Synthesis, structure and spectral, and electrochemical properties of new mononuclear ruthenium(III) complexes of tris[(benzimidazol-2-yl)methyl]amine: role of steric hindrance in tuning the catalytic oxidation activity

Murali, Mariappan ; Mayilmurugan, Ramasamy ; Palaniandavar, Mallayan (2009) Synthesis, structure and spectral, and electrochemical properties of new mononuclear ruthenium(III) complexes of tris[(benzimidazol-2-yl)methyl]amine: role of steric hindrance in tuning the catalytic oxidation activity European Journal of Inorganic Chemistry, 2009 (22). pp. 3238-3249. ISSN 1434-1948

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Official URL: http://onlinelibrary.wiley.com/doi/10.1002/ejic.20...

Related URL: http://dx.doi.org/10.1002/ejic.200900119

Abstract

The new mononuclear RuIII complexes [Ru(ntb)Cl2]Cl (1), [Ru(ntb)Cl2]ClO4 (1a), and [Ru(mntb)Cl2]Cl (2) (ntb = tris(benzimidazol-2-ylmethyl)amine, mntb = tris(N-methylbenzimidazol-2-ylmethyl)amine) have been synthesized and characterized. The X-ray crystal structure of 1 reveals that the coordination geometry around the RuIII center is distorted octahedral in which four sites are occupied by the tetradentate ligand ntb and the remaining cis positions by two chloride ions. The stronger Ru-Nbzim bonds elongate the Ru-Cl bonds thereby labilizing the coordinated chloride ions. In the electronic absorption spectra the RuIII complexes show two bands corresponding to π(bzim) → t2g(Ru) and pπ(Cl-) → t2g(Ru) ligand-to-metal charge transfer (LMCT) transitions along with intraligand transitions in the UV region. Complex 1 shows rhombic EPR spectral features (g1, 2.238; g2, 2.071; g3, 1.790). The RuIII complexes display both RuIII → RuII reduction and RuIII → RuIV oxidation processes. Complexes 1 and 2 catalyze the allylic oxidation of cyclohexene, selective and higher epoxidation of cyclooctene, and hydroxylation of alkanes in the presence of the peroxide TBHP and the peracid m-CPBA as cooxidants illustrating that the electronic and steric effects of tripodal 4N ligands can be tuned to catalyze the effective oxidative transformation of organic compounds. ESI-MS studies reveal the formation of ruthenium peroxido species in these catalytic reactions.

Item Type:Article
Source:Copyright of this article belongs to John Wiley and Sons, Inc.
Keywords:Ruthenium(III) Complexes; Electronic Structure; Redox Chemistry; Oxidation; Alkanes; Epoxidation; Alkenes; Ligand Effects
ID Code:30946
Deposited On:27 Dec 2010 06:57
Last Modified:05 Mar 2011 04:49

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