[Ag7(H){S2CC(CN)2}6]6-: An Anionic Heptanuclear Silver Hydride Cluster Compound Stabilized by Dithiolate Ligands

In our attempts to identify probable intermediates in the preparation of anionic silver hydride cluster [Ag-8(H){S2CC(CN)(2)}(6)](5-) under the condition of excess NaBH4, we isolated and analyzed a new cluster compound, namely, [Bu4N](6)[Ag-7(H){S2CC(CN)(2)}(6)]. We report here the synthesis, crystal structure, characterizations by various spectroscopic (UV-Vis, IR, multinuclear NMR, elemental analyses) techniques and the luminescent properties of this cluster. Its X-ray crystal structure reveals that the cluster contains a distorted; tricapped tetrahedral silver core enclosed an interstitial hydride anion and is surrounded by six 1,1-dicyanoethylene-2,2-dithiolate ([S2CC(CN)(2)](2-), i-MNT) ligands. The presence of hydride inside the heptanuclear silver cluster is unequivocally certified by both H-1 and Ag-109 NMR spectroscopies. The title compound represents the first atomic precisely anionic Ag-7-H skeleton with a non-disordered, tricapped tetrahedral silver framework.