Mono and dinuclear rhodium, iridium and ruthenium complexes containing chelating 2,2'-bipyrimidine ligands: Synthesis, molecular structure, electrochemistry and catalytic properties

The mononuclear cations [(?5-C5Me5)RhCl(bpym)]+ (1), [(?5-C5Me5)IrCl(bpym)]+ (2), [(?6-p-PriC6H4Me)RuCl(bpym)]+ (3) and [(?6-C6Me6)RuCl(bpym)]+ (4) as well as the dinuclear dications [{(?5-C5Me5)RhCl}2(bpym)]2+ (5), [{(?5-C5Me5)IrCl}2(bpym)]2+ (6), [{(?6-p-PriC6H4Me)RuCl}2(bpym)]2+ (7) and [{(?6-C6Me6)RuCl}2(bpym)]2+ (8) have been synthesized from 2,2'-bipyrimidine (bpym) and the corresponding chloro complexes [(?5-C5Me5)RhCl2]2, [(?5-C5Me5)IrCl2]2, [(?6-PriC6H4Me)RuCl2]2 and [(?6-C6Me6)RuCl2]2, resp. The x-ray crystal structure analyses of [3][PF6], [5][PF6]2, [6][CF3SO3]2 and [7][PF6]2 reveal a typical piano-stool geometry around the metal centers; in the dinuclear complexes the chloro ligands attached to the two metal centers are , with respect to each other, cis oriented for 5 and 6 but trans for 7. The electrochem. behavior of 1-8 has been studied by voltammetric methods. In addn., the catalytic potential of 1-8 for transfer hydrogenation reactions in aq. soln. has been evaluated: All complexes catalyze the reaction of acetophenone with formic acid to give phenylethanol and carbon dioxide. For both the mononuclear and dinuclear series the best results were obtained (50°, pH 4) with rhodium complexes, giving turnover frequencies of 10.5 h-1 for 1 and 19 h-1 for 5. [on SciFinder(R)]