Insertion of a Hydride Ion Into a Tetrasilver(I) Cluster Covered by S-Donating Rhodium(III) Metalloligands.

Here, we report a tetrahedral silver(I) cluster of {Ag} covered by Δ-[Rh(l-cys)] (l-Hcys = l-cysteine), which is converted to an {AgH} cluster via the inclusion of a H ion. The 1:1 reaction of Δ-[Rh(l-cys)] with Ag gave a sulfur-bridged AgRh octanuclear structure in [Ag{Rh(l-cys)}] ([]), in which a tetrahedral {Ag} core is bound by four Δ-[Rh(l-cys)] units through thiolato groups. DFT calculations revealed that a superatomic orbital exists in {Ag} as the lowest unoccupied molecular orbital, contributing to the appearance of a characteristic charge-transfer transition in the visible region for []. Treatment of [] with NaBH led to the insertion of a H ion to generate [AgH{Rh(l-cys)}] ([]) with an {AgH} core, accompanied by the disappearance of the visible band for []. The presence of a H ion in the center of [] was established by the H NMR spectrum, which reveals a unique quintuple-quintet signal from the H ion surrounded by four Ag atoms. [] was considerably stable in aqueous media, which is ascribed to a chemical bond between the unoccupied superatomic orbital of {Ag} and the occupied orbital of H in the {AgH} core.