Oxidative addition of group 14 element hydrido compounds to OsH2(h2-CH2=CHEt)(CO)(PiPr3)2: Synthesis and characterization of the first trihydrido-silyl, trihydrido-germyl and trihydrido-stannyl derivatives of Os(IV)

The dihydrido−olefin complex OsH2(η2-CH2CHEt)(CO)(PiPr3)2 (2) reacts with H2SiPh2 to give OsH3(SiHPh2)(CO)(PiPr3)2 (3). The molecular structure of 3 has been determined by X-ray diffraction (monoclinic, space group P21/c with a = 16.375(2) Å, b = 11.670(1) Å, c =18.806(2) Å, β = 107.67(1)°, and Z = 4) together with ab initio calculations on the model compound OsH3(SiH3)(CO)(PH3)2. The coordination geometry around the osmium center can be rationalized as a heavily distorted pentagonal bipyramid with one hydrido ligand and the carbonyl group in the axial positions. The two other hydrido ligands lie in the equatorial plane, one between the phosphine ligands and the other between the SiHPh2 group and one of the phosphine ligands. Complex 3 can also be prepared by reaction of OsH(η2-H2BH2)(CO)(PiPr3)2 (4) with H2SiPh2. Similarly, the treatment of 4 with HSiPh3 affords OsH3(SiPh3)(CO)(PiPr3)2 (5), while the addition of H3SiPh to 4 in methanol yields OsH3{Si(OMe)2Ph}(CO)(PiPr3)2 (6). Complex 2 also reacts with HGeR3 and HSnR3 to give OsH3(GeR3)(CO)(PiPr3)2 (GeR3 = GeHPh2 (7), GePh3 (8), GeEt3 (9)) and OsH3(SnR3)(CO)(PiPr3)2 (R = Ph (10), nBu (11)), respectively. In solution, compounds 3 and 5−11 are fluxional and display similar 1H and 31P{1H} NMR spectra, suggesting that they possess a similar arrangement of ligands around the osmium atom.We thank the DGICYT (Projects PB92-0092, PB92-0621, and PB93-0222, Programa de Promoción General del Conocimiento) and the EU (Project: Selective Processes and Catalysis involving Small Molecules) for financial support. E.O. thanks the DGA (Diputación General de Aragón) for a grant.Peer reviewe