Selective Binding of the Keto Form of Acetylacetone by Cyclic Trimeric Perfluoro-<i>o</i>-phenylenemercury. Quantitative Shift of the Keto−Enol Equilibrium in Acetylacetone Toward Its Keto Form Stabilized by the Complexation

This paper reports on the remarkable ability of cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3 (1) to bind selectively the less stable keto form of acetylacetone (AA) with the formation of a sandwich complex {[(o-C6F4Hg)3]2(AA)} (2), wherein the molecule of AA is disposed between the mutually parallel planes of two macrocycles and is bonded to each of them via the cooperative coordination of its carbonyl oxygen atoms by all three Hg centers of the neighboring molecule of 1. The synthesized 2 is the first example of a structurally characterized complex containing the keto form of AA as a ligand.