Silver(I) Clusters with Carba-closo-dodecaboranylethynyl Ligands: Synthesis, Structure, and Phosphorescence.

Salts of anionic silver(I) clusters with the carba-closo-dodecaboranylethynyl ligand were obtained from {Ag (12-C≡C-closo-1-CB H )} , selected pyridines, and [Et N]Cl or [Ph P]Br. Salts of octahedral silver(I) clusters [Et N] [Ag (12-C≡C-closo-1-CB H ) (4-X-C H N) ] were formed with pyridine (X=H, x=8), 4-methylpyridine (X=Me, x=8), and 4-cyanopyridine (X=CN, x=10). In contrast, 3,5-lutidine (3,5-Me Py) did not result in salts of dianionic clusters, even in the presence of excess of [Et N]Cl or [Ph P]Br; instead salts of monoanionic Ag clusters, [Et N][Ag (12-C≡C-closo-1-CB H ) (3,5-Me Py) ] and [Ph P][Ag (12-C≡C-closo-1-CB H ) (3,5-Me Py) ] were obtained. The Ag cluster is pentagonal bipyramidal in the former, but is an edge-capped octahedron in the latter. The 4-methylpyridine and 3,5-lutidine complexes show green phosphorescence at room temperature. Although argentophilic interactions give rise to sufficient spin-orbit coupling for intersystem crossing S →T and moderate-to-high radiative rate constants, time-resolved measurements indicate that the quantum yields are greatly influenced by the pyridine ligands, which mainly determine the non-radiative rate constants. In addition, the crystal structures of [Ag (12-C≡C-closo-1-CB H ) (Py) (CH CN) (CH Cl ) ]⋅CH Cl , [Ag (12-C≡C-closo-1-CB H ) (Py) ], [Ag (12-C≡C-closo-1-CB H ) (4-MePy) Br ], [Ag (12-C≡C-closo-1-CB H ) (4-tBuPy) Cl]⋅(4-tBuPy), and [Ag (12-C≡C-closo-1-CB H ) (3,5-Me Py) Cl] were elucidated.