Vanadium(v) tetra-phenolate complexes: synthesis, structural studies and ethylene homo-(co-) polymerization capability

Reaction of the ligand α,α,α′,α′-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-p-xylene (p-L1H4) with two equivalents of [VO(OR)3] (R = nPr, tBu) in refluxing toluene afforded, after work-up, the complexes {[VO(OnPr)(THF)]2(-p-L1)}·2(THF) (1·2(THF)) or {[VO(OtBu)]2(-p-L1)}·2MeCN (2·2MeCN), respectively in moderate to good yield. A similar reaction using the meta ligand, namely α,α,α′,α′-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-m-xylene (m-L2H4) afforded the complex {[VO(OnPr)(THF)]2(-p-L2)} (3). Use of [V(Np-R1C6H4)(tBuO)3] (R1 = Me, CF3) with p-L1H4 led to the isolation of the oxo-imido complexes {[VO(tBuO)][V(Np-R1C6H4)(tBuO)](-p-L1)} (R1 = Me, 4·CH2Cl2; CF3, 5·CH2Cl2), whereas use of [V(Np-R1C6H4)Cl3] (R1 = Me, CF3) in combination with Et3N/p-L1H4 or p-L1Na4 afforded the diimido complexes {[V(Np-MeC6H4)(THF)Cl]2(-p-L1)}·4toluene (6·4toluene) or {[V(Np-CF3C6H4)(THF)Cl]2(-p-L1)} (7). For comparative studies, the complex [(VO)(μ-OnPr)L3]2 (8) has also been prepared via the interaction of [VO(nPrO)3] and 2-(α-(2-hydroxy-3,5-di-tert-butylphenyl)benzyl)-4,6-di-tert-butylphenol (L3H2). The crystal structures of 1·2THF, 2·2MeCN, 3, 4·CH2Cl2, 5·CH2Cl2, 6·4toluene·thf, 7 and 8 have been determined. Complexes 1 – 3 and 5 - 8 have been screened as pre-catalysts for the polymerization of ethylene in the presence of a variety of co-catalysts (with and without a re-activator), including DMAC (dimethylaluminium chloride), DEAC (diethylaluminium chloride), EADC (ethylaluminium dichloride) and EASC (ethylaluminium sesquichloride) at various temperatures and for the co-polymerization of ethylene with propylene; results are compared versus the benchmark catalyst [VO(OEt)Cl2]. In some cases, activities as high as 243,400 g/mmolV.h (30.43 Kg PE/mmolV.h.bar) were achievable, whilst it also proved possible to obtain higher molecular weight polymers (in comparable yields to the use of [VO(OEt)Cl2]). In all cases with dimethylaluminium chloride (DMAC)/ethyltrichloroacetate (ETA) activation, the activities achieved surpassed those of the benchmark catalyst. In the case of the co-polymerization of ethylene with propylene, Complexes 1 – 3 and 5 - 8 showed comparable or higher molecular weight than [VO(OEt)Cl2] with comparable catalytic activities or higher in the case of the imido complexes 6 and 7

Vanadium(V) oxo and Imido calix[8]arene complexes: synthesis, structural studies, and ethylene homo/copolymerisation capability

Interaction of p-tert-butylcalix[8]areneH8 (L8H8) with [NaVO(OtBu)4] (formed in situ from VOCl3) afforded the complex [Na(NCMe)5][(VO)2L8H]·4 MeCN (1·4 MeCN). Increasing [NaVO(OtBu)4] to 4 equiv led to [Na(NCMe)6]2[(Na(VO)4L8)(Na(NCMe))3]2·10 MeCN (2·10 MeCN). With adventitious oxygen, reaction of 4 equiv of [VO(OtBu)3] with L8H8 afforded the alkali-metal-free complex [(VO)4L8(μ3-O)2] (3); solvates 3×3 MeCN and 3×3 CH2Cl2 were isolated. For the lithium analogue, the order of addition had to be reversed such that lithium tert-butoxide was added to L8H8 and then treated with 2 equiv of VOCl3; crystallisation afforded [(VO2)2Li6[L8](thf)2(OtBu)2(Et2O)2]·Et2O (4·Et2O). Upon extraction into acetonitrile, [Li(NCMe)4][(VO)2L8H]·8 MeCN (5·8 MeCN) was formed. Use of the imido precursors [V(NtBu)(OtBu)3] and [V(Np-tolyl)(OtBu)3] and L8H8, afforded [tBuNH3][{V(p-tolylN)}2L8H]·3 1/2 MeCN (6·3 1/2 MeCN). The molecular structures of 1 to 6 are reported. Complexes 1, 3, and 4 were screened as precatalysts for the polymerisation of ethylene in the presence of cocatalysts at various temperatures and for the copolymerisation of ethylene with propylene. Activities as high as 136 000 g (mmol(V) h)-1 were sometimes achieved; higher molecular weight polymers could be obtained versus the benchmark [VO(OEt)Cl2]. For copolymerisation, incorporation of propylene was 7.1-10.9 mol% (compare 10 mol% for [VO(OEt)Cl2]), although catalytic activities were lower than [VO(OEt)Cl2]

Tri- and tetra-dentate imine vanadyl complexes: synthesis, structure and ethylene polymerization/ring opening polymerization capability

A number of vanadyl complexes bearing tri- or tetradentate phenoxyimine ligands have been structurally characterized and shown to exhibit high catalytic activity for ethylene polymerization in the presence of diethylaluminium chloride and ethyltrichloroacetate; at high temperatures, such complexes were also capable of Q4 the ROP of ε-caprolactone

Vanadyl complexes bearing bi-dentate phenoxyimine ligands: synthesis, structural studies and ethylene polymerization capability

Vanadyl complexes bearing bi-dentate phenoxyimine ligands: synthesis, structural studies and ethylene polymerization capabilit