1,2- and 1,3-diphosphetanes from alkylidenephosphines

Alkyl- or arylbis(trimethylsilyl)phosphines as well as tris(trimethylsilyl)phosphine and the corresponding arsines react with acyl chlorides to give [1-(trimethylsiloxy)alkylidene]phosphines 1 and -arsines 2; most of their 2,2-dimethylpropylidene derivatives are thermally stable at room temperature. With the same class of phosphines as starting compounds and carbon disulfide [bis(trimethylsilylsulfano)methylidene]phosphines 3 are formed, whereas [(dialkylamino)methylidene]-4 and [diarylmethylidene]phosphines 5 or the corresponding arsines 6 and 7 can be obtained from acyl amides or ketones

(Iminomethylidene)phosphines (RP=C=NR)

There has been much recent interest in compounds incorporating P=C 2,3 and P=P 4 double bonds. Furthermore, the stable (2,2-dimethylpropylidyne)phosphine, (CH 3)CC≡P, featuring a PC triple bond has been prepared.5 However, previous attempts to isolate cumulenes possessing a two-coordinate phosphorus atom, RP=C=X, have failed,2,3,6 except in a single case, the preparation of the stable and sterically protected (CH 3)CP=C=NC(CH 3h)-3. We now wish to report a general method of preparation of unstable (iminomethylidene)phosphines (monophosphorus analogues of carbodiimides), their direct observation by IR and mass spectrometry, and their initial chemical reactions