The effects, assessed by electrochemical techniques and single crystal structures, of ortho substitution on benzoate ligands supporting the quadruply-bonded dimolybdenum bond

The syntheses, electrochemistry and structures of Mo2(O2C-o-C6H4Cl)4, 1·4THF, Mo2(O2C-o-C6H4Br)4, 2·2THF, Mo2(O2C-o-C6H4I)4, 3·2THF, and Mo2(O2C-o-C6H4NO2)4 (4), as determined by single-crystal X-ray diffraction, are reported. Molecules 1, 2, and 3 co-crystallized each with two axially coordinated THF molecules; complex 1 contained two more THF molecules within the unit cell. The MoMo distances in 1–4 are 2.1029(10), 2.1014(13), 2.1055(7), and 2.0942(12) Å, respectively. The oxidation potentials for 1–3 were similar at 674, 655, and 647 mV, but that for 4 at an E1/2(ox) of 792 mV was higher.