Synthesis and reactions of heterodinuclear organopalladium–cobalt complexes acting as copolymerization catalyst for aziridine and carbon monoxide

A series of heterodinuclear acylpalladium–cobalt complexes having a bidentate nitrogen ligand, L2(RCO)Pd–Co(CO)4 (L2 = bpy, R = Me (5), Ph (6); L2 = tmeda, R = Me (7), Ph (8); L2 = phen, R = Me (9), Ph (10)) are prepared by metathetical reactions of PdRIL2 with Na+[Co(CO)4]− followed by treatment with CO. These complexes are characterized by NMR and IR spectroscopies and elemental analyses, and the molecular structures of 6, 8, and 9 are determined by X-ray structure analysis. Geometry at Pd is essentially square planar and the Co atom is considered to have d10 tetrahedral structure, where cobalt(-I) anion coordinates to palladium(II) cation. Heterodinuclear organopalladium–cobalt complexes are shown to catalyze copolymerization of aziridines and CO under mild conditions. Reaction of (dppe)MePd–Co(CO)4 (1) with aziridine gives a cationic (aziridine)palladium(II) complex with [Co(CO)4]− anion, [PdMe(aziridine)(dppe)]+[Co(CO)4]− (13).