Theoretical Investigations on the Agostic Interactions of the Molybdenum and Manganese Complexes

The essential participation of agostic interactions in C-H bond activation, cyclometallation and other catalytic processes has been widely observed. To quantitatively evaluate the Mo-H-C agostic interaction in the Mo beta/gamma- agostomers [CpMo(CO)(2)(PiPr(3))](+) (Mo, 1 and Mo, 2) and the Mn-H-C agostic interaction in the Mn alpha/epsilon-agostomers [(C6H9]Mo(CO)(3)] (Mn, 1 and Mn, 2), the comprehensive density functional theory (DFT) theoretical investigations were performed. Results indicated that the Mo beta-agostomer 1 is only favorable by 0.5 kcal mol(-1) than Mo gamma-agostomer 2, and the Gibbs barrier for their interconversion was 9.1 kcal mol(-1). A slightly higher Gibbs barrier of 12.7 kcal mol(-1) for the isomerization between the Mn alpha/epsilon-agostomers was also obtained. The relatively strong agostic interactions in Mo beta-agostomer 1 and Mn alpha-agostomer 1 were further verified by the AIM (Atoms-In-Molecules) analyses and the NAdOs (natural adaptive orbitals) analyses. The findings on the agostic interaction presented in this study are believed to benefit the understandings of the agostic interaction involved catalytic processes and to promote the development of new organometallic complexes.