The tendency of tripodal amidozirconium and hafnium complexes to form hexacoordinate structures: alkali metal halide cages versus solvent adducts
摘要:
Reaction of the tripodal lithium amide [HC{SiMe2N(Li)(4-CH3C6H4)}(3)] with ZrCl4 in diethylether gave the chlorozirconium-lithum chloride complex [HC{SiMe2N(4-CH3C6H4)}(3)Zr{Cl-4(Li-OEt2)(3)}] (3). This contains a metal halide heterocubane unit fused to the tripodal amido cage through the hexacoordinate zirconium atom as established by an X-ray diffraction study. Recrystallisation of the compound in THF gives the hexacoordinate solvent adduct [HC{SiMe2N(4-CH3C6H4)}(3)ZrCl(THF)(2)] (4) which was also characterized by X-ray crystallography. Alkylation of the chloro complex [HC{SiMe2N(2-FC6H4)}(3)Zr((-Cl)(2)Li(OEt2)(2)] (2a) with methyllithium or t-butyllithium yields the alkylcomplexes [HC{SiMe2N(2-FC6H4)}(3)ZrCH3] (6) and [HC{SiMe2N(2-FC6H4)}(3)ZrC(CH3)(3)] (7) for which the JFH and JFC coupling with the metal-bound alkyl groups indicates involvement of the peripheral fluoro functions in the coordination to the metal centre. (C) 1999 Elsevier Science S.A. All rights reserved.