Size-selective Catalysis of Ester and Anilide Cleavage by the Dinuclear Barium(II) Complexes of cis- and trans-Stilbenobis(18-crown-6)

The basic ethanolysis of esters and anilides endowed with a distal carboxylate anchoring group is catalyzed by the dinuclear Ba(II) complexes of cis- and trans-stilbenobis(18-crown-6). Comparison with the catalytic efficiency of a mononuclear model catalyst demonstrates that the two metal ions in the dinuclear complexes act synergically. The cis form of the catalyst is more efficient than the trans form and much more sensitive to the size of the substrate, showing that the concave shape imposed by the cis double bond is better suited for catalysis. An experiment in which the less active trans form is photoactivated in situ is also reported.