Carbon–hydrogen and carbon–heteroatom bond activation using iridium(I) complexes

Abstract

In this research, the B3LYP density functional and Stevens effective core potentials are used to compare carbon–hydrogen and carbon–heteroatom bond activation by an iridium(I) complex. Of particular importance is to address the kinetic (transition state) and thermodynamic (ground state) selectivity. The complex Ir(PH 3) 2(H) with CH 3–X (X=F, Cl, OH, SH, NH 2, PH 2) as the substrate has been used as a model. Good agreement in geometries is obtained between the target molecules and experimental models. The resultant products of C–H and C–X oxidative addition are Y-shaped minima (i.e., a distorted trigonal bipyramid with one acute and two obtuse angles among the equatorial ligands). Oxidative addition of the C–X bond to the substrate is exothermic for groups 16 and 17, but endothermic for group 15. A significant thermodynamic preference for C–X activation over C–H activation is observed for these Ir(I) complexes. However, analysis of the transition states for oxidative addition suggests that there is a kinetic preference for C–H activation.