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

The vanadyl complexes [VO(OtBu)L] (1) and {[VO(OiPr)](μ-p-L)} (2) {[VO(OR)](μ-p-L)} (R = iPr 3, tBu 4) have been prepared from [VO(OR)] (R = nPr, iPr or tBu) and the respective phenol, namely 2,2′-ethylidenebis(4,6-di-tert-butylphenol) (LH) or α,α,α′,α′-tetra(3,5-di-tert-butyl-2-hydroxyphenyl-p/m-)xylene-para-tetraphenol (LH). For comparative studies, the known complexes [VO(μ-OnPr)L] (I), [VOL] (II) (LH = 2,6-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-4-tert-butylphenol) were prepared. An imido complex {[VCl(Np-tolyl)(NCMe)](μ-p-L)} (5) has been prepared following work-up from [V(Np-tolyl)Cl], LH and EtN. 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.