Vanadium(v) phenolate complexes for ring opening homo- and co-polymerisation of ε-caprolactone, l-lactide and rac-lactide

Abstract

The vanadyl complexes [VO(OtBu)L¹] (1) and {[VO(OiPr)]₂(μ-p-L^2p)} (2) {[VO(OR)]₂(μ-p-L^2m)} (R = iPr 3, tBu 4) have been prepared from [VO(OR)₃] (R = nPr, iPr or tBu) and the respective phenol, namely 2,2′-ethylidenebis(4,6-di-tert-butylphenol) (L¹H₂) or α,α,α′,α′-tetra(3,5-di-tert-butyl-2-hydroxyphenyl–p/m-)xylene-para-tetraphenol (L^2p/mH₄). For comparative studies, the known complexes [VO(μ-OnPr)L¹]₂ (I), [VOL³]₂ (II) (L³H₃ = 2,6-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-4-tert-butylphenol) were prepared. An imido complex {[VCl(Np-tolyl)(NCMe)]₂(μ-p-L^2p)} (5) has been prepared following work-up from [V(Np-tolyl)Cl₃], L^2pH₄ and Et₃N. The molecular structures of complexes 1–5 are reported. Complexes 1–5 and I and II have been screened for their ability to ring open polymerise ε-caprolactone, L-lactide or rac-lactide with and without solvent present. The co-polymerization of ε-caprolactone with L-lactide or rac-lactide afforded co-polymers with low lactide content; the reverse addition was ineffective.