STRUCTURE REFINEMENT FROM POWDER NEUTRON-DIFFRACTION DATA OF SN10W16O44' WHICH CONTAINS A METAL-METAL BONDED W6O12 CLUSTER

A powder neutron diffraction study of (Sn10W16O44)-W-II has shown that this is the correct composition for the compound previously assigned the formula Sn10W15O46. The compound contains W6O12 clusters with 14 e lectrons available for metal-metal bonding. This-electron count is in agreement with-the values found for octahedral Nb6O12 units in related niobates. Six apical oxygens complete the coordination of the W-6 uni t to give the formulation of the cluster as (W6O12O6a)-O-i. Two of the se clusters are found in the unit cell, with the remaining four tungst ens forming face-sharing octahedral (W2O9)-O-VI units. assignment of o xidation states and electron counting is supported by bond-valence cal culations.