 25 10.1 PF++ 28 29.2 N + 31 7.7 P3 32 .1 02+ 7 34.5 .0 PF2++ 35 .7 3501+ 36 14.4 H3501+ 37 2.3 3701+ 38 4.7 H37c1+ 44 .4 PF3++ 47 3.7 20+ 50 11.1 PF+ 66 2.4 POF+ 67 2.4 HPOF+ 69 100 0 PF + 85 7.9 PF§501,P0F2+ 86 5.1 HP0F2+ 87 2.2 PE37C1+ 88 30.6 PF3+ 104 11.5 PF235C1+ 106 3.9 PF237CI+ 38 TABLE XIX MASS SPECTRUM OF DIFLUOROBROMOPHOSPHINE m/e Relative Intensity Assignment 15 .2 CH3+ 19 4.4 F+ 25 .8 PF++ 28 15.0 82* 31 7.8 2+ 32 2.8 02+ 2 34.5 2.2 PF2++ 44 4.7 PF3++ 47 6.9 P0+ 50 13.0 PE+ 66 3.0 POF+ 67 5.1 HPOF+ 69 100 0 PF2+ 79 6.1 79Br+ 81 6.0 81Br+ 85 .0 P0F2+ 86 .2 HPOF2+ 88 23.0 PF + 110 1.0 P73Br+ 112 1.0 P813r+ 129 3.2 PT79Br+ 131 3.2 PF81Br+ 148 14.0 PF27gBr+ 150 14.0 PF 8113r+ m/e 196 177 158 127 88 69 63. 50 31 19 39 TABLE XX MASS SPECTRUM OF DIFLUOROIODOPHOSPHINE51 Relative Intensity 100 15 6 71 l 60 4 29 ll 3 Assignment + PFZI PFI+ 21+ 1+ +. PF3 . + PF2 12+ PF+ + F+ 40 TABLE XXI MASS SPECTRUM 0F DIFLUOROPHOSPHINE 51 m/e Relative Intensity Assignment 70 100 0 PHI2+ 69 52.4 PP2+ 51 84.3 PHE+ 50 27.5 PF+ 34.5 0.8 PF22+ 32 .9 PH+ 31 16.0 P+ 25.5 1.0 PHE2+ 25 3.0 PE2+ 20 0.6 HP+ 19 4.6 E+ 16 1.2 PH2+ 16.5 2.3 22+ 41 TABLE XXII MASS SPECTRUM OF CYANODIFLUOROPHOSPHINE 51 m/e Relative Intensity Assignment 95 27.1 PFZCN+ 88 2.0 PF3+ 76 14.2 PPCN+ 69 100.0 PF2+ 57 1.9 PCN+ 50 17.6 PE+ 43 1.8 PC+ 38 1.4 PECN2+ 31 13.3 P+ 27 12.6 HCN+ 26 9.6 CN+ 19 .6 + 14 2.5 N+ 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 42 BIBLIOGRAPHY V. G. Morse, K. Cohn, R. W. Rudolph, and R. W. Parry in "Inorganic Syntheses,” Vol. 10, E. L. Muetterties, Ed., McGraw-Hill Co., New York, N. Y., 1967, p. 147. A. B. Burg and P. J. Slota, Jr., J. Am. Chem. Soc., 29) 1108 (1958). H. No'th and H. J. Vetter, Chem. Ber., 25*.» 1505 (1961). H. Math and H. J. Vetter, ibid., &: 1109 (1963). H. N‘o'th and H. J. Vetter, ibid, 39, 1298 (1963). Von F. Seel, K. Rudolph, and R. 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