THE TENDENCY OF TRIPODAL AMIDOZIRCONIUM AND HAFNIUM COMPLEXES TO FORM HEXACOORDINATE STRUCTURES : ALKALI METAL HALIDE CAGES VERSUS SOLVENT ADDUCTS

Abstract Reaction of the tripodal lithium amide [HC{SiMe 2 N(Li)(4-CH 3 C 6 H 4 )} 3 ] with ZrCl 4 in diethyl ether gave the chlorozirconium–lithum chloride complex [HC{SiMe 2 N(4-CH 3 C 6 H 4 )} 3 Zr{Cl 4 (LiOEt 2 ) 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{SiMe 2 N(4-CH 3 C 6 H 4 )} 3 ZrCl(THF) 2 ] ( 4 ) which was also characterized by X-ray crystallography. Alkylation of the chloro complex [HC{SiMe 2 N(2-FC 6 H 4 )} 3 Zr((-Cl) 2 Li(OEt 2 ) 2 ] ( 2a ) with methyllithium or t -butyllithium yields the alkylcomplexes [HC{SiMe 2 N(2-FC 6 H 4 )} 3 ZrCH 3 ] ( 6 ) and [HC{SiMe 2 N(2-FC 6 H 4 )} 3 ZrC(CH 3 ) 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.