Synthesis and characterization of monochelated carboxylatopalladium(II) complexes with nitrogen-donor chelating ligands. Crystal structures of diacetato(1,10-phenanthroline)- and diacetato(2,9-dimethyl-1,10-phenanthroline)-palladium(II)

Two series of monochelated carboxylatopalladium(II) complexes of general formula [Pd(L-L)(MeCO2)2] and [Pd(L-L)(CF3CO2)2] [L-L = 1,10-phenanthroline (phen), 2,2′-bipyridine and their substituted derivatives] have been prepared and characterized. The chemical behaviour of the complexes in solution has been studied in different solvents mainly by means of 1H NMR experiments. These showed that, unlike the acetato complexes, the trifluoroacetato derivatives undergo partial dissociation of the anionic ligand in Me2SO solution at room temperature. A similar behaviour was also observed for the acetato complexes in CD3OD. The signals of the H2,9 protons in the phenanthroline series, and those of H6,6 in the bipyridine one, are excellent probes for the evaluation of the environment of the palladium atom. The crystal structures of [Pd(phen)(MeCO2)2], [Pd(2,9-dmphen)(MeCO2)2]·0.40CH2Cl 2 and [Pd(2,9-dmphen)(MeCO2)2]·0.25CHCl3] (2,9-dmphen = 2,9-dimethyl-1,10-phenanthroline) have been determined. The co-ordination geometry around palladium is square planar in all the structures, but significant deviations from the idealized geometry occur in the last two in order to relieve the interligand contacts. These monochelated carboxylatopalladium(II) complexes are active catalysts in carbon monoxide-olefin copolymerization. Some preliminary results on their catalytic activity are also reported. © Copyright 1994 by the Royal Society of Chemistry.