Electrochemical interactions in binuclear molybdenum and tungsten nitrosyl complexes incorporating saturated n-alkanediolate bridging ligands. Crystal structures of [Mo(NO)(Tp Me2)I{O(CH 2) 2OCOCH 3}] and [W(NO)(Tp Me2)I 2] · 0.5I 2 · 0.5C 6H 5CH 3

Abstract

A series of bimetallic ([{M(NO)(Tp Me2)X} 2(Q)] [Tp Me2 = tris(3,5-dimethylpyrazolyl)borate; M = Mo, X = Cl, Q = O(CH 2) n O, n = 3, 5, 6, or OCH 2(CF 2) 3CH 2O; M = Mo, X = I, n = 3 or 4; M = W, X = Cl, n = 3–6, or OCH 2(CF 2) 3CH 2O; M = W, X = Br, n = 2]), and a number of monometallic complexes (M(NO)(Tp Me2)X(QH)] [M = Mo, X = Cl, Q = O(CH 2) n O, n = 3, or OCH 2(CF 2) 3CH 2O; M = W, X = Br, n = 2]) were prepared. The heterobimetallic complex [{Mo(NO)(Tp Me2)Br}O(CH 2) 2O{W(NO)(Tp Me2)Br}] was also obtained. All compounds were characterised by elemental and mass analyses, 1H NMR and IR spectroscopy. Electrochemical studies (CV and DPV) of the bimetallic species reveal that the metal–metal interactions decrease by ca. 100 mV per CH 2 group with increased length for C 2 to C 4 bridges and become undetectable for complexes with bridges longer than C 4. The substitution of fluorine into the C 5 bridge causes the effect to become measurable due to easier polarisation of the σ-bond framework. The crystal structures of [Mo(NO)(Tp Me2)I{O(CH 2) 2OCOCH 3}] and [W(NO)(Tp Me2)I 2] · 0.5I 2 · 0.5C 6H 5CH 3 were determined.