CO substitution in the mixed-metal clusters PhCCo₂Ni(CO)₆Cp and PhCCo₂Mo(CO)₈Cp by (Z)-Ph₂PCH=CHPPh₂. X-ray diffraction structures and proof of ligand bridging in PhCCo₂Ni(CO)₄[(Z)-Ph₂PCH=CHPPh₂]Cp and PhCCo₂Mo(CO)₆[(Z)-Ph₂PCH=CHPPh₂]Cp

Abstract

The heterometallic tetrahedrane clusters PhCCo₂Ni(CO)₆Cp (1) and PhCCo₂Mo(CO)₈Cp (3) react with the unsaturated diphosphine ligand (Z)-Ph₂PCH=CHPPh₂ at elevated temperature to afford the corresponding phosphine-substituted clusters PhCCo₂Ni(CO)₄[(Z)-Ph₂PCH=CHPPh₂]Cp (2) and PhCCo₂Mo(CO)₆[(Z)-Ph₂PCH=CHPPh₂]Cp (4). Clusters 2 and 4 have been isolated by column chromatography and characterized in solution by IR and NMR (¹H and ³¹P) spectroscopies, and the solid-state structures of these clusters have been determined by X-ray crystallography. PhCCo₂Ni(CO)₄[(Z)-Ph₂PCH=CHPPh₂]Cp crystallizes in the triclinic space group P-l, a = 10.8142(7), b = 10.8994(6), c = 17.661(2) Å, α = 82.870(6), β = 86.149(7), γ = 64.493(5)^∘, V = 1864.0(2) ų, Z = 2, D_cacl = 1.495 g/cm³; R = 0.0409, R_w = 0.0424 for 3147 observed reflections with I > 3σ(I). PhCCo₂Mo(CO)₆[(Z)-Ph₂PCH=CHPPh₂]Cp, as the hexane solvent, crystallizes in the monoclinic space group P2₁/c, a = 12.706(4), b = 17.367(3), c = 21.639(7) Å, β = 106.48(3)^∘, V = 4579(1) ų, Z = 4, D_cacl = 1.478 g/cm³; R = 0.0605, R_w = 0.0724 for 1330 observed reflections with I > 3σ(I). The solid-state structures of 2 and 4 confirm a bridging coordination mode for the (Z)-Ph₂PCH=CHPPh₂ ligand, with adjacent cobalt centers being ligated by the ancillary phosphine ligand. The structural highlights of these new mixed-metal clusters are discussed relative to the homometallic tetrahedrane cluster PhCCo₃(CO)₇[(Z)-Ph₂PCH=CHPPh₂].