Silver(I)–NHC complexes with chalcogenocyanate ligands: synthesis and transfer reactivity

Abstract The chemistry of N-heterocyclic carbene (NHC) silver(I) complexes has been studied for over 30 years, mainly focusing on halide species, in part due to their ability to act as NHC-transfer reagents. This study reports the first examples of silver(I)–NHC cyanate complexes, Ag(NHC)(NCO), with 6 complexes synthesized via 2 complementary methods. The progression to the heavier chalcogenocyanate ligands, thiocyanate and selenocyanate, presents a more complex scenario. The corresponding reactions with thiocyanate salts produce ionic products composed of Ag(NHC)2+ and a thiocyanate-containing anion, when the NHC ligands employed are IMes, IXy, SIXy, or IMesBr. In contrast, the deployment of the bulkier SIPr ligand results exclusively in the isolation of the neutral species Ag(SIPr)(SCN). Reactions with potassium selenocyanate lead to degradation, preventing the isolation of any selenocyanate-containing species. Finally, both cyanate and thiocyanate complexes successfully transferred NHC and chalcogenocyanate ligands to gold(I), indicating their versatility as transfer agents.