Dichlorosilylene Transfer to a P‐Fluorophosphaalkene: The Route to a C‐Dichlorofluorosilyl‐Functionalized Dialkyldiphosphene

Abstract

Reactions of the (trichlorosilyl)germane Me3GeSiCl3 and of the unsymmetric disilane Me3SiSiCl3 with the P‐fluorophosphaalkene (Me3Si)2C=PF (1) proceed with transfer of SiCl2 (2) leading to the new C‐dichlorofluorosilyl‐functionalized dialkyldiphosphene (Cl2FSi)(Me3Si)2CP=PC(SiCl2F)(SiMe3)2 (6), which was characterized by X‐ray crystallography. The P‐phosphanylphosphaalkene (Me3Si)2C=PP[C(SiCl2F)(SiMe3)2]SiCl2F (8a) was detected in the reaction mixtures by 31P NMR spectroscopy, accompanied by its isomer 8b, presumably (Cl2FSi)(Me3Si)C=PP[C(SiCl2F)(SiMe3)2]SiMe3. The unsymmetric dimers 8a and 8b rearrange by a 1,3‐(P→C) silyl group shift, providing the inversion‐symmetric diphosphene 6. Compound 6 was transformed with selenium into a selenadiphosphirane (9). Quantum chemical calculations were performed on intermediates on the route from 1 and 2 to the metastable unsymmetric dimers 8a and 8b. The addition of SiCl2 to the P=C bond of 1, followed by ring opening of the silaphosphirane 4, provides the phosphinidene (Me3Si)2(Cl2FSi)CP (5), which rearranges further to isomeric P‐silylphosphaalkenes (Me3Si)2C=PSiCl2F (7a) and (Cl2FSi)(Me3Si)C=PSiMe3 (7b). Rapid phosphinidene–phosphaalkene P–P coupling reactions of 5 with 7a and with 7b followed by 1,2‐(P→P) silyl group shift of ylide‐type dimers 11a and 11b explain the formation of the observed species 8a and 8b. The absence of species related to 8b in previous experiments on the reactions of the P‐chlorophosphaalkene (Me3Si)2C=PCl (1′) with Si2Cl6, with Me3GeSiCl3, and with Me3SiSiCl3, allows us to suggest that in the P‐chlorophosphaalkene case nucleophile‐supported SiCl2 insertion into the P–Cl bond or the substitutive Cl–/SiCl3– exchange are the preferred routes to the metastable P‐(trichlorosilyl)phosphaalkene (Me3Si)2C=PSiCl3.