Aromaticity of metal acetylacetonates and a Mobius chelate of a cadmium(II) complex of an N4 helical ligand
Abstract Interaction of a benzene C H tip with a metallacycle of various metal acetylacetonates are studied by means of DFT calculations at M062X/LanL2DZ and M062X/6 311++G(2d,p) levels. It is concluded that an angular interaction with a tilt angle th of the C H tip is diagnostic of aromaticity of a chelate ring in a metal acetylacetonate. Larger the th value, the more aromatic is the probed molecule. This finding is supported by the known X ray crystal structure of bis(acetylacetonato)platinum(II) benzene. Acetylacetonate anion has 6 p electrons fulfilling Huckel's 4n 2 rule for aromaticity. A thirteen membered 12 p electron chelate ring in a cadmium(II) complex of a helical N4 ligand is shown to be aromatic by establishing it as a Mobius object.