Bis(iminoxolene)iridium Anion and Alkyls: How Does Ligand Redox Noninnocence Interface with Oxidative Addition?

The bis(iminoxolene) complex (Diso)2IrCl (Diso = N-(2,6-diisopropylphenyl)-4,6-di-tert-butyl-2-imino-o-benzoquinone) is reduced by two equivalents of sodium naphthalenide to give square planar, diamagnetic Na[(Diso)2Ir]. The anionic iridium center acts as a nucleophile to primary and secondary alkyl and allyl halides to give square pyramidal iridium alkyls. Benzoyl chloride reacts to give an iridium benzoyl complex. Organoiridium complexes are also formed by reaction of (Diso)2IrCl with Grignard reagents, and treatment with acetone in the presence of base gives the κ1 carbon-bonded enolate complex (Diso)2IrCH2COCH3. The solid-state structures of the primary alkyls show significant inclinations of the iridium–carbon bond away from the 2-fold axis of the square pyramid, apparently for steric reasons. The relative reactivity of substrates and exclusive formation of (Diso)2Ir(5-hexenyl) from 6-bromo-1-hexene indicate that primary alkyl halides react by an SN2 mechanism. Structural data suggest that the oxidative addition is about 70% metal-centered, consistent with nucleophilic behavior that is analogous to that of other square planar group 9 anions.