New Route to Access an Acyl-Functionalized Phosphasilene and a Four-Membered Si-P-C-O Heterocycle.

An acyl-functionalized phosphasilene, LSi(CO tBu)P(SiMe3) (L=PhC(N tBu)2) was synthesized on a new route by the addition of tBuCOCl to the phosphinosilylene LSiP(SiMe3)2 and subsequent Me3SiCl elimination. DFT studies elucidated its molecular structure, the influence of the acyl group on UV/Vis transitions, and revealed the mechanism. The intermediate LSi(CO tBu)ClP(SiMe3)2, with a five-coordinate silicon center, was characterized by NMR spectroscopy and X-ray analysis. On the other hand, phosphasilene LSi(SiMe3)P(SiMe3) reacted with tBuCOCl by a [2+2] cycloaddition of the silicon-phosphorus double bond and the carbon-oxygen double bond in addition to Me3SiCl elimination, thereby affording the novel, fully characterized compound LSi(SiMe3)[PC( tBu)O] bearing a Si-P-C-O heterocycle with a phosphorus-carbon double bond. DFT studies suggest that two mechanisms occur simultaneously. [ABSTRACT FROM AUTHOR]