Unusual Tautomers in Dinuclear Metal Chemistry and Their Role in Oxidative-Addition Reactions of Chlorocarbons

The complex [{Ir(μ-Pz)(CNBut)2}2(Cl)(CH2Ph)] (2), obtained by reaction of [{Ir(μ-Pz)(CNBut)2}2] (1) with PhCH2Cl, presents a very unusual tautomeric equilibrium between the metal−metal-bonded and the mixed-valence complexes [(CNBut)2(Cl)Ir(μ-Pz)2Ir(CH2Ph)(CNBut)2] and [(CNBut)2Ir(μ-Pz)2Ir(Cl)(CH2Ph)(CNBut)2], respectively. This equilibrium allows the unprecedented oxidative-addition reaction of chloroalkanes such as PhCH2Cl and MeCO2CH2Cl to the diiridium(II) complex 2, resulting in the diiridium(III) complex [{Ir(μ-Pz)(CH2Ph)(CNBut)2}2(μ-Cl)]Cl and the mixed-dialkyl complex [(CNBut)2(MeCO2CH2)Ir(μ-Pz)2(μ-Cl)Ir(CH2Ph)(CNBut)2]Cl, respectively.