Driving Diverse Bond Functionalisation with N-Heterocyclic Silylene-Coinage Metal-Aryl Complexes

Abstract

Anchoring homolytic and heterolytic bond functionalisation at low-coordinate coinage metal centres is important due to their potential use as active catalysts in organic transformations. In the realm of carbene-stabilised coinage metal chemistry, heteroatom functionalised coinage metal precursors synthesised from such bond activations have long been explored. Interestingly, N-heterocyclic silylene, being equally potent neutral donor ligands, has not been used for the same. Of note, carbene-stabilised heteroatom functionalised coinage metal precursors are vastly developed with copper centres only, while silver has been underexplored. This work reports the isolation of a variety of [PhC{N(tBu)}2SiN(SiMe3)2] (1) coordinated aryl-copper(I) and aryl-silver(I) complexes (2-8). We have also examined the reactivity pattern of organo-copper with differently substituted silylenes (9-11). These complexes were then utilised to cleave various homolytic and heterolytic bonds to access silylene-coordinated heteroatom functionalised coinage metal complexes (12-24). We have shown the reaction of reactive aryl-coinage metal precursors towards homolytic bonds, having B–B and Se–Se bonds, which led to the formation of NHSi-supported dimeric µ-boryl bound Cu(I) complex (12) and a new class of unprecedented NHSi-supported coinage metal-selenogenolates (14-16). These aryl-coinage metal precursors also smoothly afforded several elusive NHSi-copper and silver amides (17-22) via N–H bond cleavage. A heterolytic cleavage of the P–Si bond resulted in the formation of NHSi stabilised copper and silver phosphide complexes (23 and 24), among which the latter is the first precedent of the dimeric Ag-phosphide complex. Lastly, we have utilised NHSi→copper–aryl complexes as aryl transfer reagents in C–C coupling reactions, which led to the formation of products in excellent yields with high TON. The analogous silver complex was employed in the three-component α-aminonitrile synthesis efficiently. Our report establishes that NHSi coordinated aryl copper and silver complexes as the perfect and robust platform for accessing a diverse array of reactive coinage metal precursors that were hitherto unknown.