Mixed tetranuclear rhenium–ruthenium compounds formed by carbon–sulphur bond cleavage in reactions of [Re2(pyS)2(CO)6](pyS = pyridine-2-thionate) with [Ru3(CO)12]. Crystal structures of [ReRu3(µ4-S)(µ-C5H4N)(CO)14] and [Re2Ru2(µ-S)(µ-C5H4N)(µ-pyS)(CO)13]

Abstract

The dinuclear compound [Re₂(pyS)₂(CO)₆](pyS = pyridine-2-thionate) reacts with [Ru₃(CO)₁₂] to give a series of compounds containing ReRu₃, Re₂Ru₂, and Re₃Ru groups and which are formally built up by the combination of Re(pyS)(CO)₃ and Ru(CO)_x(x= 2, 3 or 4) units. The compound [ReRu₃(µ₄-S)(µ-C₅H₄N)(CO)₁₄] is formed by C–S bond cleavage and exists as two non-interconverting but inseparable isomers in solution. A single crystal selected from the crystallised mixture was found by X-ray structure determination to contain just one pure diastereomer as a mixture of enantiomers. The four metal atoms are linked by a µ₄-S ligand and a disordered 2-pyridyl ligand bridges two Ru(CO)₃ groups. The isomers in solution result from the interchange of Re(CO)₄ and Ru(CO)₄ units. Two non-interconvertible isomers of the compound [Re₂Ru₂(µ₄-S)(µ-C₅H₄N)(µ-pyS)(CO)₁₃] were separated and each structurally characterised. Their structures are extremely similar (except that one has CH₂Cl₂ molecules in the crystal) differing only in the orientation of the 2-pyridyl bridges. Full crystallographic characterisation depended upon the correct positioning of C and N atoms. The compound [Re₃Ru(µ₄-S)(µ-C₅H₄N)(pyS)₂(CO)₁₁] also forms separable non-interconverting isomers. One contains two doubly bridging pyS ligands and the other one doubly and one triply bridging pyS ligand. Therefore isomerism in these compounds has three separate origins.