Application of Amine Elimination for the Efficient Preparation of Electrophilic ansa-Monocyclopentadienyl Group 4 Complexes Containing an Appended Amido Functionality. Structural Characterization of [(C5H4)SiMe2(N-t-Bu)]ZrCl2(NMe2H)
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Abstract
The homologous series of ansa-monocyclopentadienyl amido complexes [(C5H4)SiMe2(N-t-Bu)]M(NMe2)2 (M = Ti (2), Zr (3), Hf (4)) and [(C5Me4)SiMe2(N-t-Bu)]Zr(NMe2)2 (8) are prepared in 70−85% isolated yields by heating the neat 1:1 reaction mixture of (C5R4H)SiMe2(N(H)-t-Bu), where R = H, Me, and M(NMe2)4, at 110−120 °C for 24−48 h under a N2 purge. Whereas the reactions of 2 with 2 equiv of [NEt3H]Cl or HCl produce a mixture of [(C5H4)SiMe2(N-t-Bu)]TiCl2 (5) and [(C5H4)SiMe2Cl]TiCl2(NMe2)(NMe2H) (6), the reaction of 2 with SiMe3Cl in toluene provides a suitable route for the quantitative conversion of 2 to 5. Alternatively, the reactions of 3 and 8 with 2 equiv of [NEt3H]Cl or HCl afford solely the dimethylamine adduct [(C5H4)SiMe2(N-t-Bu)]ZrCl2(NMe2H) (7) and the dichloride derivative [(C5Me4)SiMe2(N-t-Bu)]ZrCl2 (1), respectively. Compounds 1−8 have been characterized in solution by NMR measurements, and the molecular structures of 2, 7, and 8 have been determined by X-ray crystallography. The M−N(appended amido) bond distances and Cp(centroid)−M−N bond angles in 2, 7, and 8 are 1.972(4), 2.055(5), 2.108(4) Å and 105.5, 101.1, 100.2°, respectively.
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