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.