SYNTHESIS AND CHARACTERIZATION OF MONOCHELATED CARBOXYLATOPALLADIUM(II) COMPLEXES WITH NITROGEN-DONOR CHELATING LIGANDS - CRYSTAL-STRUCTURES OF DIACETATO(1,10-PHENANTHROLINE) AND TO(2,9-DIMETHYL-1,10-PHENANTHROLINE)-PALLADIUM(II)

Two series of monochelated carboxylatopalladium(II) complexes of gener al formula [Pd(L-L)(MeCO2)2] and [Pd(L-L)(CF3CO2)2] [L-L = 1,10-phenan throline (phen), 2,2'-bipyridine and their substituted derivatives) ha ve been prepared and characterized. The chemical behaviour of the comp lexes in solution has been studied in different solvents mainly by mea ns of H-1 NMR experiments. These showed that, unlike the acetato compl exes, the trifluoroacetato derivatives undergo partial dissociation of the anionic ligand in Me2SO solution at room temperature. A similar b ehaviour was also observed for the acetato complexes in CD3OD. The sig nals of the H-2, H-9 protons in the phenanthroline series, and those o f H-6, H-6 in the bipyridine one, are excellent probes for the evaluat ion of the environment of the palladium atom. The crystal structures o f [Pd(phen)(MeCO2)2], [Pd(2,9-dmphen)(MeCO2)2].0.40CH2Cl2 and [Pd(2,9- dmphen)(MeCO2)2].0.25CHCl3 (2,9-dmphen=2,9-dimethyl-1,10-phenanthrolin e) have been determined. The co-ordination geometry around palladium i s 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) comp lexes are active catalysts in carbon monoxide-olefin copolymerization. Some preliminary results on their catalytic activity are also reporte d.