SYNTHESIS OF NEW HYDRIDE-CARBYNE AND HYDRIDE-VINYLCARBYNE COMPLEXES OF OSMIUM(II) BY REACTION OF OSH2CL2(P-I-PR3)2 WITH TERMINAL ALKYNES

The dihydride-dichloro complex OsH2Cl2(P-i-Pr3)2 (1) reacts with phenylacetylene, cyclohexylacetylene, and 1-(trimethylsilyl)-1,4-pentadiyne, in hexane at 60-degrees-C, to give the hydride-carbyne complexes OsHCl2(CCH2R)(P-i-Pr3)2 (R = Ph (2), Cy (3), CH2C=CSiMe3 (4)). The molecular structure of complex 2 was determined by X-ray crystallography. Crystals of 2 are orthorhombic, space group P2(1)2(1)2(1), with unit cell dimensions a = 8.7490(3) angstrom, b = 15.4051(5) angstrom, and c = 22.4257(8) angstrom. The structure was solved and refined using 4615 unique, observed (F greater-than-or-equal-to 5.0sigma(F)) reflections; R = 0.022 and R(w) = 0.023. The geometry around the osmium can be described as a distorted octahedron with the two triisopropylphosphine ligands occupying the apical positions. The equatorial plane is formed by the carbyne and the hydride ligands mutually cis disposed and two chlorine atoms. The reaction of 1 with trimethylsilylacetylene leads to OsHCl2(CCH3)(P-i-Pr3)2 (5), suggesting that the key intermediates of these processes are dihydrogenvinylidene species of osmium(II). The hydride-vinylcarbyne complexes OsHCl2(CCH=CH(CH3)CH2CH3)(P-i-Pr3)2 (8), OsHCl2(CCH=CCH2CH2CH2CH2CH2)(P-i-Pr3)2(9), and OsHCl2(CCH=C(CH3)2)(P-i-Pr3)2 (11) were prepared by reaction of 1 with 3-methyl-1-pentyn-3-ol, 1-ethynyl-1-cyclohexanol, and 2-methyl-1-buten-3-yne, respectively. Complexes 8 and 9 were formed via the hydroxycarbyne intermediates OsHCl2(CCH2C(OH)(CH3)CH2CH3)(P-i-Pr3)2 (6) and OsHCl2(CCH2C(OH)CH2CH2CH2CH2CH2)(P-i-Pr3)2 (7). The synthesis of the hydroxycarbyne OsHCl2(CCH2C(OH)Ph2)(P-i-Pr3)2 (10) is also reported.