In the last decades, N-heterocyclic carbenes (NHCs) have proven themselves as successor to classical ligands such as phosphines, carbonyls, cyclopentadienyls etc.1,2 The strong -donor capability of NHCs and ease of alteration of their electronic as well as steric properties have made them an obvious choice for various metal-based chemistry.3 The key applications of NHC ligands lies in the area of homogeneous catalysis although recently found suitable for the construction of metal assisted three-dimensional assemblies. These assemblies have potential applications in host-guest/medicinal chemistry while the specially designed hetero-bimetallic catalysts can be used for orthogonal tandem catalysis.4,5 Recent studies suggest that (benz)imidazolium-based poly(azolium) salts serve as excellent NHC precursors for the construction of above-mentioned assemblies as well as heterobimetallic catalysts as they can providing the rigid platform required for fixing the two metals effectively.5 Hence, we aimed to synthesize various types of NHC precursors [L1-H3](PF6)3, [L2-H2](Br)2, and [L3-H]Br, (figure 1a) featuring different coordination sites to employ them in the formation of coinage metal assisted self-assembled structures as well as heterobimetallic complexes.

Figure 1. a) Imidazole and benzimidazole based precarbene ligands. b) Selected crystal structures of self-assembled AgI-NHC complex, mono-metallic IrIII and hetero-bimetallic IrIII/PdII metal NHC complexes.

[L1-H3](PF6)3/[L2-H2](BF4)2 were used for the synthesis of unique multinuclear MI-polycacarbene complexes (M = Ag/Cu/Au),6 while several heterobimetallic complexes (IrIII-PdII/AuI) were synthesized from [L2-H2]Br2 (figure 1b). The IrIII/PdII heterobimetallic complex was used for several tandem catalytic transformations such as transfer hydrogenation and Suzuki-Miyaura coupling/hydrodehalogenation reactions. Detailed account of the multinuclear self-assembly and the tandem catalysis will be presented in the seminar.

References. 1) Glorius, F.; Hopkinson, M. N.; Richter, C. Nature 2014, 510, 485; 2) Hahn, F. E.; Jahnke, M. C. Angew. Chem. Int. Ed. 2008, 47, 3122. 3) Huynh, H. V. Chem. Rev. 2018, 118, 9457. 4) Sinha, N.; Hahn, F. E. Acc. Chem. Res. 2017, 50, 2167; 5) Mata, A. J; Hahn, F. E.; Peris, E. Chem. Sci., 2014, 5, 1723. 6) Nishad, R. C.; Rit, A. Chem. Eur. J. 2021, 27, 594.