Structure and fluxional behaviour of µ-diphenylacetylene-closo-tetrakis(tricarbonylruthenium)(4 Ru–Ru)

Abstract

The X-ray structure determination of [Ru₄(CO)₁₂(C₂Ph₂)] confirms the previously proposed closo-Ru₄C₂ unit with the alkyne capping a butterfly arrangement of the four ruthenium atoms. Crystals are monoclinic, space group P2₁/c, Z= 4, a= 9.69(1), b= 16.88(2), c= 17.13(2)Å, β= 90.67(5)°; R 0.056 for 2 929 independent reflections. Variable-temperature ¹³C n.m.r. spectroscopy has enabled the activation energy and entropy to be measured for the mutual exchange of three carbonyl groups attached to one ruthenium, and also indicates that no exchange of carbonyls between different rutheniums occurs at <373 K.