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)(TpMe2)X}2(OCH2CH2O)] [TpMe2 = 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, ΔE1/2, ca. 300 mV (M = Mo, X = Cl, Br) indicating an intermediate metal–metal interaction. In the crystal structure of anti-[{Mo(NO)(TpMe2)(OCH2CH2O)}2] · 4CHCl3 two nonequivalent dinuclear molecules (point group C2h) are found, with crystallographically identical, doubly bridged {Mo(NO)(TpMe2)} distorted octahedral units.