The preparation and hydrolysis of tertiary alkyl(perfluoroalkyl)phosphines

Abstract

The phosphines R(R_F)₂P (R_F= CF₃, R = Me, Buⁿ, Buⁱ, Ph; R_F= C₃F₇, R = Buⁿ, Ph) and Bu₂ⁿ(CF₃)P, and the phosphinous chloride Bu(CF₃)PCl, have been made from the chlorides (R_F)₂PCl or R_FPCl₂ and organolithium compounds in ether–hexane at –78°. The phosphines R₂(C₃F₇)P (R = Et, Ph, CF₃) and CF₃(C₃F₇)₂P have been made from the compounds R₂PCl or CF₃PCl₂ and heptafluoropropyl-lithium. The phosphine (CF₃)₂(C₃F₇)P was oxidised by nitrogen dioxide to the phosphine oxide (CF₃)₂(C₃F₇)PO, which was hydrolysed by water. Infrared and n.m.r. spectra are discussed. The hydrolyses of the compounds R(CF₃)₂P with alkali in water–ethanol follow second-order kinetics, and rate constants at 25° decrease in the order R = Buⁿ > Buⁱ > Ph. CF₃ was cleaved more easily than C₃F₇ from the unsymmetrical phosphine (CF₃)₂(C₃F₇)P, but from the phosphine oxide (CF₃)₂(C₃F₇)PO and from perfluoroalkyl phosphonites and phosphinates, the rate of cleavage of CF₃ was similar to that of C₃F₇.