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)(L^x)(μ-NMe₂)}₂] (L^x = 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.

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