Vanadium complexes with multidentate amine bisphenols

Abstract

The reaction of VO(acac)₂ (acac⁻ = acetyl acetonate) with tripodal glycine bisphenol H₃L¹ under an ambient atmosphere yields a hexacoordinated vanadium(IV) complex [V(acac)(L¹)] (1). The corresponding reactions with tripodal 2-propanolamine bisphenol H₃L² and potentially pentadentate ethoxyethanolamine bisphenol H₃L³ lead to the oxidation of the metal centre and formation of mononuclear oxovanadium(V) complexes [VO(L²)] (2) and [VO(L³)] (3), respectively. Alternatively, these latter two complexes can be prepared using VOSO₄·5H₂O or VO(OPr)₃ as a precursor. The CV of 1 in an ACN solution shows a reversible one-electron process at E_1/2 = +1.18 V, whereas 2 and 3 have an irreversible redox response at −1.6 V and −1.2 V, respectively. Complexes 2 and 3 show moderate activity in the epoxidation of cis-cyclooctene by tert-BuOOH at 50 °C.