Pub No:
Synthesis and Redox Chemistry of Octaethylporphyrin Complexes of Ruthenium(II) and Ruthenium(III)
Barley, M., Becker, J.Y., Domazetis, G., David Dolphin, and James, B.R.
Can. J. Chem.,
61, 2389-2396
The syntheses and characterization of new octaethylporphyrin complexes Ru(OEP)(PBu3)2, Ru(OEP)(CO)L (L = PPh3, PBu3), [Ru(OEP)(PBu3)2]Br, and Ru(OEP)(PBu3)Br (OEP is the dianion of octaethylporphyrin) are described. Ru(OEP)(CO)EtOH (I) which reversibly loses the ethanol ligand in CH2Cl2 solution,undergoes a one-equivalent oxidation at the porphyrin ligand to generate the cation-radical [Ru(OEP) (CO)]+., a purple species of 2A2u ground state, produced electrochemically in perchlorate media, can coordinate bromide to generate a green 2A1u ground state species that also results from oxidation of I using bromine. Coordination of pyridine to [Ru(OEP) CO]+ yields the Ru(OEP) (CO)py species that can also be formed by electrochemical oxidation of Ru(OEP)(CO)py. Addition of tertiary phosphines (PR3) to the cation-radical carbonyl species can lead to [Ru(OEP)(PR3)2]+, via an internal electron transfer process from Ru(II) to the OEP+ that appears to be triggered by loss of the CO ligand. A reversible one-electron electrochemical oxidation of Ru(OEP)(PBu3)2 at 0.03 V (vs. Ag/AgCl) in CH2Cl2 also gives the ruthenium(III) biphosphine cation, while a further one-electron oxidation at 1.2 V generates [Ru(OEP) (PBu3)22+, a ruthenium(III) π-cation radical characterized by ESR. The [Ru(OEP)(PBu3)2]Br complex decomposes in the solid state to a mixture of Ru(OEP)(PBu3)Br, formed together with phosphine via an intramolecular ligand exchange, and Ru(OEP)(PBu3)2, formed by reduction of the initial ionic ruthenium(III) cation with the phosphine that appears as [PBu3Br]Br.

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