Isolated seven-coordinate Ru(IV) dimer complex with [HOHOH](-) bridging ligand as an intermediate for catalytic water oxidation

Lele Duan; Andreas Fischer; Yunhua Xu; Licheng Sun

doi:10.1021/ja9034686

Isolated seven-coordinate Ru(IV) dimer complex with [HOHOH](-) bridging ligand as an intermediate for catalytic water oxidation

J Am Chem Soc. 2009 Aug 5;131(30):10397-9. doi: 10.1021/ja9034686.

Authors

Lele Duan¹, Andreas Fischer, Yunhua Xu, Licheng Sun

Affiliation

¹ Department of Chemistry, School of Chemical Science and Engineering, Royal Institute of Technology (KTH), 100 44 Stockholm, Sweden.

PMID: 19601625
DOI: 10.1021/ja9034686

Abstract

With the inspiration from an oxygen evolving complex (OEC) in Photosystem II (PSII), a mononuclear Ru(II) complex with a tetradentate ligand containing two carboxylate groups has been synthesized and structurally characterized. This Ru(II) complex showed efficient catalytic properties toward water oxidation by the chemical oxidant cerium(IV) ammonium nitrate. During the process of catalytic water oxidation, Ru(III) and Ru(IV) species have been successfully isolated as intermediates. To our surprise, X-ray crystallography together with HR-MS revealed that the Ru(IV) species is a seven-coordinate Ru(IV) dimer complex containing a [HOHOH](-) bridging ligand. This bridging ligand has a short O...O distance and is hydrogen bonded to two water molecules. The discovery of this very uncommon seven-coordinate Ru(IV) dimer together with a hydrogen bonding network may contribute to a deeper understanding of the mechanism for catalytic water oxidation. It will also provide new possibilities for the design of more efficient catalysts for water oxidation, which is the key step for solar energy conversion into hydrogen by light-driven water splitting, the ultimate challenge in artificial photosynthesis.