MIXED TETRANUCLEAR RHENIUM-RUTHENIUM COMPOUNDS FORMED BY CARBON SULFUR BOND-CLEAVAGE IN REACTIONS OF [RE2(PYS)2(CO)6] (PYS = PYRIDINE-2-THIONATE) WITH [RU3(CO)12] - CRYSTAL-STRUCTURES OF [RERU3(MU-4-S) (MU-C5H4N)-(CO)14] AND [RE2RU2(MU-4-S) (MU-C5H4N) (MU-PYS) (CO)13]

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(mu-4-S)(mu-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 mu-4-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(mu-4-S)(mu-C5H4N)(mu-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(mu-4-S)(mu-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.