Structure refinement from powder neutron diffraction data of Sn10W16O44, which contains a metal–metal bonded W6O12 cluster

Abstract

A powder neutron diffraction study of Sn^II₁₀W₁₆O₄₄ has shown that this is the correct composition for the compound previously assigned the formula Sn₁₀W₁₆O₄₆. The compound contains W₆O₁₂ clusters with 14 electrons 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 co-ordination of the W₆ unit to give the formulation of the cluster as W₆Oⁱ₁₂O^a₆. Two of these clusters are found in the unit cell, with the remaining four tungstens forming face-sharing octahedral W^VI₂O₉ units. The assignment of oxidation states and electron counting is supported by bond-valence calculations.