Coupling of carbon dioxide with neat propylene oxide catalyzed by aminebisphenolato cobalt(II)/(III) complexes and ionic co-catalysts

Cobalt complexes of tetradentate amine-phenolate ligands were studied for their potential in coupling carbon dioxide with propylene oxide under neat reaction conditions. Cobalt(II) complexes afforded catalytic systems with higher TONs than analogous cobalt(III) compounds. Tetrabutylammonium bromide (TBAB) and PPN+N3- were effective co-catalysts whereas N,N-dimethylaminopyridine (DMAP) shut down reactivity. Ligands containing a pendant pyridyl donor afforded more active catalysts than those containing dimethylamine groups. Reactions proceeded well at room temperature under moderate pressures of carbon dioxide. (C) 2011 Elsevier B.V. All rights reserved.