Palladium Complexes Containing Large Fused Aromatic N−N Ligands as Efficient Catalysts for the CO/Styrene Copolymerization

Bis(homoleptic) palladium(II) complexes of the extended aromatic ligands eilatin ([Pd(eil) 2 ][BF 4 ] 2 ( 1a )) and dipyridophenazine ([Pd(dppz) 2 ][BF 4 ] 2 ( 2a ), [Pd(dppz) 2 ][PF 6 ] 2 ( 2b )) were synthesized and employed in the copolymerization of carbon monoxide and styrene. The eilatin ligand in the complex [Pd(eil) 2 ][BF 4 ] 2 is bound via its less hindered “head” coordination site. The X-ray structure of 2b was solved and indicated a highly twisted square planar geometry around the palladium center and the presence of π-stacking interactions of two types. All complexes were found to be active catalysts for the synthesis of the syndiotactic CO/styrene polyketone, their activity exceeding that of the parent complex [Pd(phen) 2 ][BF 4 ] 2 .