Redox activity of bimetallic complexes based on tris(3,5-dimethylpyrazolyl)borato molybdenum(II) and tungsten(II) nitrosyls.: Complexes derived from ethane-1,2-diol and the crystal structure of anti-[Mo(NO){HB(3,5-Me2C3HN2)3}-(OCH2CH2O)]2•4CHCl3

The bimetallic complexes [{ M(NO)(Tp(Me2))X}(2)(OCH2,CH2O)] [Tp (Me2) = HB(3,5-Me2C3HN2)(3); M = Mo, X = Cl, Br or I; M = W, X = Cl] have been synthesised and characterised spectroscopically and electrochemically. These species can occur as mixture of two diastereoisomers and one of them could be separated following a thermal treatment of the mixture. A direct synthesis of single diastereoisomers (M = Mo, X = I; M = W, X = Cl) is also described. The bimetallic species exhibit two one-electron reduction processes separated by a modest potential difference, Delta E-1/2, ca. 300 mV (M = Mo, X = Cl, Br) indicating an intermediate metal-metal interaction. In the crystal structure of anti-[ {Mo(NO)(Tp(Me2))(OCH2CH2O)}(2)] center dot 4CHCl(3) two nonequivalent dinuclear molecules (point group C-2h) are found, with crystallographically identical, doubly bridged { Mo(NO)(Tp(Me2)) } distorted octahedral units. (C) 2006 Elsevier Ltd. All rights reserved.