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

The complex [{Ir(μ-Pz)(CNBu<sup>t</sup>)<sub>2</sub>}<sub>2</sub>(Cl)(CH<sub>2</sub>Ph)] (<b>2</b>), obtained by reaction of [{Ir(μ-Pz)(CNBu<sup>t</sup>)<sub>2</sub>}<sub>2</sub>] (<b>1</b>) with PhCH<sub>2</sub>Cl, presents a very unusual tautomeric equilibrium between the metal−metal-bonded and the mixed-valence complexes [(CNBu<sup>t</sup>)<sub>2</sub>(Cl)Ir(μ-Pz)<sub>2</sub>Ir(CH<sub>2</sub>Ph)(CNBu<sup>t</sup>)<sub>2</sub>] and [(CNBu<sup>t</sup>)<sub>2</sub>Ir(μ-Pz)<sub>2</sub>Ir(Cl)(CH<sub>2</sub>Ph)(CNBu<sup>t</sup>)<sub>2</sub>], respectively. This equilibrium allows the unprecedented oxidative-addition reaction of chloroalkanes such as PhCH<sub>2</sub>Cl and MeCO<sub>2</sub>CH<sub>2</sub>Cl to the diiridium(II) complex <b>2</b>, resulting in the diiridium(III) complex [{Ir(μ-Pz)(CH<sub>2</sub>Ph)(CNBu<sup>t</sup>)<sub>2</sub>}<sub>2</sub>(μ-Cl)]Cl and the mixed-dialkyl complex [(CNBu<sup>t</sup>)<sub>2</sub>(MeCO<sub>2</sub>CH<sub>2</sub>)Ir(μ-Pz)<sub>2</sub>(μ-Cl)Ir(CH<sub>2</sub>Ph)(CNBu<sup>t</sup>)<sub>2</sub>]Cl, respectively.