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 pheny lacetylene, cyclohexylacetylene, and 1-(trimethylsilyl)-1,4-pentadiyne , in hexane at 60-degrees-C, to give the hydride-carbyne complexes OsH Cl2(CCH2R)(P-i-Pr3)2 (R = Ph (2), Cy (3), CH2C=CSiMe3 (4)). The molecu lar structure of complex 2 was determined by X-ray crystallography. Cr ystals of 2 are orthorhombic, space group P2(1)2(1)2(1), with unit cel l 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 u nique, 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 desc ribed as a distorted octahedron with the two triisopropylphosphine lig ands occupying the apical positions. The equatorial plane is formed by the carbyne and the hydride ligands mutually cis disposed and two chl orine atoms. The reaction of 1 with trimethylsilylacetylene leads to O sHCl2(CCH3)(P-i-Pr3)2 (5), suggesting that the key intermediates of th ese processes are dihydrogenvinylidene species of osmium(II). The hydr ide-vinylcarbyne complexes OsHCl2(CCH=CH(CH3)CH2CH3)(P-i-Pr3)2 (8), Os HCl2(CCH=CCH2CH2CH2CH2CH2)(P-i-Pr3)2(9), and OsHCl2(CCH=C(CH3)2)(P-i-P r3)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. Co mplexes 8 and 9 were formed via the hydroxycarbyne intermediates OsHCl 2(CCH2C(OH)(CH3)CH2CH3)(P-i-Pr3)2 (6) and OsHCl2(CCH2C(OH)CH2CH2CH2CH2 CH2)(P-i-Pr3)2 (7). The synthesis of the hydroxycarbyne OsHCl2(CCH2C(O H)Ph2)(P-i-Pr3)2 (10) is also reported.