Isolation of Homo-/Mixed-Valence Ag 12 , Ag 29 , and Ag 8 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 12 Cl 3 , Ag 29 , and Ag 8 cores [((cAAC)P) 6 Ag 12 Cl 3 ](OTf) 3 (1), [((cAAC)P) 6 Ag 29 ] (2), and [((cAAC)P) 4 Ag 8 ] (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 i Pr 2 ) 2 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) 2 P 2 leading to the generation of Ag 0 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 2 . 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 12 Cl 3 NC (1) with a tricationic core [Ag I 12 Cl 3 ] was found to be diamagnetic, and fluorescent, emitting green light at 563 nm when excited at 400 nm. In contrast, the neutral Ag 29 (2) and Ag 8 (3) clusters were found to be paramagnetic, and NMR silent showing characteristic EPR signals for Ag 0 at room temperature.