Reaction of [Os4(µ-H)4(CO)12] with cyclohexa-1,3-diene via chemical activation: synthesis and structural characterisation of [Os4(µ-H)2(CO)10(η6-C6H6)] and [Os4(CO)9(η6-C6H6)(η4-C6H8)] and their interconversion

Abstract

The tetranuclear hydrido cluster [Os₄(µ-H)₄(CO)₁₂]1 has been activated by Me₃NO–MeCN to give a reactive intermediate [Os₄(µ-H)₄(CO)₁₀(MeCN)₂]2 which reacts further with cyclohexa-1,3-diene in CH₂Cl₂ under refluxing to produce new clusters including the benzene-co-ordinated compounds [Os₄(µ-H)₂(CO)₁₀(η⁶-C₆H₆)]5 and [Os₄(CO)₉(η⁶-C₆H₆)(η⁴-C₆H₈)]6. Structural analyses of 5 and 6 by X-ray diffraction have shown that the benzene ligand is co-ordinated to one metal atom in an η⁶ fashion, and the C₆H₈ ligand in 6 is also terminally bonded to one metal atom. Crystal data: 5, a= 8.209(1), b= 15.029(2), c= 16.453(2)Å, β= 89.90(1)° and Z= 4; 6, a= 15.614(2), b= 16.465(2), c= 18.010(2)Å, β= 89.42(2)° and Z= 8. Interconversion between compounds 5 and 6 has been observed. Reaction of 5 with cyclohexa-1,3-diene via Me₃NO-MeCN activation leads to the formation of 6, while thermal decomposition of 6 affords 5.