Synthesis, structures and catalytic properties of chelating N,N ′-bis(silylated) 1,2-benzenediamidozirconium(IV) chlorides [and a titanium(IV) analogue] and dimethylamides †

Abstract

Chelating diamido ligands of formula [C6H4{N(SiMe2X)}2-1,2]2−, abbreviated as L′2− (X = CHCH2) or L2− (X = Me), were used to prepare di(amido)metal(IV) chlorides [{M(Cl)L′(μ-Cl)(thf)}2] (M = Zr 2 or Ti 3), ZrCl2(L′) 5 and [ZrCl2(L)(tmen)] 6 and the heteroleptic amides [{Zr(NMe2)(Lx)(μ-NMe2)}2] (Lx = L′ 4 or L 7). Complexes 2 and 3 were obtained from equivalent proportions of Li2L′ (prepared in situ from H2L′ 1) and the appropriate metal chloride [MCl4(thf)2], while [Li2(L)(tmen)2] and ZrCl4 furnished 6. Treatment of Zr(NMe2)4 with an equivalent portion of H2L′ or H2L gave 4 and 7, respectively. Complex 5 was obtained from 4 and Si(Cl)Me3, and with thf yielded 2. The crystal structures of 2, 4, 6 and 7 have been determined. Compounds 2 and 4–6, unlike the less active titanium complex 3, were active catalysts with methylaluminoxane (AlMeO)n for polymerisation of ethene and the resulting polymers were shown to have extremely high average molecular weights, as determined by viscosity measurements.