THE CHEMISTRY of SOME TRIPLUOROMETHYL-PHOSPHINES . by MIRZA ARSHAD ALI BEG B..Sc
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THE CHEMISTRY of SOME TRIPLUOROMETHYL-PHOSPHINES . by MIRZA ARSHAD ALI BEG B..Sc.(Hons.)f M.Sc. (Karachi), 1955» A thesis submitted in partial fulfilment of the requirements for the degree of DOCTOR OF PHILOSOPHY in the Department of Chemistry. We accept this thesis as conforming to the required standard© THE UNIVERSITY OP BRITISH COLUMBIA June, 1961. In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication' of this thesis for financial gain shall not be allowed'without my written permission. Department of ^^R^+^C&&^ The University of British Columbia, Vancouver 8, Canada. Date Af*Ql.tfc% /9£f GRADUATE STUDIES Wqp Pntuersttg of ^rtttsii Columbia Field of Study: Inorganic Chemistry Topics in Inorganic Chemistry H. C. Clark H. G. Heal FACULTY OF GRADUATE STUDIES Topics in Organic Chemistry L. D. Hayward D. E. McGreer A. Rosenthal R. Stewart Radiochemistry D. R. Wiles Seminar in Chemistry : R. Stewart Related Studies: PROGRAMME OF THE . Atomic Physics K. L. Erdman ! FINAL ORAL EXAMINATION Geophysics '. J. A. Jacobs Structure of Metals II V. Griffiths j FOR THE DEGREE OF E. Teghtsoonian DOCTOR OF PHILOSOPHY of M. ARSHAD A. BEG B.Sc. (Hons), M.Sc. (Karachi) PUBLICATIONS FRIDAY, JULY 28th, 1961 at 2:30 p.m. 1. Chemistry of the Trifluoromethyl Group, Part I, Complex For• mation by Phosphines containing the trifluoromethyl group. IN ROOM 342, CHEMISTRY M. A. A. Beg and H. C. Clark, Can. J. Chem., 38, 119, 1960. 2. Chemistry of the Trifluoromethyl Group, Part II, Nickel(II) COMMITTEE IN CHARGE Complexes of Trifluoromethyl-phosphines. M. A. A. Beg and H. C. Clark, Can. J. Chem., 39, 595, 1961. Chairman: D. M. MYERS 3. Chemistry of the Trifluoromethyl Group, Part III, Phenylbistri- W. A. BRYCE J. A. JACOBS fluoromethylphosphine and related Compounds. M. A. A. Beg H. C. CLARK J. P. KUTNEY and H. C. Clark, Can. J. Chem., 39, 564, 1961. j. A. CRUMB c. A. MCDOWELL J. HALPERN R. STEWART L. G. HARRISON E. TEGHTSOONIAN External Examiner: H. J. EMELEUS, C.B.E., Ph.D., D.Sc, A.R.C.S., F.R.S. University Chemical Laboratory, Cambridge, England ABSTRACT By reaction with methyl iodide, this phosphine also forms a new phosphonium compound, methyldiphenyltrifluoromethylphosphonium CHEMISTRY OF SOME TRIFLUOROMETHYL-PHOSPHINES iodide which is readily hydrolysed by cold water with the loss of the trifluoromethyl group. One particular aspect of the chemistry of the trifluoromethyl In general, phosphines containing one trifluoromethyl group group is its high electron-withdrawing power which reduces the donor show similar properties to those of their parent compounds, tri- properties of normally strong bases. This investigation has been methylphosphine and triphenylphosphine, while those containing two concerned with the chemistry of some phosphines containing this trifluoromethyl groups are very similar in their behaviour to tristri- group. For this purpose, substituted phosphines containing methyl or fluoromethylphosphine. phenyl and trifluoromethyl groups have been prepared. For the study of their donor properties, a series of addition compounds with boron The phosphines containing more than one CF3 group do not trifluoride, platinum(II) chloride and nickel(II) salts have been form addition compounds with boron trifluoride. The phenyl-tri- prepared. fluoromethyl-phosphines form more stable complexes than the methyl- trifluoromethyl-phosphines. The reported methods for preparing the methyl-trifluoromethyl- The phosphines containing up to two trifluoromethyl groups phosphines do not produce a good yield; therefore, an attempt has form complexes with platinum(II) chloride. A complex with tristri- been made towards a better understanding of the reactions. The fluoromethylphosphine could not be obtained. Except dimethyltri- phenyl-trifluoromethyl-phosphines have been prepared by reacting fluoromethylphosphine, which forms mainly a cis isomer, the other trifluoroiodomethane with a phosphorus compound containing a P-P phosphines, CHa(CF3)2P, C6H5(CF3).,P, and (C6H5)2CF3P form main• bond. Thus, a reaction with tetraphenylcyclotetraphosphine gives ly trans isomers. The non-occurrence of the tristrifluoromethylphos- phenylbistrifluoromethylphosphine and phenyltrifluoromethyliodo- phine complex and the production of mainly trans isomers of the phosphine, and reaction with tetraphenlydiphosphine gives diphenyl- above-mentioned phosphines has been interpreted in terms of steric trifluoromethylphosphine. The latter has also been prepared by re• phenomenon. action of trifluoroiodomethane with either triphenylphosphine or The phosphines containing more than one CF group do not diphenylchlorophosphine. S form complexes with nickel(II) salts. The nitrate complexes of These new phosphines are colorless liquids (except phenyltri- trimethylphosphine and dimethyltrifluoromethylphosphine are para• fluoromethyliodophosphine which is reddish-brown) of high boiling magnetic, while the dichloro, dibromo, diiodo, and dithiocyanato point. They are stable in air and cannot be hydrolysed with acid or complexes are diamagnetic. water, except the iodophosphine C(.HSCF3PI, which reacts with water A correlation of the various properties, for example boiling to give phenyltrifluoromethylphosphinic acid, a new oxyacid. Phenyl- points and heats of vaporization, has shown that the trifluoromethyl bistrifluoromethylphosphine can be hydrolysed with aqueous alkali substituted phosphines are not anomalous in the general family of to give fluoroform and phenylphosphonous acid. Diphenyltrifluoro- phosphines. methylphosphine, on the other hand, cannot be hydrolysed by aqueous An attempt has also been made towards a study of the infrared alkali, but reacts slowly with alcoholic potassium hydroxide to give' spectra of the phosphines and their compounds, and towards a cor• fluoroform and diphenylphosphinic acid. relation with the spectra of other phosphorus compounds. Finally, an approximate estimate of the "electronegativities" of a wide range The phosphines form a further series of new compounds by of substituted phosphines gives values which are in good agreement reaction with halogens. Phenylbistrifluoromethylphosphine reacts with the observed order of reactivities of the phosphines studied, and with iodine to form trifluoroiodomethane, but forms phenylbistri- assists in correctly placing the trifluoromethylphosphines in such a fluoromethyldibromophosphorane with bromine. This compound al• range, of compounds. so gives phenyltrifluoromethylphosphinic acid on aqueous hydrolysis, as obtained in the case of phenyltrifluoromethyliodophosphine. Be• sides forming the dibromophosphorane, diphenyltrifluoromethylphos- phine is the first trifluoromethyl-phosphine known to form a diiodo- phosphorane. It is interesting to note that diphenyltrifluoromethyl- phosphine is difficult to hydrolyse, whereas the phosphoranes can be hydrolysed easily, giving fluoroform and diphenylphosphinic acid. (i) ABSTRACT One particular aspect of the chemistry of the tri• fluoromethyl group is its high electron-withdrawing power which reduces the donor properties of normally strong bases* This investigation has been concerned with the chemistry of some phosphines containing this group. For this purpose, substituted phosphines containing methyl or phenyl and tri• fluoromethyl groups have been prepared. For the study of their donor properties, a series of addition compounds with boron trifluoride, platinum(Il) chloride and nickel(II) salts have been prepared. The reported methods for preparing the methyl- trifluoromethyl-phosphines do not produce a good yield; therefore, an attempt has been made towards a better under• standing of the reactions. The phenyl-trifluoromethyl- phosphines have been prepared by reacting trifluoroiodo- methane with a phosphorus compound containing a P-P bond. Thus, a reaction with tetraphenylcyclotetraphosphine gives phenylbistrifluoromethylphosphine and phenyltrifluoromethyl- iodophosphine, and reaction with tetraphenyldiphosphine gives diphenyltrifluoromethylphosphine. The latter has also been prepared by reaction of trifluoroiodomethane with either triphenylphosphine or diphenylchlorophosphine. (ii) \ These new phosphines are colorless liquids (ex• cept phenyltrifluororaethyliodophosphine which is reddish- brown) of high boiling point. They are stable in air and cannot be hydrolysed with acid or water, except the iodo- phosphine C H CP PI, which reacts with water to give phenyl- 6 5 3 trifluoromethylphosphinic acid, a new oxyacid. Phenylbis- trifluororaethylphosphine can be hydrolysed with aqueous alkali to give fluoroform and phenylphosphonous acid. Di- phenyltrifluoromethylphosphine, on the other hand, cannot be hydrolysed by aqueous alkali, but reacts slowly with alco• holic potassium hydroxide to give fluoroform and diphenyl- phosphinic acid. The phosphines form a further series of new com• pounds by reaction with halogens. Phenylbistrifluoromethyl- phosphine reacts with iodine to form trifluoroiodomethane, but forms phenylbistrifluororaethyldibromophosphorane with bromine. This compound also gives phenyltrifluoromethyl• phosphinic acid on aqueous hydrolysis, as obtained in the case of phenyltrifluoromethyliodophosphine. Besides forming