STRUCTURAL AND COBALT-59 NUCLEAR-MAGNETIC-RESONANCE STUDY OF HETEROSITE REACTIVITIES OF ALKYNES IN RU-CO CARBONYL NITROSYL CLUSTERS

The reactions of tetetrahedral mixed-metal cluster [NEt4][RuCo3(CO)12] 1 with [NO][BF4] afforded the nitrosyl-substituted cluster [RuCo3(Co)11(NO)] 3 in high yield. The latter reacts with excess alkynes RC2R' to give [RuCo3(Co)9(NO)(mu-4-eta-2-RC=CR')](R = R' = Ph 4a; R = Ph, R' = H 4b; R = R' = H 4c) via specific insertion in a Co-Co bond, together with a small amount of the corresponding trinuclear cluster [RuCo2(CO)9(mu-3-eta-2-RC=CR')] (R = R' = Ph 5a; R = Ph, R' = H 5b; R = R' = H 5c). All the complexes have been characterised by IR, UV/VIS, H-1 and Co-59 NMR spectroscopy. The crystal structures of 3 and 4b have been determined by X-ray diffraction methods. Complex 3 exhibits a RuCo3 tetrahedron and the linear nitrosyl ligand is axially bonded to one of the Co atoms of the Co3 base. The structure of 4b consists of a RuCo3 butterfly in which the ruthenium atom occupies a hinge position, the alkyne ligand having been incorporated into the cluster core to generate a closo-RuCo3C2 octahedral framework.