Tetraammineruthenium(II) and -ruthenium(III) Complexes of o-Benzoquinone Diimine and Their Redox Series

• Published in: Inorganic chemistry 1997-10, Vol.36 (21), p.4762-4771
• Main Authors: Metcalfe, Robert A, Lever, A. B. P
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic970236c

The complexes [Ru(NH3)4(4,5-R2-bqdi)] n + where bqdi is o-benzoquinone diimine, R = H, Cl, or OMe, and n = 2 or 3 have been characterized by elemental analysis, optical spectroscopy, electrochemistry, spectroelectrochemistry, and electron paramagnetic and nuclear magnetic resonance spectroscopies. ZINDO/S calculations provide a very detailed picture of the degree of mixing existing between metal and ligand orbitals. Both π back-donation and ligand π−d mixing are important such that these compounds are considered to be extensively delocalized. In the RuIII systems compared with the RuII systems, ligand π−d mixing is somewhat more important and π back-donation somewhat less important. Assignments of the electronic spectra are presented in detail in terms of the degree of mixing in the various orbitals. Surprisingly, on the basis of the ZINDO analysis, the lowest energy, strong, visible-region band in the electronic spectra of the RuIII species is shown to be predominantly MLCT and not LMCT as might have been assumed.