## 1 Introduction  
Despite their efficiency and selectivity, most homogeneous transition metal catalysts have seen limited industrial use due to challenges with their recycling and the risk of metal contamination in the final products. In contrast, heterogeneous catalysis simplifies separation and recycling, making it more advantageous for industrial applications. The strong N-heterocyclic carbene (NHC)-metal bonds arising from the unique \(\sigma\)-donating and weak \(\pi\)-accepting properties of the carbene centers enhance the stability of NHC-metal catalysts by preventing their decomposition [1, 2, 3, 4, 5, 6, 7, 8, 9]. As a result, the NHC system is a highly attractive choice for heterogeneous catalysis applications [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32]. Since the development of various organic-group-functionalized polymers, such as the widely known Merrifield resin, solid-phase synthesis has been recognized as a valuable tool. Merrifield resin contains chloromethyl groups, which react with substituted azoles to form polymer-supported azolium chloride. To date, several NHC-metal catalysts anchored on Merrifield resin have been developed and successfully used in catalytic transformations (Figure 1). In 2004, [PERSON] demonstrated a polymer-supported NHC-Pd catalyst of the Suzuki cross-coupling reaction between phenylboronic acid and aryl halides [33, 34]. The addition reaction of phenylboronic acid to aromatic aldehydes was achieved using an NHC-Rh catalyst under heterogeneous conditions [35]. Additionally, polymer-linked NHC-metal species have been applied to the three-component coupling reaction of alkynes, amines, and aldehydes, as well as to the hydroformination of alkenes and Heck-type reactions [36, 37, 38, 39]. More recently, an alkyl-bridged bis(NHC)-Pd complex anchored on Merrifield resin was developed for the synthesis of alkynes through the reaction of alkynes, aryl iodides, and CO [40]. Meanwhile, studies have reported the coupling reaction of optically active azoles with Merrifield resin, yielding azolium salts with a chiral carbon center [41]. However,no reports have yet described catalytic asymmetric reactions using polymer-supported NHC-metal complexes derived from Merrifield resin. Recently, we synthesized a new class of azolium compound **L1** as a chiral NHC precursor (Figure 2). We developed two methods for Ir-catalyzed asymmetric ketone reduction using (EtO)\({}_{2}\)MeSiH and **L1**. First, a well-defined NHC-Ir complex was successfully synthesized via the formation of an intermediate NHC-Ag complex from the reaction of **L1** with Ag\({}_{2}\)O (Figure 2a). The resulting IrCl(NHC)(cod) complex was fully characterized by NMR and an elemental analysis. Notably, IrCl(NHC)(cod) efficiently catalyzed the enantioselective hydrosilylation of ketones with (EtO)\({}_{2}\)MeSiH, yielding corresponding optically active alcohols (Figure 2a) [42; 43; 44]. Second, we demonstrated an operationally simple procedure using [Ir(cod)\({}_{2}\)]BF\({}_{4}\) or [Ir(OHe)(cod)]\({}_{2}\) as an Ir precursor (Figure 2b). The combination of the Ir precursor and **L1** efficiently facilitated the silane reduction of ketones with high enantioselectivity. In this method, the Ir precursor, **L1**, and (EtO)\({}_{2}\)MeSiH were first combined in THF, after which the ketone was introduced into the resulting mixture, which was placed in MeOH containing a small amount of K\({}_{2}\)CO\({}_{3}\). This _pre-mixing_ reaction procedure proceeded at room temperature for 2 h, yielding a corresponding alcohol with up to 95% ee (Figure 2b) [45; 46; 47]. As shown in Figure 2b, we were surprised to find that replacing the benzyl substituent (**L1**) with a methyl substituent (**L2**) at the azolium ring substantially reduced both the product yield and enantioselectivity [47].