Synthesis, structural characterization, and theoretical investigation of compounds containing an Al-O-M-O-Al (M = Ti, Zr) Core

Abstract

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( mu- O) M( NMe2) 2( mu- O) Al( Me) L [ L) CH {N( Ar)( CMe)} 2, Ar) 2,6- i Pr2C6H3; 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( mu- O) M( Me) Cp-2 ( M) Ti, Zr) which could be attributed to the relatively lower stability of the supposed cationic intermediate as revealed by DFT calculations.