Triosmium clusters with ligands derived from αβ-unsaturated ketones. X-ray crystal structures of [Os3H(CO)10(cis-MeCCHCOMe)] and [Os3H(OH)(CO)9(PMe2Ph)]

Abstract

The compounds [Os₃H₂(CO)₁₀] and [Os₃(CO)₁₀(MeCN)₂] both react with the enones RCHCHCOMe (R = H, Me, or Ph) by metallation at the vinylic C–H groups to give compounds of type [Os₃H(CO)₁₀-(RC₄H₄O)], certain of which were also obtained from [Os₃H₂(CO)₁₀] and CHCCOMe. Three isomers of [Os₃H(CO)₁₀(C₄H₅O)] were isolated, containing CH₂CCOMe and cis- and trans-CHCHCOMe respectively. The most stable isomer, [Os₃H(CO)₁₀(cis-CHCHCOMe)], is decarbonylated at 130 °C to give [Os₃H(CO)₉(cis-CHCHCOMe)] and contains a linear Os₃ chain and a terminal hydride replaceable by Cl from CCl₄. The substituted compounds [Os₃H(CO)₁₀(cis-RCCHCOMe)](R = Me or Ph) have a different structure; crystals of the compound with R = Me are monoclinic, space group C2/c, with a= 17.377(2), b= 14.293(2), c= 16.476(2)Å, β= 91.79(3)°, and Z= 8. The structure was solved via the heavy-atom method and refined to R= 0.034 using 2 906 diffractometer data with l 1.5σ(l). The structure is based on that of [Os₃(CO)₁₂] with a chelating MeCCHCOMe ligand occupying an axial and an equatorial site. The bridging hydride is not replaced by Cl in CCl₄ solution. Unable to obtain good crystals of [Os₃H(CO)₁₀(cis-CHCHCOMe)], [Os₃H₂(CO)₉(PMe₂Ph)] was treated with CH₂CHCOMe in an attempt to obtain a PMe₂Ph-substituted derivative but instead [Os₃H(OH)(CO)₉(PMe₂Ph)], was obtained, the crystals of which are monoclinic, space group P2₁/n, with a= 17.535(2), b= 9.500(1), c= 14.326(2)Å, β= 101.86(1)°, and Z= 4. The structure was solved by the heavy-atom method and refined to R= 0.041 using 3 474 diffractometer data with l 1.5σ(l).