烷基铝络合的锆氢化合物：通过核磁共振光谱法鉴定氢化物桥连物种。

Alkylaluminum-complexed zirconocene hydrides: identification of hydride-bridged species by NMR spectroscopy.

作者信息

Baldwin Steven M, Bercaw John E, Brintzinger Hans H

机构信息

Arnold and Mabel Beckman Laboratories of Chemical Synthesis, California Institute of Technology, Pasadena, California 91125, USA.

出版信息

J Am Chem Soc. 2008 Dec 24;130(51):17423-33. doi: 10.1021/ja8054723.

DOI:10.1021/ja8054723

PMID:19032092

Abstract

Reactions of unbridged zirconocene dichlorides, (R(n)C(5)H(5-n))(2)ZrCl(2) (n = 0, 1, or 2), with diisobutylaluminum hydride (HAl(i)Bu(2)) result in the formation of tetranuclear trihydride clusters of the type (R(n)C(5)H(5-n))(2)Zr(mu-H)(3)(Al(i)Bu(2))(3)(mu-Cl)(2), which contain three [Al(i)Bu(2)] units. Ring-bridged ansa-zirconocene dichlorides, Me(2)E(R(n)C(5)H(4-n))(2)ZrCl(2) with E = C or Si, on the other hand, are found to form binuclear dihydride complexes of the type Me(2)E(R(n)C(5)H(4-n))(2)Zr(Cl)(mu-H)(2)Al(i)Bu(2) with only one [Al(i)Bu(2)] unit. The dichotomy between unbridged and bridged zirconocene derivatives with regard to tetranuclear versus binuclear product formation is proposed to be connected to different degrees of rotational freedom of their C(5)-ring ligands. Alkylaluminum-complexed zirconocene dihydrides, previously observed in zirconocene-based precatalyst systems activated by methylalumoxane (MAO) upon addition of HAl(i)Bu(2) or Al(i)Bu(3), are proposed to be species of the type Me(2)Si(ind)(2)Zr(Me)(mu-H)(2)Al(i)Bu(2), stabilized by interaction of their terminal Me group with a Lewis acidic site of MAO.

摘要

非桥连二氯锆茂，(R(n)C(5)H(5 - n))(2)ZrCl(2)（n = 0、1或2），与二异丁基氢化铝（HAl(i)Bu(2)）反应生成(R(n)C(5)H(5 - n))(2)Zr(mu - H)(3)(Al(i)Bu(2))(3)(mu - Cl)(2)类型的四核三氢簇合物，其包含三个[Al(i)Bu(2)]单元。另一方面，发现具有E = C或Si的环桥连ansa - 二氯锆茂Me(2)E(R(n)C(5)H(4 - n))(2)ZrCl(2)形成仅含一个[Al(i)Bu(2)]单元的Me(2)E(R(n)C(5)H(4 - n))(2)Zr(Cl)(mu - H)(2)Al(i)Bu(2)类型的双核二氢配合物。非桥连和桥连锆茂衍生物在四核与双核产物形成方面的二分法被认为与它们C(5) - 环配体的不同旋转自由度有关。先前在由甲基铝氧烷（MAO）活化的锆茂基预催化剂体系中，在加入HAl(i)Bu(2)或Al(i)Bu(3)后观察到的烷基铝络合锆茂二氢化物，被认为是Me(2)Si(ind)(2)Zr(Me)(mu - H)(2)Al(i)Bu(2)类型的物种，通过其末端甲基与MAO的路易斯酸性位点相互作用而稳定。