Addition of neutral ligands to the trigonal prismatic iridium tetrahydride ( iprBDI)IrH 4 (BDI = ArNC(Me)CH(Me)CNAr, Ar = 2,6- iPr 2C 6H 3) induces reductive elimination of dihydrogen to afford ( iprBDI)IrH 2(L) (L = phosphine, tetrahydrothiophene, cyclohexene) compounds. A combination of solution NMR data and infrared spectroscopic studies have established that the phosphine dihydride compounds and the cyclohexene adduct are best described as classical iridium(III) dihydride or "stretched dihydrogen" complexes. The corresponding tetrahydrothiophene adduct exhibits spectroscopic features and reactivity patterns consistent with increased iridium(I) dihydrogen character. In complexes containing large cone angle phosphines such as PCy 3 and P iPr 3, ligand dissociation is facile and isotopic exchange in arene substrates is observed. The experimental data support an Ir(III)-Ir(V) oxidative addition-reductive elimination sequence for C-H bond activation, in contrast to more traditional coordinatively saturated precursors, where Ir(I)-Ir(III) couples are preferred.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry