Reactions of Diphosphine-Stabilized Tetracobalt Carbonyl Clusters with −Si(OR)3-Functionalized Alkynes

Abstract

Short-bite ligand cluster stabilization is achieved in the tetrahedral clusters [Co4(μ-CO)3 (CO)7(μ-dppy)] (1a−c), obtained in high yields by reactions of [Co4(CO)12] with 1 equiv of the diphosphine ligands dppy, Ph2PCH2PPh2 (dppm), Ph2PNHPPh2 (dppa), or (Ph2P)2N(CH2)3Si(OEt)3 (dppaSi), respectively. The structure of 1a has been determined by X-ray diffraction, and the P atoms occupy axial positions on the basal face, transoid to a Co−Co bond. Clusters 1a−c were reacted with phenylacetylene to afford the corresponding butterfly clusters [Co4(μ-CO)2(CO)6(μ-dppy)(μ4-η2-PhC2H)] (2a−c) by insertion of the alkyne into a Co−Co bond of the precursor. This was established by an X-ray diffraction study of [Co4(μ-CO)2(CO)6(μ-dppm)(μ4-η2-PhC2H)] (2a). In an alternative synthetic procedure, the alkyne cluster [Co4(CO)10(μ4-η2-PhC2H)] (3), prepared from [Co4(CO)12] and phenylacetylene, was reacted with the diphosphines dppy. This led in good yields to butterfly clusters, isomeric with 2a−c in terms of the position of ...