Vanadium(V) phenolate complexes for ring opening homo- and co-polymerisation of [epsilon]-caprolactone, L-lactide and rac-lactide

The vanadyl complexes [VO(OtBu)L1] (1) and {[VO(OiPr)]2(m-p-L2p)} (2) {[VO(OR)]2(m-p-L2m)} (R ¼ iPr 3, tBu 4) have been prepared from [VO(OR)3] (R ¼ nPr, iPr or tBu) and the respective phenol, namely 2,20- ethylidenebis(4,6-di-tert-butylphenol) (L1H2) or a,a,a 0 ,a 0-tetra(3,5-di-tert-butyl-2-hydroxyphenyl–p/m-) xylene-para-tetraphenol (L2p/mH4). For comparative studies, the known complexes [VO(m-OnPr)L1]2 (I), [VOL3]2 (II) (L3 H3 ¼ 2,6-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-4-tert-butylphenol) were prepared. An imido complex {[VCl(Np-tolyl)(NCMe)]2(m-p-L2p)} (5) has been prepared following work-up from [V(Np-tolyl)Cl3], L2pH4 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 3-caprolactone, L-lactide or rac-lactide with and without solvent present. The co-polymerization of 3-caprolactone with L-lactide or rac-lactide afforded co-polymers with low lactide content; the reverse addition was ineffective.