SOLUTION STUDIES ON THE TRIANGULAR INCOMPLETE CUBOIDAL DIMOLYBDENUM TUNGSTEN CLUSTER AQUA ION [MO2W(MU-3-O)-(MU-O)3(OH2)9]4+ - CRYSTAL-STRUCTURE OF [NME4]5[MO2W-(MU-O)(MU-O)3(NCS)9].C6H5ME

The synthesis and structural characterisation of the triangular incomplete cuboidal dimolybdenum-tungsten cluster aqua ion [Mo2W(mu3-O)(mu-O)3(OH2)9]4+ is reported. An X-ray crystallographic study of the derivative complex [NMe4]5[Mo2W(mu3-O)(mu-0)3(NCS)9].C6H5Me shows positional disorder at the Mo and W atoms resulting in crystallographically identical metal sites 2/3 Mo and 1/3 W in character. Oxygen-17 and molybdenum-95 NMR measurements coupled with redox studies have verified the presence of the mixed cluster in solution. A kinetic study with regard to 1 : 1 NCS- substitution at the water ligands is supportive of reaction occurring at one of the two more labile and statistically identical and independent molybdenum sites promoted through a conjugate base form presumed to derive via deprotonation of a water ligand trans to the mu-0 groups on the same molybdenum atom. Electronic effects on the redox ana substitution behaviour at molybdenum arising from the presence of the remote tungsten atom have been detected.