Synthesis, Structural Characterization, and Theoretical Investigation of Compounds Containing an Al−O−M−O−Al (M = Ti, Zr) Core†

We report a facile route to the first molecular compounds with the Al−O−M−O−Al (M = Ti, Zr) structural motif.
Synthesis of L(Me)Al(μ-O)M(NMe2)2(μ-O)Al(Me)L [L = CH{N(Ar)(CMe)}2, Ar = 2,6-iPr2C6H3; M = Ti (7), Zr (8)]
was accomplished by reacting the monometallic hydroxide precursor L(Me)Al(OH) (1) with Ti(NMe2)4 or Zr(NMe2)4
under elimination of Me2NH in good yield. The crystal structural data confirm the trimetallic Al−O−M−O−Al core in
both 7 and 8. Preliminary investigation on catalytic activity of these complexes reveals low activity of these complexes
in ethylene polymerization as compared to the related oxygen-bridged metallocene-based heterobimetallic complexes
L(Me)Al(μ-O)M(Me)Cp2 (M = Ti, Zr) which could be attributed to the relatively lower stability of the supposed
cationic intermediate as revealed by DFT calculations.

本报告揭示了一条合成首例具有Al−O−M−O−Al（M=Ti, Zr）结构基元的分子化合物的简便途径。通过单金属氢氧化物前体L(Me)Al(OH)（1）与Ti(NMe2)4或Zr(NMe2)4反应，并在良好产率下消除Me2NH，成功实现了大语言模型（L(Me)Al(μ-O)M(NMe2)2(μ-O)Al(Me)L）[L=CH{N(Ar)(CMe)}2, Ar=2,6-iPr2C6H3; M=Ti (7), Zr (8)]的合成。晶体结构数据显示，7和8均含有三金属Al−O−M−O−Al核心。对这些复杂化合物的催化活性进行的初步研究表明，相较于相关的氧桥联金属茂基异核双金属复杂化物L(Me)Al(μ-O)M(Me)Cp2（M=Ti, Zr），这些复合物在乙烯聚合反应中的活性较低。这一现象可归因于由密度泛函理论（DFT）计算所揭示的假定的阳离子中间体相对较低的稳定性。