Multipurpose nitrogen donor ligands for homogeneous transition metal catalysis: from carbonylation to hydrogen generation

The synthesis of novel <i>N,N</i>'-donor ligands as 6/6' substituted bipyridines and the preparation of their Iridium and Palladium complexes for catalytic applications are described. cationic Ir(III) complexes have been applied as photosensitizers in the efficient photoassisted catalyzed by Fe(0) production of hydrogen from water. After screening of different substituents, containing 6-<i>i</i>Pr-2,2'-bipyridine, has been identified as the best photosensitizer. Some of the novel bipyridine ligands have been used in the synthesis of palladium complexes of general formula [Pd(CH3)(CH3CN)(<i>N-N</i>')][PF6] and [Pd(CH3)(<i>N-N</i>')2][PF6]. 6/6' substitution in the bipyridine ligand has led to an improvement of the efficiency of the process. The influence of other reaction parameters has been investigated as well. The use of labelled carbon monoxide 13CO has allowed to spot some reaction intermediate and thus shed some light on the steps where the catalytic cycle is rooted in.