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Mono and dinuclear rhodium, iridium and ruthenium complexes containing chelating 2,2′-bipyrimidine ligands: Synthesis, molecular structure, electrochemistry and catalytic properties |
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| Authors: | Padavattan Govindaswamy Bruno Therrien Petr Štěpni?ka Ji?í Ludvík |
| Institution: | a Institut de Chimie, Université de Neuchâtel, Case postale 158, CH-2009 Neuchâtel, Switzerland b Charles University, Faculty of Natural Science, Department of Inorganic Chemistry, Hlavova 2030, CZ-12840 Prague 2, Czech Republic c J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejškova 3, CZ-18223 Prague, Czech Republic |
| Abstract: | The mononuclear cations (η5-C5Me5)RhCl(bpym)]+ (1), (η5-C5Me5)IrCl(bpym)]+ (2), (η6-p-PriC6H4Me)RuCl(bpym)]+ (3) and (η6-C6Me6)RuCl(bpym)]+ (4) as well as the dinuclear dications {(η5-C5Me5)RhCl}2(bpym)]2+ (5), {(η5-C5Me5)IrCl}2(bpym)]2+ (6), {(η6-p-PriC6H4Me)RuCl}2(bpym)]2+ (7) and {(η6-C6Me6)RuCl}2(bpym)]2+ (8) have been synthesised from 2,2′-bipyrimidine (bpym) and the corresponding chloro complexes (η5-C5Me5)RhCl2]2, (η5-C5Me5)IrCl2]2, (η6-PriC6H4Me)RuCl2]2 and (η6-C6Me6)RuCl2]2, respectively. 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 centres; in the dinuclear complexes the chloro ligands attached to the two metal centres are found to be, with respect to each other, cis oriented for 5 and 6 but trans for 7. The electrochemical behaviour of 1-8 has been studied by voltammetric methods. In addition, the catalytic potential of 1-8 for transfer hydrogenation reactions in aqueous solution has been evaluated: All complexes catalyse 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 °C, pH 4) with rhodium complexes, giving turnover frequencies of 10.5 h−1 for 1 and 19 h−1 for 5. |
| Keywords: | Arene ligands Dinuclear complexes Transfer hydrogenation N ligands Electrochemistry |
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