The non-occurrence of the tristrifluoromethylphosphine complex and the production of mainly trans isomers of the above-mentioned phosphines has been interpreted in terms of steric phenomenon. Except dimethyltrifluoromethylphosphine, which forms mainly a cis isomer, the other phosphines, CH₃(CF₃)₂P,C₆H₅(CF₃)₂P, and (C₆H₅)₂ CF₃P form mainly trans isomers. A complex with tristrifluoromethylphosphine could not be obtained. The phosphines containing up to two trifluoromethyl groups form complexes with platinum(II) chloride. The phenyl-trifluoromethyl-phosphines form more stable complexes than the methyl-trifluoromethyl-phosphines. The phosphines containing more than one CF₃ group do not form addition compounds with boron trifluoride. In general, phosphines containing one trifluoromethyl group show similar properties to those of their parent compounds, trimethylphosphine and triphenylphosphine, while those containing two trifluoromethyl groups are very similar in their behaviour to tristrifluoromethylphosphine. By reaction with methyl iodide, this phosphine also forms a new phosphonium compound, methyldiphenyltrifluoromethylphosphonium iodide, which is readily hydrolysed by cold water with the loss of the trifluoromethyl group. It is interesting to note that diphenyltrifluoromethylphosphine is difficult to hydrolyse, whereas the phosphoranes can be hydrolysed easily, giving fluoroform and diphenylphosphinic acid. Besides forming the dibromophosphorane, diphenyltrifluoromethylphosphine is the first trifluoromethyl-phosphine known to form a diiodophosphorane. This compound also gives phenyltrifluoromethylphosphinic acid on aqueous hydrolysis, as obtained in the case of phenyltrifluoromethyliodophosphine. Phenylbistrifluoromethylphosphine reacts with iodine to form trifluoroiodomethane, but forms phenylbistrifluoromethyldibromophosphorane with bromine.
SPL 1070M PARTS SERIES
The phosphines form a further series of new compounds by reaction with halogens. Diphenyltrifluoromethylphosphine, on the other hand, cannot be hydrolysed by aqueous alkali, but reacts slowly with alcoholic potassium hydroxide to give fluoroform and diphenylphosphinic acid. Phenylbis-trifluoromethylphosphine can be hydrolysed with aqueous alkali to give fluoroform and phenylphosphonous acid. They are stable in air and cannot be hydrolysed with acid or water, except the iodophosphine C₆H₅CF₃PI, which reacts with water to give phenyltrifluoromethylphosphinic acid, a new oxyacid.
These new phosphines are colorless liquids (except phenyltrifluoromethyliodophosphine which is reddish-brown) of high boiling point. The latter has also been prepared by reaction of trifluoroiodomethane with either triphenylphosphine or diphenylchlorophosphine. Thus, a reaction with tetraphenylcyclotetraphosphine gives phenylbistrifluoromethylphosphine and phenyltrifluoromethyl-iodophosphine, and reaction with tetraphenyldiphosphine gives diphenyltrifluoromethylphosphine. The phenyl-trifluoromethyl-phosphines have been prepared by reacting trifluoroiodo-methane with a phosphorus compound containing a P-P bond. The reported methods for preparing the methyl-trifluoromethyl-phosphines do not produce a good yield therefore, an attempt has been made towards a better understanding of the reactions.
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.
For this purpose, substituted phosphines containing methyl or phenyl and trifluoromethyl groups have been prepared. This investigation has been concerned with the chemistry of some phosphines containing this group. One particular aspect of the chemistry of the trifluoromethyl group is its high electron-withdrawing power which reduces the donor properties of normally strong bases.
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