SILVER(I) N-HETEROCYCLIC CARBENES

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Abstract
This review presents a detailed overview on the synthesis of AgI–NHCs and their role as carbene transferring agents as an easy access to various important transition metal-NHC complexes. The nature of NHC ligands, counter anions and solvents are recognized as key factors in the determination of AgI–NHCs and their derivatives. The lack of Ag–Ccarbene bond coupling in various AgI–NHCs suggests the lability of Ag–Ccarbene bond, which appears to be an appropriate reason in the transfer of carbene. It has been suggested by various authors that carbene transfer from AgI–NHCs is particularly useful when the carbene N-functionality contains base sensitive functional groups or acidic hydrogen. Importantly AgI–NHCs are less air sensitive than the free carbenes and are easy to synthesize. These properties allow them to be handled easily in further operations. Apart from the carbene transferring property, the nature of Ag–Ccarbene bond, the influence of NHC on the Ag…Ag contacts and the molecular aggregation to generate novel structural motifs and supramolecular assemblies have also been emphasized.