The reaction of the substrate [CpZr(CH2Ph)3] with the ligands 2,3,5,6-tetraphenyl- 1, 2-phenyl-4,6-di-tert-butyl- 2 or 2-(1-naphthyl)-4,6-di-tert-butyl-phenol 3 leads to the corresponding compounds [Cp(ArO)Zr(CH2Ph)2] 4â6. Solution studies show that naphthyl rotation is slow on the NMR timescale at ambient temperatures within 6 leading to non-equivalent benzyl groups with diastereotopic methylene protons. The solid-state structure of 5 shows both benzyl ligands to be η1-bound. Compounds 4â6 react with tert-butylisocyanide in hydrocarbon solvents to initially produce
the mono(iminoacyl) derivatives [Cp(ArO)Zr(η2-ButNCCH2Ph)(CH2Ph)] 7â9 followed by the bis(iminoacyl) products [Cp(ArO)Zr(η2-ButNCCH2Ph)2] 10â12. In the solution 13C NMR spectra of the iminoacyl derivatives the ZrâCN carbon atom resonates at δ 242â244 ppm (7â9) and δ 229â234 ppm (10â12) consistent with the η2-C,N binding. This was confirmed in the solid state by X-ray diffraction studies of 8, 11 and 12. At ambient temperatures only one set of iminoacyl
resonances are observed for 10 and 11, indicating that both iminoacyl rotation and aryloxide rotation are facile. At lower temperatures the iminoacyl ligands in 11 become non-equivalent in the 1H NMR spectrum consistent with restricted rotation about the ZrâOâAr bond. The iminoacyl ligands in the 2-(1-naphthyl) derivative 12 are non-equivalent in solution NMR spectra from â75 to +85 °C. The solution fluxionality of these molecules as determined by NMR studies is discussed in detail.
底物[CpZr(CH2Ph)3]与
配体 2,3,5,6-四苯基-1、2-苯基-4,6-二叔丁基-2 或 2-(1-
萘基)-4,6-二叔
丁基苯酚 3 反应生成相应的化合物[Cp(ArO)Zr(CH2Ph)2] 4â6。溶液研究表明,在 6 的环境温度下,
萘基旋转在核磁共振时间尺度上是缓慢的,从而导致具有非对映亚甲基质子的非等效苄基。5 的固态结构显示,两个苄基
配体都与δ-1 结合。化合物 4â6 在烃类溶剂中与
叔丁基异氰酸酯反应,首先生成单(亚
氨基酰基)衍
生物 [Cp(ArO)Zr(δ-2-ButNCCH2Ph)(CH2Ph)] 7â9 ,然后生成双(亚
氨基酰基)产物 [Cp(ArO)Zr(δ-2-ButNCCH2Ph)2]10â12。在亚
氨基酰基衍
生物的溶液 13C NMR 光谱中,ZrâCN 碳原子共振于 δ 242â244 ppm(7â9)和 δ 229â234 ppm(10â12),这与δ-2-C,N 结合一致。对 8、11 和 12 的 X 射线衍射研究证实了这一点。在常温下,10 和 11 只出现一组亚
氨基酰基共振,这表明亚
氨基酰基旋转和芳基氧基旋转都很容易。在较低温度下,11 中的亚
氨基酰
配体在 1H NMR 光谱中变得不等同,这与围绕 ZrâOâAr 键的旋转受限一致。2-(1-
萘基)衍
生物 12 中的亚
氨基
配体在 75 °C至 +85 °C的溶液核磁共振谱图中是非等价的。详细讨论了核磁共振研究确定的这些分子的溶液通性。