Preparation and properties of the mixed trinuclear molybdenum–tungsten cluster ‘aqua ion’; [WMo ₂ (µ ₃ -O)(µ ₂ -O) ₃ (OH ₂ ) ₉ ] ⁴⁺

Reaction of K2[MoCl6](or MoCl4) with K2[WCl6] in HCI (2 M) at 80 °C for 1 h has led to the isolation and characterisation of the first hetero Mo–W trinuclear cluster ‘qua ion’; [WMo2(µ3-O)(µ2-O)3(OH2)9]4+; subsequent solution studies have shown that both redox properties and water substitution rates at the two molybdenum centres are significantly influenced by the presence of the remote tungsten atom.