Hydridoiridium(III) sulfoxide complexes and their reactivity toward dioxygen

Abstract

Synthetic routes to hydridoiridium(III) dimethylsulfoxide complexes via oxidative addition of HCl or H 2 to precursor insitu iridium(I) species are described. The complexes, trans, mer-IrHCl 2 (DMSO) 3 (1a) and cis, mer-IrH 2 Cl(DMSO) 3 (2), have been characterized by 1 H nmr and ir, and contain only S-bonded sulphoxide, DMSO. Comparison is made with data for other isomers reported in the literature, and some discrepancies are discussed. The decomposition of 1a and 2 in chloroform leads to isomers of IrCl 3 (DMSO) 3 , while (2) with HCl generates cis,cis IrHCl 2 (DMSO) 2 (DMSO) with the O-bonded sulfoxide trans to hydride. The reaction of 1a in dichloromethane with dioxygen occurs with a 1:1 stoichiometry and generates two complexes tentatively formulated as Ir(OH)Cl 2 (DMSO) 2 H 2 O (3) and IrCl 2 (O 2 )(DMSO) 2 DMSO (4); a hydroperoxide intermediate (Ir—OOH) initially formed from 1a is considered to react with further 1a in the rate-determining step. Oxidation of coordinated DMSO to the sulphone is not observed, implying that such a catalyzed O 2 -oxidation reported earlier in aqueous 2-propanol proceeds via reaction of IrOOH with free DMSO, or else via free hydrogen peroxide.