School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK.
Dalton Trans. 2011 Oct 28;40(40):10278-88. doi: 10.1039/c1dt10864f. Epub 2011 Jul 26.
Poly-NHC (NHC = N-heterocyclic carbene) ligands emerged almost immediately after the first stable NHCs had been described. Macrocyclic ligands, featuring NHC donor groups and their metal complexes, however, remained rare until recently. This perspective highlights modern developments in the fields of synthesis and coordination chemistry of macrocyclic poly-NHC ligands. These include the synthesis of tetracarbene ligands which were obtained from complexes of β-functionalized isocyanides followed by cyclization of the coordinated iscocyanide ligands to NH,NH-functionalized NHCs and the subsequent metal template controlled bridging alkylation of the NH,NH-NHCs to yield the macrocycle. The template synthesis of ligands featuring a mixed NHC/phosphine donor set like [11]ane-P(2)C(NHC) and [16]ane-P(2)C(NHC)(2) by linkage of NH,NH-NHCs to different phosphines is also presented. Finally, methods for the preparation of cyclic polyazolium salts, their deprotonation and metalation and the different modes of coordination of such macrocyclic poly-NHC ligands are discussed.
多齿 N-杂环卡宾（NHC=N-杂环卡宾）配体几乎与第一批稳定的 NHC 被描述的同时出现。然而，直到最近，具有 NHC 供体基团及其金属配合物的大环配体仍然很少见。本文重点介绍了大环多齿 NHC 配体的合成和配位化学领域的现代发展。这些发展包括四齿卡宾配体的合成，这些配体是由β-功能化异氰化物的配合物获得的，然后通过配位异氰化物配体与 NH，NH-功能化 NHC 的环化，以及随后的 NH，NH-NHC 的金属模板控制桥接烷基化来生成大环。通过将 NH，NH-NHC 连接到不同的膦上，也可以合成具有混合 NHC/膦供体的配体[11]ane-P(2)C(NHC)和[16]ane-P(2)C(NHC)(2)。最后，讨论了环状聚唑盐的制备方法、脱质子和金属化以及此类大环多齿 NHC 配体的不同配位模式。
