Hydrido(carbene), hydrido(diazoalkane), aqua(carbene), and vinyl(carbene) complexes of osmium(II)

The five-coordinate compound [OsHCl(CO)(PiPr(3))(2)] (1) reacts with CH2N2 and other diazoalkanes RCHN2 (R = Ph, CO2Et, SiMe3) in ether or toluene at 25 degrees C to give instead of the expected insertion products [Os(CH2R)Cl (CO) (PiPr(3))(2)] the isomeric hydrido(carbene)osmium(II) complexes [OsHCl (=CHR)(CO)(PiPr(3))(2)] (2-5) in excellent yields. With Me3SiCHN2 as the su bstrate, the 1:1 adduct [OsHCl(N2CHSiMe3) (CO)(PiPr(3))(2)] (6) was detecte d at low temperature as an intermediate. The reactions of 1 with Ph2CN2 and Cl4C5N2 afford the hydrido(diazo-alkane)compounds [OsHCl(N2CR2)(CO)(PiPr(3 ))(2)] (7, 8), which are quite stable and do not eliminate N-2 to give the corresponding hydrido(carbene)metal derivatives. Treatment of 3 (R = Ph) wi th either HCl or HBF4/H2O leads to the cleavage of the Os-H bond and result s in the formation of [OsCl2(=CHPh)(CO)(PiPr(3))(2)] (10) and [OsCl(=CHPh)( OH2)(CO)(PiPr(3))(2)]BF4 (11), respectively. The vinyl compound [OsCl(CH = CHPh)(CO)(PiPr(3))(2)] (12) behaves similarly to 1 and affords the carbene complex [OsCl(CH = CHPh)(=CHPh)(CO)(PiPr(3))(2)] (13) upon treatment with P hCHN2. Compound 13 rearranges in solution at room temperature to give the p i-allyl complex [Os(eta(3)-PhCHCHCHPh)Cl(CO)(PiPr(3))(2)] (14) as the domin ating species, The crystal and molecular structures of 4, 5, 10, and 11 hav e been determined by X-ray crystallography.