New salan and salen vanadium complexes: Syntheses and application in sulfoxidation catalysis

Publication date: 1 September 2018Source: Journal of Organometallic Chemistry, Volume 870Author(s): Minaxi S. Maru, Sónia Barroso, Pedro Adão, Luis G. Alves, Ana M. MartinsAbstractNew diamine bis-phenol compounds of salan- (HOPh’CHNH(CH2)2NHCHPh’OH, Ph’ = 2,4-(CMe2Ph)C6H2, H2L1) and salen-type (HOPh’’CHN(CHPh)2NCHPh’’OH, Ph’’ = 2,4-tBuC6H2, H2L2 and HOPh’’CHN(1,1′-2-binaphthyl)NCHPh’’OH, Ph’’ = 2,4-tBuC6H2, H2L3), as well as their oxido vanadium derivatives are described. VO(OiPr)3 was used as starting material for the preparation of [VO(OiPr)(L1)], 1, [VO(OiPr)(L2)], 3, and (μ-O){[VO(OiPr)(μ-O)(L3)VO]}2, 5. An intramolecular redox process involving the reduction of V(V) to V(IV) converts 3 into [VO(L2)], 4. The reactions of 1 and 5 with Me3SiCl give [VOCl(L1)], 2, and [VOCl(L3)], 6, respectively. All complexes were tested as catalysts for the sulfoxidation of thioanisole using H2O2 as oxidant. In general, the compounds display high activity and selectivity, although salan-type complexes (1 and 2) perform better. Comparison of complexes 5 and 6 shows that the monomeric species is more active and selective. Well-defined complexes, 5 and 6, display better catalytic performance than systems using 1:1.5 [VO(acac)2] and H2L3.Graphical abstractNew salan- and salen-vanadium complexes display high activity and selectivity in sulfoxidation of thioanisole. Salan-type complexes perform better. Well-defined binaphthyl-based salen complexes ...

Source: Journal of Organometallic Chemistry - July 11, 2018 Category: Chemistry Source Type: research