Acyl- und Alkylidenphosphane. XVI. (Dimethylaminomethyliden)- und (Diphenylmethyliden)phosphane

Acyl- and Alkylidenephosphines. XVI. (Dimethylaminomethylidene)- and (Diphenylmethylidene) phosphines Alkyl- or arylbis(trimethylsilyl)phosphines 1 (R = mesityl, C₉H₁₁ a ; (CH₃)₃C b ; C₆H₅ c ; CH₃ d ) react only very slowly with dimethylformamide 2 and benzophenone 4. After repeated addition of small amounts of solid sodium hydroxide, however, the reaction-time is shortened from several months to a few days. The reactions between 1 a or 1 b and 2 yield the (dimethylaminomethylidene)phosphines 3 a and 3 b ; from 1 a and 4 mesityl-(diphenylmethylidene)phosphine 5 a is obtained. The formation of the thermally labile phosphines 3 d and 5 c is proved by NMR spectroscopy; these compounds dimerize very fast to give 2,4-bis(dimethylamino)-1,3-dimethyl- 10 d and 1,2,2,3,4, 4-hexaphenyl-1,3-diphosphetane 15 c. Similarly the lithium trimethylsilylphosphides 6 a , 6 c and 6 e (R = (CH₃)₃Si) react with 2 or 4 to form 3 a and 5 c as well as (diphenylmethylidene)-trimethyl-silylphosphine 5 e .