The blue dimmer[1],[2],[3],[4] and OEC complexes initiated a long lasting interest in high-valent metal complexes as possible intermediates in the water oxidation reaction. Recently, we proposed mechanistic significance of non-covalent interaction between axial ligands in monomeric Ru(bda) complexes in the course of the O-O bond formation step[5]. Here we report recent results for a series of complexes using DMSO and Imidazole as axial ligands[6]. Our results show that the complexes with DMSO as axial ligand may in fact have a better support of different oxidation states via O-M or S-M bonds in comparison to complexes bearing equivalent axial ligands like Imidazole. We have found a reason for the experimentally observed fact that DMSO facilitates the catalytic activity presumably by promoting both O-O bond formation and O2 liberation steps thus explaining the experimentally observed high turnover frequency (TOF ~ 180 s-1) of the complexes bearing DMSO/Imidazole as the axial ligand combination in comparison to the Ru complexes having just two equivalent Imidazole axial ligands (TOF ~ 4.6 s-1). In addition, DFT calculated redox potentials of proton coupled steps for both RuIII/RuIV, RuIV/RuV are presented and their place in mechanism is highlighted.1. Gersten, S. W.; Samuels, G. J.; Meyer, T. J. J. Am. Chem. Soc. 1982 ,104,4029.[2]. Concepcion, J.; Jurss, W.; Brennaman, K.; Horetz, G.; Patrcinio, A.; Murakami, N.; Templeton, J.; Meyer, T. Acc. Chem. Res. 2009 ,42,1954.[3]. Roman, S.; Vigara, L.; Llobet, A.; Acc. Chem. Res. 2009 , 42, 1944.[4]. Dau, H.; Limberg, C.; Reier, T.; Risch, M.; Roggan, s.; Strasser, P. ChemCatChem. 2010 ,2,724.[5]. Duan, L.; Bozoglian, F.; Mandal, S.; Stewart, B.; Privalov, T.; Llobet, A.; Sun, L. Nature Chem. 2012 , 4, P418.[6]. Wang, L.; Duan, L.; Stewart, B.; Pu, M.; Liu, J.; Privalov, T.; Sun, L. J. Am. Chem. Soc. DOI: 10.1021/ja309805m.

Toward controlling water oxidation catalysis: A model of the tunable activity of ruthenium complexes with axial imidazole/DMSO ligands

245th National Meeting (2013)

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