Soluble Silver Acetylide for the Construction and Structural Conversion of All-Alkynyl-Stabilized High-Nuclearity Homoleptic Silver Clusters

Silver acetylide complex [Ag­(ArCC)]<sub><i>n</i></sub> (Ar = 3,5-di-<i>tert</i>-butylphenyl) with unprecedented high solubility in common organic solvents has been designed and synthesized. The high solubility is due to two bulky <i>tert</i>-butyl substituents on the phenyl ring. This feature is significant to construct and isolate single crystals of all-alkynyl-stabilized silver clusters, which are crucial to investigate the intrinsic binding interaction and coordination modes between Ag­(I) and ethynide ligands. Crystallization of [Ag­(ArCC)]<sub><i>n</i></sub> under various conditions resulted in three high-nuclearity homoleptic silver acetylide clusters, namely, [Ag<sub>21</sub>(ArCC)<sub>20</sub>]­(OH) (<b>1</b>), [Ag<sub>16</sub>(ArCC)<sub>16</sub>] (<b>2</b>), and [Ag<sub>15</sub>(ArCC)<sub>15</sub>] (<b>3</b>). Complex <b>1</b> has a [Ag<sub>21</sub>] cluster protected by twenty 3,5-di-<i>tert</i>-butyl-phenylethynide ligands. Complexes <b>2</b> and <b>3</b> have neutral [Ag<sub>16</sub>] and [Ag<sub>15</sub>] clusters, respectively. In addition to these homoleptic silver clusters, two new silver acetylides [Ag<sub>20</sub>(ArCC)<sub>16</sub>(CH<sub>3</sub>COO)<sub>4</sub>] (<b>4</b>) and [Ag<sub>22</sub>(ArCC)<sub>16</sub>(NO<sub>3</sub>)<sub>4</sub>(CH<sub>3</sub>CH<sub>2</sub>OH)<sub>4</sub>]­(OH)<sub>2</sub> (<b>5</b>) were synthesized. The acetate and nitrate anions in these structures are more like counterions instead of acting as critical building blocks or templates for cluster assembly. These results illustrated the significance of 3,5-di-<i>tert</i>-butyl-phenylethynide ligands in the construction and stabilization of high-nuclearity silver clusters. Analysis of structures of <b>1</b>–<b>5</b> revealed several novel coordination modes between Ag­(I) and ethynide ligands, which contributed considerably to our knowledge of Ag­(I)–ethynide binding interactions.