Exploration of Abnormal N-Heterocyclic Carbene Nickel and Copper Complexes (aNiCu)

点击翻译按钮获取中文摘要

Classical N-heterocylic carbenes (NHCs), 1,3-imidazol-2-ylidenes, are very versatile σ-donor ligands that have led to remarkable advances in organometallic chemistry and catalysis. The widespread success of NHCs is mainly due to their stronger σ-donor ability compared to traditional phosphine ligands. Experimental and theoretical data suggest that abnormal NHCs (aNHCs) (1,3-imidazol-4-ylidenes or 1,3-imidazol-5-ylidenes) are even stronger σ-donors than classical NHCs, perhaps the strongest carbon-donor neutral ligands known till date. Despite their enormous potential in catalysis and beyond, stable aNHC-complexes (particularly with late 3d-metals) are very scarce and most of the reported compounds are serendipitous products. Therefore, the development of rational synthetic methods for aNHC-complexes and their exploration is important and highly desired. This project aims at the synthesis of aNHC-Cu and aNHC-Ni complexes and the exploration of their structure, reactivity, and potential catalytic applications. The proposed synthetic methodologies rely on the use of C2-arylated imidazolium salts, which are readily accessible by the catalytic C2-arylation of NHCs. These salts are promising precursors for the synthesis of aNHCs and functionalized aNHCs. Three sets of ligands namely aNHCs, functionalized aNHCs, and ditopic cabanionic aNHCs (dc-aNHCs) will be investigated. Syntheses of a series of Cu- and Ni-complexes, including heterobimetallic derivatives, are strategic. Reactivity studies of the proposed compounds with small molecules such as CO2, P4, and organic substrates aim to accomplish a fundamental understanding of their “structure-reactivity relationship”, which will be used to uncover their potential applications in catalytic synthesis.