Catalytic Oxidation of Aliphatic Alcohols by Graphene Oxide Supported Binuclear Dioxidovanadium (V) Complexes.

Two new oxidovanadium(IV) complexes [CH2{VIVO(sal-sc)}2]·SO4 (1) and [CH2{VIVO(sal-tc)}2]·SO4 (2) and dioxidovanadium(V) complexes K2[CH2{VVO2(sal-sc)}2] (3) and K2[CH2{VVO2(sal-tc)}2] (4) were synthesised. Thoroughly characterized dioxidovanadium(V) complexes 3 and 4 were covalently grafted on the nano-surface of graphene oxide and heterogeneous catalysts GO-[CH2{VVO2(sal-sc)}2] (5) and GO-[CH2{VVO2(sal-tc)}2] (6) were isolated. Both the supported catalysts 5–6 efficiently catalyzed a series of straight-chain primary aliphatic alcohols and cyclic secondary aliphatic alcohols in the presence of H2O2 without any additional solvent. Straight-chain primary alcohols show better reactivity than cyclic secondary alcohols. Moreover, the alcohols with fewer carbon atoms are more reactive, and reactivity decreases with increasing carbon chain length of the alcohols. With 96% and 92% substrate conversion in the presence of 5 and 6, respectively, ethanol showing the highest reactivity among the examined alcohols. All the listed primary aliphatic alcohols exhibit more than 65% substrate conversion. Irrespective of the substrate 5 shows better performance than 6. The catalytic reaction proceeds through a radical mechanism wherein the in situ generated reactive species CH2{VVO(O)2(sal-sc)}2].MeOH detected through HR-MS analysis is believed to be the active component responsible for the oxidation of the alcohols. [ABSTRACT FROM AUTHOR]