Strategy II. Redox non-innocent ligands as electron reservoirs

3 Strategy II. Redox non-innocent ligands as electron reservoirs 

Water oxidation is a thermodynamically unfavorable process which involves the transfer of four electrons. Several catalysts have been developed and simultaneously several mechanisms for these types of chemical transformations have been proposed [13]. Binuclear ruthenium complexes have drawn considerable attention in the context of water oxidation. The anthracene-bridged binuclear Ru bis-hydroxide bis-quinone 

The counterpart of catalytic water oxidation to O, catalytic evolution via water reduction, is of equal importance in the context of water splitting (artificial photosynthesis) [15]. Innature, hydrogenase enzymes show excellent catalytic rates and efficiencies and can catalyze both proton reduction and oxidation. Consequently, several biomi-metic complexes have been developed which show excellent catalytic activity towards electrochemical production from water. 

Significant progress in the application of this concept has also been made in catalytic C—C bond formation reactions. Chirik and co-workers recently reported an interesting case involving [2jc +2jc] cycloaddition of dienes and enynes using the bis-dinitrogen 

Interestingly, the electron reservoir properties of redox active ligands are also found to be useful to impose one-electron transformation on late transition metals. Rhenium complexes are known to be powerful oxo-transfer reagents [27]. However, closed-shell 

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