New Perspective on the Formation and Reactivity of Metal−Metal-Bonded Dinuclear Rhodium and Iridium Complexes

Abstract

Reactions of the binuclear complexes [{M(μ-Pz)(CNBut)2}2] (M = Rh (1), Ir (2); Pz = pyrazolate) with diiodine give the metal−metal-bonded complexes [{M(μ-Pz)(I)(CNBut)2}2] (M = Rh (3), Ir (4)). A further reaction with diiodine afford the complexes [{M(μ-Pz)(I)(CNBut)2}2(μ-I)]I, which react cleanly with CF3SO3Me replacing the ionic iodide by the triflate group. The M(I) complexes 1 and 2 are easily oxidized by mild oxidants such as [Cp2Fe]+ to give the metal−metal-bonded dications [{M(μ-Pz)(CNBut)2(MeCN)}2]2+, which add halide ions yielding the neutral complexes [{M(μ-Pz)(X)(CNBut)2}2] (M = Rh, X = Cl (7); M = Rh, Ir, X = I). These reactions indicate that the metal−metal bond formation has an electron-transfer character. Evidence of the nucleophilic attack by the metal−metal bond in complexes 3 and 4 of small molecules such as diiodine is provided by the reaction of [I(Py)2]BF4 with 7, which adds the electrophilic iodine(I) to give the bridging iodide complex [{Rh(μ-Pz)(Cl)(CNBut)2}2(μ-I)]+. In addition, a...