Cyanide-bridged linkage isomers with catecholateruthenium(ii) centres bound to Mn(i) or M(alkyne) units.

Two series of stable cyanide-bridged linkage isomers, namely [(o-O2C6Cl4)(Ph3P)(OC)2Ru(µ-XY)MnL(NO)(η-C5Me5)] (XY = CN or NC, L = CNBut or CNXyl) and [(o-O2C6Cl4)L(OC)2Ru(µ-XY)M(CO)(PhC&z.tbd;CPh)Tp′] {M = Mo or W, L = PPh3 or P(OPh)3, Tp′ = hydrotris(3,5-dimethylpyrazolyl)borate} have been synthesised; pairs of isomers are distinguishable by IR spectroscopy and cyclic voltammetry. The molecular structure of [(o-O2C6Cl4)(Ph3P)(OC)2Ru(µ-NC)Mo(CO)(PhC&z.tbd;CPh)Tp′] has the catecholate-bound ruthenium atom cyanide-bridged to a Mo(CO)(PhC&z.tbd;CPh)Tp′ unit in which the alkyne acts as a four-electron donor; the alignment of the alkyne relative to the Mo–CO vector suggests the fragment (CN)Ru(CO)2(PPh3)(o-O2C6Cl4) acts as a π-acceptor ligand. The complexes [(o-O2C6Cl4)(Ph3P)(OC)2Ru(µ-XY)Mn(NO)L(η-C5Me5)] undergo three sequential one-electron oxidation processes with the first and third assigned to oxidation of the ruthenium-bound o-O2C6Cl4 ligand; the second corresponds to oxidation of Mn(i) to Mn(ii). The complexes [(o-O2C6Cl4)L(OC)2Ru(µ-XY)M(CO)(PhC&z.tbd;CPh)Tp′] are also first oxidised at the catecholate ligand; the second oxidation, and one-electron reduction, are based on the M(CO)(PhC&z.tbd;CPh)Tp′ fragment. Chemical oxidation of [(o-O2C6Cl4)(Ph3P)(OC)2Ru(µ-XY)MnL(NO)(η-C5Me5)] with [Fe(η-C5H4COMe)(η-C5H5)][BF4], or of [(o-O2C6Cl4)L(OC)2Ru(µ-XY)M(CO)(PhC&z.tbd;CPh)Tp′] with AgBF4, gave the paramagnetic monocations [(o-O2C6Cl4)(Ph3P)(OC)2Ru(µ-XY)MnL(NO)(η-C5Me5)]+ and [(o-O2C6Cl4)L(OC)2Ru(µ-XY)M(CO)(PhC&z.tbd;CPh)Tp′]+, the ESR spectra of which are consistent with ruthenium-bound semiquinone ligands. Linkage isomers are distinguishable by the magnitude of the 31P hyperfine coupling constant; complexes with N-bound Ru(o-O2C6Cl4) units also show small hyperfine coupling to the nitrogen atom of the cyanide bridge. [ABSTRACT FROM AUTHOR]