Xuenian Chen
Henan Normal University, China
Title: Agostic interaction influencing catalyst procedure and C-H chemical shift
Biography
Biography: Xuenian Chen
Abstract
Agostic interaction is a weak interaction between an inert C-H and M, which often used to activate C‒H bonds resulting in new reactions. In this topic, we report examples of designed catalysts based on the agostic interaction. Novel copper(I) complexes [BBN(pzx)2]Cu(PPh3)n (BBN=9-borabicyclo[3.3.1]nonane; pzx=3-substituted pyrazole; x=H, n=2; x=Me, n=1) and {[BBN(pziPr)2]Cu}2 have been synthesized and structurally characterized. Single crystal studies of these compounds showed weak intra-molecular C‒H∙∙∙Cu interactions which can be assigned as agostic interactions. Catalytic studies of these complexes toward carbenoid insertion into N‒H bonds indicate these weak interactions act as a “switch” which will be turned “on” if interacting with the substrate and “off” if eliminating the substrate and regenerating the weak interaction. The process of the “switch” turning “on” or “off”, related to the catalytic effect, is found to be influenced by both steric effects and the solvent: a less sterically hindered catalyst in non-coordinating benzene results in high yield, while a more sterically hindered catalyst in coordinating THF results in relatively low yield. We also found that the agostic interaction in nickel containing complex could cause great C-H chemical shift.