Reusable N-Heterocyclic Carbene Complex Catalysts and Beyond: A Perspective on Recycling Strategies

Abstract

With the continuous development of N-heterocyclic carbene (NHC) chemistry during the past decade, NHC metal complexes have gained wide applications in the research field of organometallic catalysis. The recycling and reuse of NHC metal complexes, which have undergone continuous expansion and diversification, can enhance their catalytic performance, extend their range of application, and afford new routes to green chemistry. Taking NHC metal complex catalysts as the main topic, this review intends to present a comprehensive study of recycling strategies of organometallic catalysts. By an elaborative summarization and classification of recycling strategies, a clear picture of all available of recycling strategies for organometallic catalysts is presented and the advantages and disadvantages of various recycling strategies for specific reactions are discussed in detail. This review is written with the hope of serving as a modest spur to induce other scientists' further contributions in the fields of catalyst recycling and sustainable catalysis.

Dinitrogen Activation by Tricoordinated Boron Species: A Systematic Design

“…To demonstrate N 2 activation by the individual moieties, we started with the NHCs first. Owing to the development of novel synthetic strategies and versatile applicability, NHCs have gained considerable attention . Based on several studies highlighting reactivity of NHCs, cyclic alkyl amino carbenes (CAACs) proved to be more reactive than that of cyclic diamino carbenes (CDACs), due to the presence of one nitrogen atom and σ‐donating tetravalent carbon that decreases their HOMO‐LUMO gaps with the slightly higher HOMO .…”

Chelating Bis(N‐Heterocyclic Carbene) Palladium‐Catalyzed Reactions

“…In addition to discrete complexes, metal–organic frameworks (MOFs) containing Pd–bis(NHC) functionalities are also summarized. We take MOFs into account owing to their ordered structures and isolation of the functionalities in the frameworks; however, this work does not include Pd–bis(NHC) functionalities on polymers, silica, or other carriers, because such compounds were summarized by Ranganath and co‐workers in 2013, and more recently by Kühn and co‐workers, as well as Li and co‐workers …”

A Mechanochemical‐Assisted Synthesis of Boron, Nitrogen Co‐Doped Porous Carbons as Metal‐Free Catalysts

“…The kinetics of cycloaddition of CO 2 with PO was then studied over the GB-6-900/nBu 4 NBr catalysta t1 20 8C. [30] To examine the stability of the B,N-C catalysts, recycling tests were conducted with the conversion of CO 2 with PO over GB-6-900/n-NBu 4 Br under the conditions of 120 8C, 2MPa of CO 2 for 4h. Catalyst recycling is very important in catalysis.…”