Source: School of Materials Science and Engineering
Written by: School of Materials Science and Engineering
Edited by: Wang Dongmei

Shortage of fossil fuels and their resulted pollutants are increasingly challenging due to the increasing demand of energy in modern society. Renewable energy without environmental detriment is of profound importance for the expanding human needs. Hydrogen energy, as a cleanly renewable source, has great potential to meet global energy and environmental requirements. Therefore, many researchers devote themselves to seek efficient catalysts for renewable utilization of hydrogen energy via chemical bonds in mid conditions. At present, the popular method is to biomimic the function of active center in hydrogenase to activate H₂ by Lewis base – transition metal (LB-TM) catalysts, in which the Lewis base site abstracts proton and the transition metal center accepts hydride during heterolytic H₂ cleavage.

Recently, Zhuofeng Ke’s group at Sun Yat-sen University reported general hydrogen activation modes for novel type of Lewis acid – transition metal (LA-TM) catalysts. Differ from traditional LB-TM catalysts, the LA-TM catalyst is conventionally new bearing an electron deficiency Lewis acid site for H₂ activation, in which the Lewis acid site functions as electrophile to accept hydride during H2 cleavage. Using (^PhDPB^Ph)-Ni as a representative LA-TM catalyst, they presented four general hydrogen activation modes for the LA-TM catalyzed H₂ activation vi systematically DFT studies, including: (1) the cis homolytic mode through a cis dihydride intermediate, in which Lewis acid stabilizes the dz² electron of transition metal; (2) the trans homolytic mode to a trans dihydride complex, in which the LA datively interacts with transition metal during cleavage; (3) the synergetic heterolytic mode, in which H₂ cleaves cooperatively assisted by both the Lewis acid and transition metal; (4) the dissociative heterolytic mode, in which the Lewis acid and transition metal assist H₂ cleavage in dissociative manner. These modes should provide a general mechanistic framework for the development and rational design of LA-TM catalysts in the future. 

This paper is published in ACS Catalysis with PhD student Yinwu Li as the first author. This work was supported by the NSFC Foundation (grants 21203256 and 21473261) and the Guangdong Natural Science Funds for Distinguished Young Scholar (no. 2015A030306027).

Li, Yinwu; Hou, Cheng; Jiang, Jingxing; Zhang Zhihan; Zhao, Cunyuan, Page, Alister J.; Ke, Zhuofeng*. General H2 Activation Modes for Lewis Acid–Transition Metal Bifunctional Catalysts. ACS Catal. 2016, 6, 1655–1662
http://pubs.acs.org/doi/abs/10.1021/acscatal.5b02395