Dichlorosilylene and dichlorogermylene transfer to alkylidenephosphanes

The detection of Me3GeSiCl3, a product from the Si2Cl6 cleavage of trimethylgermylphosphanes, as a useful new source of SiCl2 moieties, as well as new trapping reactions of SiCl2 and GeCl2 with functional alkylidenephosphanes (Me3Si)2CPX (X = halide or dialkylphosphanyl [PRR′; R = i-propyl, R′ = t-butyl]) are reviewed. In the primary step of the reactions, insertion into the P–X bond is competing with addition to the PC bond. SiCl2 and GeCl2 insertions are followed by dimerisation reactions leading to new highly functional P-phosphanylalkylidenephosphanes, that may rearrange to diphosphenes like (XCl2Si)(Me3Si)2C–PP–C(SiMe3)2SiCl2X (X = F, Cl, P-i-Pr2) or (Cl3Ge)(Me3Si)2C–PP–C(SiMe3)2GeCl2PRR′ or/and react further with SiCl2 or GeCl2. Reaction of (Me3Si)2CP-PRR′ (R = i-propyl, R′ = t-butyl) with Me3GeSiCl3 leads in a very selective fashion to a complete PC double bond cleavage by unique double SiCl2 addition with formation of a stable P-phosphanylphosphadisiletane.