Syntheses and characterization of zirconium and hafnium complexes of amido-fluorenyl ligands [(NBut)SiMe2CH2(C13H8)](2-) and [(NPri)SiMe2CH2(C13H8)](2-)

The reaction of (PrN)-N-1(H)SiMe2CH2Cl with two equivalents of fluorenyllithium in THF led to [(PrN)-N-1(H)SiMe2CH2(C13H8)]Li(THF) (1) in high yield. X-ray diffraction studies of 1 revealed a monomeric structure with an eta(2)-coordinated fluorenyl ligand. Lithiation followed by the treatment with zirconium or hafnium tetrachloride afforded the corresponding dichloro complexes [(eta(1)-NPr1)SiMe2CH2(eta(5)-C13H8)]ZrCl2 (2) and [(eta(1)-NPr1)SiMe2CH2(eta(5)-C13H8)]HfCl2 (3). These metal adducts were characterized by NMR spectroscopy, and in the case of 3 also by X-ray diffraction. Compound 3 shows a weak interaction between the formally 14-electron Hf center and the C-H of the isopropyl group. The dialkyl compound [(eta(1)-NBut)SiMe2CH2(eta(5)-C13H8)]Zr(CH2SiMe3)(2) (4) was prepared from Me3SiCH2MgCl and [(eta(1)-NBut)SiMe2CH2(eta(5)C(13)H(8))]ZrCl2. The NMR spectroscopic and X-ray data point to a fairly congested environment around the zirconium atom. In contrast to the -SiMe2- bridged analogs, the -SiMe2CH2- Linked amido-fluorenyl complex 4 features a relatively unstrained Ligand backbone with a close to ideal trigonal planar geometry at the amido nitrogen atom. (C) 1997 Elsevier Science S.A.