Struktur und Farbigkeit von P,P′-Tetra-t-butyl-und P,P′-Tetraphenyl-oxalsäurediphosphid und Derivaten

The unexpected violet colour of P,P-tetraphenyl-oxalic acid diphosphide (3) stimulated the synthesis of the following derivatives: P,P-tetra-t-butyl-oxalic acid diphosphide (2), N,P-tetraphenyl-oxalic acid amide phosphide (4) and P, -triphenyl-glyoxylic acid phosphide (5). The compounds could be prepared by the reaction of the corresponding acyl chlorides with diorganyl-(trimethylsilyl) phosphine; (organyl=t-butyl and phenyl). The electronic transitions of green-blue2 and red5 in the 450–700 nm region are discussed, also theirv C=O in the ir spectrum. These results are interpreted in connection with the molecule structures of2 and3 which have been determined by X-ray crystal structure analysis. In2 the framework P–C(O)–C(O)–P is only slightly distorted from a coplanartrans-position, in3 somewhat more. The bonds at P have the expected pyramidal arrangement. The direction of the lone pairs at the P-atoms, derived from this bond arrangement, is discussed with respect to the electronic transitions in acyl phosphides.