An ab initio investigation of the relative stability of 1,3-di-phospha- 2-silaallenes (RP=Si=PR) with respect to potential isomers shows that the allene isomer is not the global mini-mum throughout a series of several substituents (R = H, SiH3 , CH3 , Ph, F) ? the siladiphosphirene isomer is significantly more stable for all these substituents. The stability of the di-phosphasilaallene relative to other isomers depends on the nature of the adjacent substituents. Thus, for simple carbon and silyl substituents alternative ring-closed isomers are fa-vored over the diphosphasilaallene, which, depending on the substituent, can show silylene or phosphasilene character. The results obtained at the DFT level are compared with those at other levels of theory for the parent system.
2006. 4570-4576 p.