Six-coordinate aluminium cations: synthesis, characterization and catalysis

The present work details the synthesis and structural characterization of s ix-coordinate aluminium cations derived from the single starting material, Salen(Bu-t)AlCl 1 [Salen(Bu-t) = N,N'-ethylenebis(3,5-di-tert-butylsalicyli deneimine)]. They are of formula [Salen(Bu-t)Al(base)(2)]X-+(-) and contain various combinations of base and counter anion; H2O, Cl- 2, MeOH, Cl- 3, M eOH, BPh4- 4, MeOH, OTs- 5. With thf as base and OTs- as the anion, the neu tral complex, Salen(Bu-t)Al(thf)(OTs) 6 is obtained. MeOH can be added to 6 to displace the thf and produce 5. In contrast the addition of acetophenon e to 2 does not displace the H2O but produces the hydrogen-bonded complex 2 ... 2(acetophenone) 7. All of the compounds were characterized spectroscop ically and, in the case of 3, 5 and 7, by X-ray crystallography. Compounds 1-3 were examined for activity as oxirane polymerization catalysts.