N-heterocyclic carbenes as effective ligands for the preparation of stabilized copper- and silver-t-butylthiolate clusters†
Abstract
The ligation of N-heterocyclic carbenes (NHCs) to [CuStBu] and [AgStBu] was developed as an alternative to PR3 ligands as solubilizing reagents for these coordination polymers in order to form polynuclear copper and silver t-butylthiolate clusters. 1,3-Di-isopropylbenzimidazol-2-ylidene (iPr2-bimy) and 1,3-di-isopropyl-4,5-dimethylimidazol-2-ylidene (iPr2-mimy) were ligated to [CuStBu] and [AgStBu] forming [Cu4(StBu)4(iPr2-bimy)2] 1, [Cu4(StBu)4(iPr2-mimy)2] 2, [Ag4(StBu)4(iPr2-bimy)2] 5 and [Ag5(StBu)6][Ag(iPr2-mimy)2] 6. For comparison, the trialkyl phosphines PnPr3 and PiPr3 were also used to solubilize [AgStBu] and [CuStBu] to form copper and silver t-butylthiolate clusters. [Cu4(StBu)4(PnPr3)2] 3, [Cu4(StBu)4(PiPr3)2] 4, [Ag4(StBu)4(PnPr3)2] 7 and [Ag6(StBu)6(PiPr3)2] 8 were thus formed upon reaction with [CuStBu] and [AgStBu]. The synthesized complexes have been characterized via spectroscopic and crystallographic methods. The molecular structures of the clusters, which can vary according to the ligand type, are described.