Abstract
A review. The metal-metal interaction in ligand-bridged diruthenium(II,III) complex intermediates is commonly characterized by using the redox p.d., usually converted to the comproportionation const. Kc, and by analyzing intervalence charge transfer (IVCT) absorption features and deriving electronic coupling parameters. Although these two kinds of information may yield very different ests. of the extent of metal-metal interaction in any given system, the abs. values have often been used interchangeably to quantify the strength of electronic coupling. Using examples from the literature with substantially different coordination arrangements in terms of denticity and donor/acceptor character of the p conjugated bridging ligand close correlations between electrochem. and spectroscopically detd. coupling are only valid within structurally related classes of compds. with qual. similar interaction at the metal-ligand interface. Most strikingly, situations with high Kc values but weak, low energy IVCT absorptions were identified for complexes with bis- and tris-bidentate acceptor bridges whereas intermediates with small comproportionation consts. but intense, narrow IVCT bands are typical with bridging bis-tridentate acceptors. [on SciFinder(R)]
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