Isolation of Homo-/Mixed-Valence Ag , Ag , and Ag Clusters Stabilized by Cyclic Alkyl(amino) Carbene-Anchored Monoanionic Phosphorus Ligand.

Silver clusters are attractive candidates for their promising optical properties, and biomedical activities. Herein, we report on the first syntheses and isolation of three homo-/mixed-valence silver nanoclusters (NCs) with Ag Cl , Ag , and Ag cores ((cAAC)P) Ag Cl (1), [((cAAC)P) Ag ] (2), and [((cAAC)P) Ag ] (3) having three-/twofold symmetry, employing cyclic alkyl(amino) carbene (cAAC)-supported phosphinidenide (cAACP ) as the π-accepting stabilizing ligand. The average diameters of Ag NCs 1, and 2 are approximately 1.6 to 2 nm. The redox non-innocent mono-atomic phosphorus anions (P ) anchored with cAAC ligands are generated in situ by the reaction of AgOTf with a boryl-phosphaalkene (cAAC)P-B(N Pr ) through cleavage of the P-B bond with the help of a triflate anion (OTf ) as a weak nucleophile. Equivalent number of the (cAAC)P anions generated in situ are oxidized to produce the corresponding bis-phosphinidene (cAAC) P leading to the generation of Ag ions in solution for the formation of the unprecedented mixed-valence Ag NC 2. Complex 3 is achieved by treating potassium phosphinidenide cAACPK with AgNTf . The ligand field and the steric hindrance of the (cAAC)P units play crucial roles in stabilizing complexes 1-3, further providing a three- (1, 2)/two- (3) fold stand. The Ag Cl NC (1) with a tricationic core [Ag Cl ] was found to be diamagnetic, and fluorescent, emitting green light at 563 nm when excited at 400 nm. In contrast, the neutral Ag (2) and Ag (3) clusters were found to be paramagnetic, and NMR silent showing characteristic EPR signals for Ag at room temperature.