Stable Silver(I) Hydride Complexes Supported by Diselenophosphate Ligands

The first stable structure of silver(I) cluster cations [Ag8(μ4−H){Se2P(OR)2}6]+ [R = iPr, 1; Et, 2] containing Ag(I)-hydride bridges (Ag−μ-H−Ag) in T symmetry was reported. The clusters having an interstitial hydride were composed of an octanuclear silver core in tetracapped tetrahedral geometry, which was inscribed within a Se12 icosahedron represented by six dialkyl diselenophosphate ligands in a tetrametallic-tetraconnective (μ2, μ2) bonding mode. The presence of hydride was unequivocally corroborated by both 1H and 109Ag NMR spectroscopies of which a nonet in the 1H NMR spectrum for the hydride resonance coupled with a doublet peak observed in the 109Ag NMR spectrum clearly suggests that eight silver nuclei are equivalent in the NMR time scale and a fast exchange of the positions between the vertex and capping silver atoms in solution must occur. The hypothesis was also supported by a density functional theory (DFT) investigation on a simplified model [Ag8(H)(Se2PH2)6]+, which confirmed that the Ag8H cubic core of Th symmetry may not be formed as it is energetically highly unfavorable (0.67 eV less stable than the T structure).