Recent reports on hydride-doped noble metal nanoclusters strongly suggest that the encapsulated hydride is a part of the superatom core, but no accurate location of the hydride could be experimentally proved, so far. We report herein a hydride-doped eight-electron platinum/silver alloy nanocluster in which the position of four-coordinated hydride was determined by neutron diffraction for the first time. X-ray structures of [PtHAg19(dtp/desp)12] (dtp = S2P­(O n Pr)2, 1; dsep = Se2P­(O i Pr)2, 2) describe a central platinum hydride (PtH) unit encapsulated within a distorted Ag12 icosahedron, the resulting (PtH)@Ag12 core being stabilized by an outer sphere made up of 7 capping silver atoms and 12 dichalcogenolates. Solid-state structures of 1 and 2 differ somewhat in the spatial configuration of their outer spheres, resulting in overall different symmetries, C 1 and C 3, respectively. Whereas the multi-NMR spectra of 2 in solution at 173 K reveal that the structure of C 3 symmetry is the predominant one, 1H and 195Pt NMR spectra of 1 at the same temperature disclose the presence of isomers of both C 1 and C 3 symmetry. DFT calculations found both isomers to be very close in energy, supporting the fact that they co-exist in solution. They also show that the [PtH@Ag12]5+ kernel can be viewed as a closed-shell superatomic core, the μ4-hydride electron contributing to its eight-electron count. On the other hand, the 1s­(H) orbital contributes only moderately to the superatomic orbitals, being mainly involved in the building of a Pt–H bonding electron pair with the 5dz 2(Pt) orbital.

The first 8-electron Pd/Ag superatomic alloys with an interstitial hydride [PdHAg 19 (dtp) 12 ] (dtp = S 2 P(O i Pr) 2 À ) 1 and [PdHAg 20 (dtp) 12 ] + 2 are reported. The targeted addition of a single Ag atom to 1 is achieved by the reaction of one equivalent of trifluoroacetic acid, resulting in the formation of 2 in 55 % yield. Further modification of the shell results in the formation of [PdAg 21 (dtp) 12 ] + 3 via an internal redox reaction, with the system retaining an 8-electron superatomic configuration. The interstitial hydride in 1 and 2 contributes its 1s 1 electron to the superatomic electron count and occupies a PdAg 3 tetrahedron. The distributions of isomers corresponding to different dispositions of the outer capping Ag atoms are investigated by multinuclear VT NMR spectroscopy. The emissive state of 3 has a lifetime of 200 μs (λ ex = 448; λ em = 842), while 1 and 2 are non-emissive. The catalytic reduction of 4-nitrophenol is demonstrated with 1-3 at room temperature.

The first stable structure of silver(I) cluster cations [Ag(8)(mu(4)-H){Se(2)P(OR)(2)}(6)](+) [R = (i)Pr, 1; Et, 2] containing Ag(I)-hydride bridges (Ag-mu-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 Se(12) icosahedron represented by six dialkyl diselenophosphate ligands in a tetrametallic-tetraconnective (mu(2), mu(2)) bonding mode. The presence of hydride was unequivocally corroborated by both (1)H and (109)Ag NMR spectroscopies of which a nonet in the (1)H NMR spectrum for the hydride resonance coupled with a doublet peak observed in the (109)Ag 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 [Ag(8)(H)(Se(2)PH(2))(6)](+), which confirmed that the Ag(8)H cubic core of T(h) symmetry may not be formed as it is energetically highly unfavorable (0.67 eV less stable than the T structure).

The hydrido copper(I) and silver(I) clusters incorporating 1,1-dicyanoethylene-2,2-dithiolate (i-MNT) ligands are presented in this paper. Reactions of M(I) (M = Cu, Ag) salts, [Bu(4)N](2)[S(2)CC(CN)(2)], with the anion sources ([Bu(4)N][BH(4)] for H(-), [Bu(4)N][BD(4)] for D(-)) in an 8:6:1 molar ratio in THF produce octanuclear penta-anionic Cu(I)/Ag(I) clusters, [Bu(4)N](5)[M(8)(X){S(2)CC(CN)(2)}(6)] (M = Cu, X = H, 1(H); X = D, 1(D); M = Ag, X = H, 2(H); X = D, 2(D)). They can also be produced from the stoichiometric reaction of M(8)(i-MNT)(6)(4-) with the ammonium borohydride. All four compounds have been fully characterized spectroscopically ((1)H and (13)C NMR, IR, UV-vis) and by elemental analyses. The deuteride-encapsulated Cu(8)/Ag(8) clusters of 1(D) and 2(D) are also characterized by (2)H NMR. X-ray crystal structures of 1(H) and 2(H) reveal a hydride-centered tetracapped tetrahedral Cu(8)/Ag(8) core, which is inscribed within an S(12) icosahedron formed by six i-MNT ligands, each in a tetrametallic-tetraconnective (μ(2), μ(2)) bonding mode. The encapsulated hydride in 2(H) is unequivocally characterized by both (1)H and (109)Ag NMR spectroscopies, and the results strongly suggest that the hydride is coupled to eight magnetically equivalent silver nuclei on the NMR time scale. Therefore, a fast interchange between the vertex and capping silver atoms in solution gives a plausible explanation for the perceived structural differences between the Ag(8) geometry deduced from the X-ray structure and the NMR spectra.

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In sharp contrast to that of surface hydrides, reactivities on interstitial hydrides are difficult to explore. When treated with a metal ion (Cu + , Ag + , and Au + ), the stable Cu(I) dihydride template [Cu11H2{S2P(O i Pr)2}6(C≡CPh)3] (H2Cu11) generates surprisingly three very different compounds; namely(2), and [AuCu11{S2P(O i Pr)2}6(C≡CPh)3Cl] (3). 1 and 2 are both M(I) species and maintain the same number of hydride ligands as their H2Cu11 precursor. Neutron diffraction revealed the first time a trigonal pyramidal hydride coordination mode in an AgCu3 environment of 2. The bimetallic cluster of 3 has no hydride and exhibits a mixed-valent [AuCu11] 10+ metal core, making it a 2-electron superatom. Thus, depending on the nature of M + , trigonal pyramidal hydrides of the H2Cu11 reactant behave differently. In the cases of M = Cu or Ag, they act as regular 2-electron ligands. In the case of M = Au, they behave as electron donors, leading to the formation of a 2-electron superatom, with liberation of H2.. .

In sharp contrast to surface hydrides,r eactivities of interstitial hydrides are difficult to explore.W hen treated with am etal ion (Cu + ,A g + ,a nd Au + ), the stable Cu I dihydride template [Cu 11 H 2 {S 2 P(O i Pr) 2 } 6 (C CPh) 3 ]( H 2 Cu 11 )g enerates surprisingly three very different compounds,n amely [CuH 2 Cu 11 {S 2 P(O i Pr) 2 } 6 (C CPh) 3 ] + (1), [AgH 2 Cu 14 {S 2 P-(O i Pr) 2 } 6 ((CCPh) 6 ] + (2), and [AuCu 11 {S 2 P(O i Pr) 2 } 6 (C CPh) 3 Cl] (3). Compounds 1 and 2 are both M I species and maintain the same number of hydride ligands as their H 2 Cu 11 precursor.Neutron diffraction revealed the first time atrigonalpyramidal hydride coordination mode in the AgCu 3 environment of 2. 3 has no hydride and exhibits am ixed-valent [AuCu 11 ] 10+ metal core,m aking it at wo-electron superatom.

Two mixed-metal hydride clusters abbreviated as Cu3Ag4H and Cu4Ag3H were structurally characterized from a set of atomically precise heptanuclear clusters, CuxAg7-x(H){S2P(OiPr)2}6 (x = 1-6) synthesized via a one-pot reaction. An...