[ML(N)(SIR(3))(ETA(2)-H-H)] OR [ML(N)(H)(ETA(2)-H-SIR(3))] - AN AB-INITIO MO STUDY ON [OSCL(CO)(PR(3))(2)''H(2)SIR(3)''] COMPLEXES

Ab initio MO calculations at the MP2 and MP4 levels on the [OsCl(CO)(P H3)(2)''H2SiH3''] model system predict the possible existence of two d ifferent stable species, one of [OsCl-(Co)(PH3) 2(SiH3)(eta(2)-H-H)] n ature and another of [OsCl(CO)(PH3)(2)(H)(eta(2)-H-SiH3)] nature, very close in. energy. From data on this particular system, the importance of different energy contributions for the relative stability of [ML(n )(SiR(3))(eta(2)-H-H)] and [ML(n)(H)(eta(2)-H-SiR(3))] complexes is an alyzed.