Synthesis, structure and ethylene polymerisation behaviour ofvanadium(IV and V) complexes bearing chelating aryloxides

摘要

The reaction of [V(Np-tolyl)Cl_3] with the sulfur-bridged diphenol ligand 2,2'-thiobis(4,6-di-tert-butylphenol), {2,2'-S[4,6-(t-Bu)_2C_6H_20H]_2}(LSH_2)afforded the complexes [V(LS)_2] (1) and[VOCl_3(MeCN)_2][H_3Np-tolyl] (2). Complex 2 could also be prepared directly from [V(Np-tolyl)Cl_3] and`wet' acetonitrile. Reaction of [V(Np-tolyl)(0t-Bu)_3] with LSH_2afforded [V0(μ_2-0H)(LS)]_2 6(MeCN)(3), whilst reaction of [VO(On-Pr)_3] with 2,2'-sulfinylbis(4,6-di-tert-butylphenol),{2,2'-S0_2[4,6-(t-Bu)_2C_6H_2OH]_2}(LSO_2H_2),afforded [V(LS0_2)_2] MeCN (4). The reaction of[V0(0i-Pr)_3] with the ethylidene-bridged diphenol 2,2'-ethylidenebis(4,6-di-tert-butylphenol),{2,2'-CH_3CH[4,6-(t-Bu)_2C_6H_20H]_2}(LH2)afforded the hydroxyl bridged complexes [(VOL)_2(μ_2-0H)(μ_2-0i-Pr)](5)(major product) and [V0(μ_2-0H)(L)]_2.4(MeCN) (6) (minor product). Ingeneral, we find that controlled hydrolysis of [V(NAr)(0n-Pr)_3] (Ar = p-ClC_6H_4,p-OCNC_6H_4orp-tolyl) in the presence of LH_2reproducibly led to the vanadyl complex [V0(μ-0n-Pr)L]_2 2(MeCN) (7),in which the n-propoxide bridges both unexpectedly lie above the V202 plane. Reaction of the lineartriphenol 2,6-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-4-tert-butylphenol, [ArCH2Ar1 CH2Ar] (Ar =4,6-di-tert-butylphenol; Ar1 = 4-tert-butylphenol) (L~1H_3), and [VO(On-Pr),] afforded the complex[VOL~1]_2 3(MeCN) (8), whilst reaction of [V(Np-tolyl)(Oi-Pr)3] with the related methylene-bridgedlinear triphenol 2,6-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-4-methylphenol, [ArCH2Ar2CH2Ar] (L~2H_3)(Ar2 = 4-methylphenol), gave {[V(μ_2-0)(Np-tolyl)][V0(0i-Pr)]L~2}_2 1.5(MeCN) (9). The crystalstructures of 1 to 9 are reported. Complexes 1-4 and 7-9 were screened as pro-catalysts for thepolymerisation of ethylene in the presence of the co-catalyst dimethylaluminium chloride (DMAC) andthe re-activator ethyltrichloroacetate (ETA). All are highly active ethylene polymerisation catalysts withactivities covering the range 2000 to 90 000 g mmol-1 h-1 bar-1, and these results are discussed in termsof the ligands present at vanadium in the pro-catalyst. Complex 3 has also been screened forethylene/propylene copolymerisation.