The Formation of P(iii) Products From Phosphinamides With Silicon Hydrides

Two N,N-diethyl derivatives of phosphinamides in the 3-phospholene series were used as models to develop techniques for reduction to P(III) derivatives. The products from the reduction with HSiCl3 in the presence of pyridine depended on the molar ratio of the participants. A 1 : 1 : 1 amide-HSiCl3-pyridine mixture after 2 h in refluxing benzene provided the phosphinous chlorides in preparatively useful (55–65%) yield. A 1 : 1.5 : 1.5 mixture led to coupling at phosphorus to give the diphosphine, also in good yield (60–65%). The diphosphines also resulted from refluxing a 1 : 1 mixture of the amide with phenylsilane. However, heating a 2 : 1 amide–silane mixture at 100° gave only the product of deoxygenation (65%). A 1-benzylaminophosphetane oxide was also reduced successfully. The conditions with HSiCl3 and C6H5SiH3 were applied to a noncyclic phosphinamide (C6H5)2PO(NEt2); reaction rates were considerably slower than for the cyclic amides, but similar P(III) products were formed. 13C and 31P NMR spectra are reported for all new compounds.