Formation mechanism of head-to-head amidato-bridged acetonylplatinum(III) binuclear complexes - Kinetic evidence for π-coordination of the enol form of a ketone in a ligand substitution reaction

Reactions of head-to-head (HH) α-pyridonato- and pivalamidato-bridged platinum(III) binuclear complexes withacetone were investigated kinetically. The reactions with acetone proceeded slowly to form acetonyl Pt^III binuclear complexes in two steps. A mechanism, which involves π-coordination of the enol form of acetone in the first step, followed by the π-β bond conversion in the second step, is proposed. π-Coordination of the enol was strongly supported by kinetic analyses of a ligand substitution reaction involving the pivalamidato-bridged Pt^III binuclear complex with (4-hydroxyphenyl)pyruvic acid. Only the enol form was reactive towards the Pt^III dimer complex. The enol form of acetone coordinates to the Pt(N₂O₂) atom in the HH amidato-bridged platinum(III) binuclear complex atfirst, and then the π-coordinated acetone changes to the β-coordinated acetone to form the acetonyl Pt^III binuclear complex.