Aluminum complexes of sterically hindered tetradentate Schiff bases: Synthesis, structure, and reactivity toward epsilon-caprolactone

The sterically hindered Schiff bases tbmSalenH(2) [tbmSalen = N,N'-1,2-ethylenebis(3-tert-butyl-5-methylsalicylideneimine)} and tbmSalcenH(2) [tbmSalcen - N,N'-trans-1,2-cyclohexanediyl-bis(3-tert-butyl-5-methylsalicylideneimine)] afforded a series of aluminum complexes of the general formulae [Al(tbmSalen)X] and [Al(tbmSalen)X] and [Al(tbmSalcen)X] (X = Cl, Me, Et). The molecular structure of [Al(tbmSalcen)Cl] was determined by single-crystal X-ray structural analysis which revealed a five-coordinate aluminum center with a distorted square pyramidal geometry. The alkyl complexes were found to oligomerize epsilon-caprolactone. (C) 1997 Elsevier Science S.A.