Theoretical investigation of C-H activation in Mg+-CH3X (X=H, NH2 and CHO)

We report a systematic investigation of C-H activation in Mg+-CH3X (X=H, NH2, and CHO) by means of DFT, MP2(Full), and CCSD(T, Full) methods. Geometries for the reactants, intermediates, products, and transition states involved in C-H activation of these reaction systems were fully optimized. Two types of intermediates, H-migrated species and charge-transfer species, were located along the reaction pathways. In contrast with the fact that only one H-migrated species was located for Mg+-NH2CH3 and Mg+-CH4, two analogous minima (HMg+-OCCH3 and HMg+-OCHCH2) were optimized for Mg+-OCHCH3.While no CT species was optimized for Mg+-CH4, we located one analogous minimum for Mg+-NH2CH3 and Mg+-OCHCH3, respectively. The C-H activation processes were carefully traced with the help of IRC calculations. A three-step process was found for C-H activation in Mg+-NH2CH3, whereas C-H activation in Mg+-CH4 and Mg+-OCHCH3 was calculated to be composed of two elementary steps, i.e. hydrogen-migration and nonreactive dissociation. It has been found that the calculated results agree well with previous experimental observations and allow a consistent view on the mechanistic details of this important reaction sequence.