Aqueous Reduction of [Cp*2W2O5]: Characterization of the Triangular Clusters [Cp*3W3O4(OH)2]2+ and [Cp*3W3O6]+ – Comparison with Molybdenum

Zinc reduction of Cp*2W2O5 in an acidified water–methanol medium affords the green 3-electron trinuclear cluster [Cp*3W3O4(OH)2]2+, isolated and crystallographically characterized as the triflate salt, 1. Upon exposure to air, this complex is oxidized to a related 2-electron cluster, [Cp*3W3O6]+, which was crystallized and characterized in three different salts, 2–4. The 3-electron cluster exhibits a near-tetragonal frozen-glass EPR spectrum, and it shows evidence of coupling of the unpaired electron to only one of the three W atoms. The two-electron cluster is diamagnetic. An electrospray ionization MSn study revealed a stepwise expulsion of neutral [Cp*WO2] units as the main fragmentation process. DFT calculations unveiled the intimate details of the electronic structures of these complexes and fully rationalized the structural and spectroscopic properties.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)