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

The complex [{Ir(μ-Pz)(CNBu^t)₂}₂(Cl)(CH₂Ph)] (2), obtained by reaction of [{Ir(μ-Pz)(CNBu^t)₂}₂] (1) with PhCH₂Cl, presents a very unusual tautomeric equilibrium between the metal−metal-bonded and the mixed-valence complexes [(CNBu^t)₂(Cl)Ir(μ-Pz)₂Ir(CH₂Ph)(CNBu^t)₂] and [(CNBu^t)₂Ir(μ-Pz)₂Ir(Cl)(CH₂Ph)(CNBu^t)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)(CNBu^t)₂}₂(μ-Cl)]Cl and the mixed-dialkyl complex [(CNBu^t)₂(MeCO₂CH₂)Ir(μ-Pz)₂(μ-Cl)Ir(CH₂Ph)(CNBu^t)₂]Cl, respectively.