Structural and cobalt-59 nuclear magnetic resonance study of heterosite reactivities of alkynes in Ru–Co carbonyl–nitrosyl clusters

Abstract

The reactions of the tetrahedral 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)(µ₄-η²-RCCR′)](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(µ₃-η²-RCCR′)](R = R′= Ph 5a; R = Ph, R′= H 5b; R = R′= H 5c). All the complexes have been characterised by IR, UV/VIS, ¹H and ⁵⁹Co 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.