Carbide forming and cluster build-up reactions in ruthenium carbonyl cluster chemistry

Abstract

The reinvestigation of an early synthesis of hexaruthenium carbido clusters has lead to the isolation of a number of new clusters which have been fully characterised by spectroscopic and crystallographic techniques. The thermolysis of Ru 3(CO) 12 in the presence of mesitylene (1,3,5-trimethylbenzene) at moderate temperatures yields two new clusters, [Ru 6(μ 4-η 2-CO) 2(CO) 13(η 6-C 6H 3Me 3)] (I) and [HRu 6(μ 4-η 2-CO)(CO) 13(μ 2-η 7-C 6H 3Me 2CH 2)] (II), the structures and reactivity of which indicate the origin and mechanism of formation of the carbido-carbon in the hexaruthenium carbido clusters [Ru 6C(CO) 14(η 6-C 6H 3Me 3)] (III) and [Ru 6C(CO) 17] (IV). A further product of the reaction is the decaruthenium carbido cluster dianion [Ru 10C(CO) 24] 2− (V) which has the tetracapped octahedral geometry. The monohydrido-cluster anion [HRu 10C(CO) 24] − (VI) may be synthesised quantitatively from V by protonation. The nature of the hydrido-ligand in VI has been investigated in the solid state by NMR spectroscopy and it has been found to be fluxional, its location being temperature dependent. The decanuclear dianion V has been found to react with mercury salts to yield the 21 metal atom cluster dianion [Ru 18Hg 3C 2(CO) 42] 2− (VII) which consists of two tricapped octahedral nonaruthenium “subclusters” fused by a bi-facecapping (Hg 3) 2+ unit.