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On the Role of the Bridging Dicyanamidobenzene Ligand in a New Binuclear Ruthenium Complex: [{Ru(tpy)(thd)}2(mu-dicyd)][PF6] With Tpy = 2,2':6',2' '-Terpyridine and THD = 2,2,6,6-tetramethyl-3,5-heptanedione

Muriel Fabre, Joël Jaud, Mohamed Hliwa, Jean-Pierre Launay, Jacques Bonvoisin

Inorg Chem. 2006 Nov 13;45(23):9332-45.

PMID: 17083233

Abstract:

The dicyanamidobenzene-bridge diruthenium complex [{Ru(tpy)(thd)}(2)(mu-dicyd)][PF(6)] ([3][PF(6)]) (dicyd = 1,4-dicyanamidobenzene, tpy = 2,2':6',2' '-terpyridine, thd = 2,2,6,6-tetramethyl-3,5-heptanedione) and its mononuclear counterpart [Ru(tpy)(thd)(Ipcyd)] (2) [Ipcyd = 4-iodophenylcyanamide anion (Ipcyd(-))] were synthesized and fully characterized. Cyclic voltammetry of 3 showed the presence of four reversible one-electron redox couples. UV-vis-NIR spectroelectrochemistry and EPR spectroscopy of the electrogenerated paramagnetic intermediates were used to ascertain the oxidation-state distribution. The stable starting dinuclear complex 3(+) is found to be a ligand-centered anion radical as shown by EPR spectroscopy, magnetic susceptibility measurements, and DFT calculations. Oxidation of 3(+) to 3(2+) led to an EPR silent system due to substantial intramolecular antiferromagnetic interaction of the electron spins carried by the low spin ruthenium(III) atom and the bridging anion radical dicyanamido (dicyd(*)(-)), an observation which was supported by UV-vis-NIR, X-ray structure, and DFT calculations. Complex 3(3+) presented an EPR spectra consistent with a total effective spin S = (1)/(2) issued from an antiferromagnetic interaction of electron spins carried by two low spin ruthenium(III) atoms and the bridging anion radical dicyd(*)(-) in accordance with UV-vis-NIR. This study shows that the dicyanamidobenzene bridging ligand has indubitably a noninnocent behavior.

Chemicals Related in the Paper:

Catalog Number Product Name Structure CAS Number Price
AP1118714 2,2,6,6-Tetramethyl-3,5-heptanedione 2,2,6,6-Tetramethyl-3,5-heptanedione 1118-71-4 Price
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