Zirconium and hafnium complexes of the thio(bisphenolato) ligand: synthesis, structural characterization and testing as 1-hexene polymerization catalysts.

Thio(bisphenolato) complexes of the type [M-2(mu-tbop-kappa O-3,S,O)(2)Cl-4] [M= Zr 1, Hf 2 and tbop = 2,2'-thiobis{4-(1,1,3,3-tetramethyl-butyl)phenolate}] were prepared by HCl elimination from tbopH(2) and MCl4. Substitution of the chlorides in 1 and 2 by 2,6-diisopropylphenolato groups (dipp) generates new compounds [M-2(mu-tbop-kappa O-3,S,O)(2)(dipp)(4)] (M= Zr 3, Hf 4). The structures of 1-4 were confirmed by NMR spectroscopy; complexes 3 and 4 were further investigated by X-ray crystallography. These studies showed 1-4 to be dimers either in the solid state or in solution and to have metal centers adopting distorted octahedral geometry. However treatment of MCl4 with [Al-2(mu-OEt)(2)(tbop-kappa O-3,S,O)(2)] or [Al-2(mu-tbop-kappa O-3,S,O)(2)Me-2] gave heterotrinuclear complexes [M(tbop-kappa O-3,S,O)(2)=Cl-2(mu-AlX2)(2)] (M= Zr, X = Cl 5, X = Me 7 and M = Hf, X = Cl 6, X = Me 8) for which the single-crystal X-ray diffraction analysis showed zirconium and hafnium centers to have eight-coordinate dodecahedral geometry. Complexes 1-6 after activation with aluminium alkyls and supporting on MgCl2 showed a lack of activity in the ethene polymerization process and moderate activity towards 1-hexene producing high molecular weight atactic poly(1-hexenes).