Studies on the Reacions of Bis(acetylacetonato)platinum(II) with Lewis Bases. II. Reaction with Pyridine Leading to Complexes Containing Uni- and Bis-Carbon Bonded Acetylacetonato Ligand(s).

Heating a pyridine solution of [Pt(acac)2] (acac=2,4-pentanedionato-O,O′) at 100°C afforded central C-bonded complexes, [Pt(acac)(γ-acac)py], 1, and [Pt(γ-acac)2py2], 2 (γ-acac=2,4-pentanedionato-C3). Complexes 1 and 2 were isolated and characterized by means of elemental analysis, infrared and 1H- and 13C-NMR spectroscopy. Heating 1 in pyridine yielded 2, and conversely, heating 2 in CDCl3 yielded 1. All these reactions were monitored by 1H-NMR spectroscopy and were found to obey the first-order rate law. From the rate constants at various temperatures, activation parameters were calculated for each reaction. Existence of isokinetic relationship among these three reactions suggests the presence of a common reaction intermediate. Observation of the variable temperature 1H-NMR spectra of [Pd(acac)(γ-acac)py] in pyridine suggests that the activated intermediate may be a species having an oxygen-bonded unidentate acac ligand (“dangling” enolate ligand).