Kinetic and Thermodynamic Investigations of CO2 Insertion Reactions into Ru–Me and Ru–H Bonds – An Experimental and Computational Study

摘要: The rates of CO2 insertion into trans-Ru(dmpe)2(Me)H [1, dmpe = 1,2-bis(dimethylphosphino)ethane] and trans-Ru(dmpe)2(Me)2 (2) derivatives were monitored by in situ infrared 1H NMR spectroscopy. reactions are first order both metal complex concentrations, the Ru–H bond 1 occurs instantaneously at 0 °C. reverse process, decarboxylation, was observed to occur readily ambient temperature as revealed 13CO2 exchange with subsequent Ru–Me higher temperatures. No further resulting acetate observed. activation barrier for 2 determined have ΔH‡ ΔS‡ values 12.7 ± 0.6 kcal mol–1 –31.9 ± 2.0 e.u., respectively, which indicative a highly ordered transition state. rate second two orders magnitude slower resulted formation trans-Ru(dmpe)2(O2CMe)2. In general, or bonds trans-Ru(dmpe)2(X)R (R H Me) disvavored presence poorly electron-donating X ligands. For example, trans-Ru(dmpe)2(Cl)H not even under forcing conditions. Computational results excellent agreement these observations predict significant enhancement activity resultant stability if is replaced tetramethylethylenediamine (tmeda).