OXIDATIVE ADDITION OF GROUP-14 ELEMENT HYDRIDO COMPOUNDS TO OSH2(ETA(2)-CH2=CHET)-(CO)(P(I)PR3)(2) - SYNTHESIS AND CHARACTERIZATION OF THE FIRST TRIHYDRIDO-SILYL, TRIHYDRIDO-GERMYL, AND TRIHYDRIDO-STANNYL DERIVATIVES OF OSMIUM(IV)

The dihydrido-olefin complex OsH2(eta(2)-CH2=CHEt)(CO)((PPr3)-Pr-i)(2) (2) reacts with H(2)SiPh(2) to give OsH3(SiHPh(2))(CO)((PPr3)-Pr-i)(2 ) (3). The molecular structure of 3 has been determined by X-ray diffr action (monoclinic, space group P2(1)/c with a = 16.375(2) Angstrom, b = 11.670(1) Angstrom, c = 18.806(2) Angstrom, beta = 107.67(1)degrees , and Z = 4) together with ab initio calculations on the model compoun d OsH3(SiH3)(CO)(PH3)(2). The coordination geometry around the osmium center can be rationalized as a heavily distorted pentagonal bipyramid with one hydride ligand and the carbonyl group in the axial positions . The two other hydride ligands lie in the equatorial plane, one betwe en the phosphine ligands and the other between the SiHPh(2) group and one of the phosphine ligands. Complex 3 can also be prepared by reacti on of OsH(eta(2)-H2BH2)(CO)((PPr3)-Pr-i)(2) (4) With H(2)SiPh(2). Simi larly, the treatment of 3 with HSiPh(3) affords OsH3(SiPh(3))(CO)((PPr 3)-Pr-i)(2) (5), while the addition of H(3)SiPh to 4 in methanol yield s OsH3{Si(OMe)(2)Ph}(CO)((PPr3)-Pr-i)(2) (6). Complex 2 also reacts wi th HGeR(3) and HSnR(3) to give OsH3(GeR(3))(CO)((PPr3)-Pr-i)(2) (GeR(3 ) = GeHPh(2) (7), GePh(3) (8), GeEt(3) (9)) and OsH3(SnR(3))(CO)((PP3) -P-i)(2) (R = Ph (10), (n)Bu (11)), respectively. In solution, compoun ds 3 and 5-11 are fluxional and display similar H-1 and P-31{H-1} NMR spectra, suggesting that they possess a similar arrangement of ligands around the osmium atom.