Photolysis of Tp'Rh(CNneopentyl)(PhNCNneopentyl) in the presence of ketones and esters: kinetic and thermodynamic selectivity for activation of different aliphatic C-H bonds.

Abstract

The active fragment [Tp'Rh(CNneopentyl)], generated from the precursor Tp'Rh(CNneopentyl)(PhN[double bond, length as m-dash]CNneopentyl), underwent oxidative addition of substituted ketones and esters resulting in Tp'Rh(CNneopentyl)(R)(H) complexes (Tp' = tris-(3,5-dimethylpyrazolyl)borate). These C-H activated complexes underwent reductive elimination at varying temperatures (24-70 °C) in C6D6 or C6D12. Using previously established kinetic techniques, the relative Rh-C bond strengths were calculated. Analysis of the relative Rh-C bond strengths vs. C-H bond strengths shows a linear correlation with slope RM-C/C-H = 1.22 (12). In general, α-substituents increase the relative Rh-C bond strengths compared to the C-H bond that is broken.