Strong influence of structures around aluminum centers constructed in polyoxotungstates for catalytic oxidation of alcohols with dioxygen in water

Water-soluble aluminum-coordinated polyoxotungstates, Cs4[α-PW11{Al(OH2)}O39]·8H2O (Cs-1), [(CH3)4N]4[α-PW11{Al(OH2)}O39]·8H2O (TMA-1), K6Na[(A-PW9O34)2{W(OH)(OH2)}{Al(OH)(OH2)}{Al(μ-OH)(OH2)2}2]·19H2O (KNa-2), and K7[α2-P2W17{Al(OH2)}O61]·14H2O (K-3), were used as homogeneous catalysts or catalyst precursors for the oxidation of alcohols with 1 atm molecular oxygen in a water–alcohol biphasic medium. The catalytic activities and the stabilities of polyoxoanions were significantly affected by the structures around the aluminum sites constructed in the polyoxotungstates. In particular, polyoxoanion 1 exhibited high turnover numbers and high selectivities of the corresponding carbonyl products, and the molecular structure of 1 was remarkably stable for oxidations with long time intervals.

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► Alcohols were oxidized by Al-coordinated polyoxotungstates with dioxygen in water.
► The activities were affected by the structures around the aluminum sites in polyoxoanions.
► [PW11{Al(OH2)}O39]4− exhibited high turnover numbers with >99% selectivity.
► [PW11{Al(OH2)}O39]4− was remarkably stable for oxidations with long time intervals.