All-selenolate-protected eight-electron platinum/silver nanoclusters

Controlled aggregation of Pt/PtH/Rh/RhH doped silver superatomic nanoclusters into 16-electron supermolecules

The assembly of discrete superatomic nanoclusters into larger constructs is a significant stride towards developing a new set of artificial/pseudo-elements. Herein, we describe a novel series of 16-electron supermolecules derived from the combination of discrete 8-electron superatomic synthons containing interstitial hydrides as vertex-sharing building blocks. The symmetric (RhH)2Ag33[S2P(OPr)2]17 (1) and asymmetric PtHPtAg32[S2P(OPr)2]17 (2) are characterized by ESI-MS, SCXRD, NMR, UV-vis absorption spectra, electrochemical and computational methods. Cluster 1 represents the first group 9-doped 16-electron supermolecule, composed of two icosahedral (RhH)@Ag12 8-electron superatoms sharing a silver vertex. Cluster 2 results from the assembly of two distinct icosahedral units, Pt@Ag12, and (PtH)@Ag12. In both cases, the presence of the interstitial hydrides is unprecedented. The stability of the supermolecules is investigated, and 2 spontaneously transforms into Pt2Ag33[S2P(OPr)2]17 (3) with thermal treatment. The lability of the hydride within the icosahedral framework in solution at low-temperature was confirmed by the VT-NMR.

Systematics of stable copper and silver clusters protected by small bite chelating bidentate sulfur and selenium ligands related to their polyhedral cavities: analogies to aliphatic compounds and three-dimensional spherical aromatic systems

Silver and copper clusters capped by external chelating dithiolate ligands can be classified according to the cavities in their central coinage metal polyhedra. Silver clusters composed exclusively of fused tetrahedra are analogous to simple saturated organic compounds. The only interstitial atom that can be fit into an Ag4 tetrahedron is hydrogen. Silver polyhedra with larger trigonal prismatic or cubic cavities, including highly distorted cubic cavities, can accommodate halide and chalcogenide anions. The still larger 12-vertex icosahedral and cuboctahedral coinage metal cavities can accommodate oxoanions of the types SO32- and SO42- and their heavier congeners or alternatively interstitial coinage or platinum group metals leading to central M'@M12 units. Copper clusters with central cuboctahedra and silver clusters with central icosahedra possessing interstitial metal atoms approximate sphericality and provide examples of electron-rich metal superatoms with an average metal oxidation state of less than +1. Such copper cluster superatoms have two extra electrons corresponding to a filled 1S2 superatomic orbital. The silver cluster superatoms are electron richer with eight extra electrons corresponding to filled 1S2 + 1P6 superatomic orbitals. In these silver clusters seven or eight faces of the central Ag12 icosahedron are capped by additional silver atoms in order to provide these additional electrons.

Hydride Doping Effects on the Structure and Properties of Eight-Electron Rh/Ag Superatoms: The [RhHx@Ag21-x{S2P(OnPr)2}12] (x = 0-2) Series

Three hitherto unknown eight-electron rhodium/silver alloy nanoclusters, [RhAg₂₁{S₂P(OⁿPr)₂}₁₂] (1), [RhHAg₂₀{S₂P(OⁿPr)₂}₁₂] (2), and [RhH₂Ag₁₉{S₂P(OⁿPr)₂}₁₂] (3), have been isolated and fully characterized. Cluster 1 contains a regular Rh@Ag₁₂ icosahedral core, whereas 2 and 3 exhibit distorted RhH@Ag₁₂ and RhH₂@Ag₁₂ icosahedral cores. The single-crystal neutron structure of 2 located the encapsulated hydride at the center of an enlarged RhAg₃ tetrahedron. A similar position was found by neutron diffraction for one of the hydrides in 3, whereas the other hydride is trigonally coordinated to Rh and an elongated Ag-Ag edge. The solid-state structures of 1-3 possess C₁ symmetry due to the asymmetric arrangement of the surrounding capping Ag atoms. Our investigation shows that the insertion of one hydride dopant provokes the elimination of one capping silver atom on the cluster surface, resulting in the general formula [RhH_x@Ag_21-x{S₂P(OⁿPr)₂}₁₂] (x = 0-2), which maintains the same number of cluster electrons as well as neutral charge. Clusters 1-3 exhibit an intense emission band in the NIR region. Contrarily to their PdAg₂₁ and PdHAg₂₀ relatives, the 4d orbitals of the encapsulated heterometal are somewhat involved in the optical processes.

Recent progress in dichalcophosphate coinage metal clusters and superatoms

Atomically precise clusters of group 11 metals (Cu, Ag, and Au) attract considerable attention owing to their remarkable structure and fascinating properties. One of the unique subclasses of these clusters is based on dichalcophosphate ligands of [(RO)₂PE₂]^- type (E = S or Se, and R = alkyl). These ligands successfully stabilise the most diverse Cu, Ag, and Au clusters and superatoms, spanning from simple ones to amazing assemblies featuring unusual structural and bonding patterns. It is noteworthy that such complicated clusters are assembled directly from cheap and simple reagents, metal(I) salts and dichalcophosphate anions. This reaction, when performed in the presence of a hydride or other anion sources, or foreign metal ions, results in hydrido- or anion-templated homo- or heteronuclear structures. In this feature article, we survey the recent advances in this exciting field, highlighting the powerful synthetic capabilities of the system "a metal(I) salt - [(RO)₂PX₂]^- ligands - a templating anion or borohydride" as an inexhaustible platform for the creation of new atomically precise clusters, superatoms, and nanoalloys.

DFT Insights into the Variety in the Coordination Modes of the Equatorial Halides in [Au13 Ag12 (PR3 )10 X8 ]+ (X=Cl/Br) Clusters

The bonding character within metal nanoclusters represents an intriguing topic, shedding light on the inherent driving force for the packing preference in nanomaterials. Herein, density functional theory (DFT) calculations were conducted to investigate the correlation of the series of isomeric [Au₁₃ Ag₁₂ (PR₃ )₁₀ X₈ ]⁺ (X=Cl/Br) clusters, which are mainly differentiated by the coordination mode of the equatorial halides (μ₂ -, μ₃ - and μ₄ -) in the rod-like, bi-icosahedral framework. The theoretical simulation corroborates the variety in the configuration of the Au₁₃ Ag₁₂ clusters and elucidates the fast isomerization kinetics among the different configurations. The easy tautomerization and the variety in chloride binding modes correspond to a fluxionality character of the equatorial halides and are verified by the potential energy curve analysis. The structural flexibility of the central Au₃ Ag₁₀ block is the main driving force, while the relatively stronger Ag-X bonding interaction (compared to that of Au-X), and a sufficient number of halides are also requisite for the associating Ag-X tautomerizations.

Surface modifications of eight-electron palladium silver superatomic alloys

Atomically precise thiolate-protected coinage metal nanoclusters and their alloys are far more numerous than their selenium congeners, the synthesis of which remains extremely challenging. Herein, we report the synthesis of a series of atomically defined dithiophosph(in)ate protected eight-electron superatomic palladium silver nanoalloys [PdAg₂₀{S₂PR₂}₁₂], 2a-c (where R = OⁱPr, a; OⁱBu, b; Ph, c) via ligand exchange and/or co-reduction methods. The ligand exchange reaction on [PdAg₂₀{S₂P(OⁿPr)₂}₁₂], 1, with [NH₄{Se₂PR₂}₁₂] (where R = OⁱPr, or OⁿPr) leads to the formation of [PdAg₂₀{Se₂P(OⁱPr)₂}₁₂] (3) and [PdAg₂₀{Se₂P(OⁿPr)₂}₁₂] (4), respectively. Solid state structures of 2a, 2b, 3 and 4 unravel different PdAg₂₀ metal frameworks from their parent cluster, originating from the different distributions of the eight-capping silver(I) atoms around a Pd@Ag₁₂ centered icosahedron with C_2, D_3, T_h and T_h symmetries, respectively. Surprisingly ambient temperature crystallization of the reaction product 3 obtained by the ligand exchange reaction on 1 has resulted in the co-crystallization of two isomers in the unit cell with overall T (3a) and C₃ (3b) symmetries, respectively. To our knowledge, this is the first ever characterized isomeric pair among the selenolate-protected NCs. Density functional theory (DFT) studies further rationalize the preferred geometrical isomerism of the PdAg₂₀ core.

Understanding a ligand's effects on intra-cluster and inter-cluster assembly

Ligands play an essential role in cluster assembly; however, understanding this behavior at the atomic level is far off. In this work, Cd₁₂Ag₃₂(S-PhOMe)₃₆(PPh)₄@Cd₆Ag₂(S-PhOMe)₆Cl₆(PPh₃)₈@Ag₆(S-PhOMe)₆Cl₂ (Abbrev. Cd12Ag32-1) and Cd₁₂Ag₃₂(S-c-C₆H₁₁)₃₆ (Abbrev. Cd12Ag32-2) were synthesized and structurally determined by single-crystal X-ray diffraction. An important finding is the selective adsorption of phosphine ligands that is caused by the different types of thiol ligands. In addition, Cd12Ag32-1 follows a unique stacking pattern in a superlattice with multiple inter-cluster channels. Overall, this study is helpful for an in-depth understanding of the effect of mixed ligands on nanocluster formation and the correlation between structure and properties in the nanocluster range.

Hydride-Containing Eight-Electron Pt/Ag Superatoms: Structure, Bonding, and Multi-NMR Studies

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(OⁿPr)₂, 1; dsep = Se₂P(OⁱPr)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, C₁ and C₃, respectively. Whereas the multi-NMR spectra of 2 in solution at 173 K reveal that the structure of C₃ symmetry is the predominant one, ¹H and ¹⁹⁵Pt NMR spectra of 1 at the same temperature disclose the presence of isomers of both C₁ and C₃ 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 5d_z²(Pt) orbital.

Silver(I) and Gold(I) Monothiocarbonate Complexes: Synthesis, Structure, Luminescence

The monothiocarbonate ligand, [S(O)COR]−, is unusual and rare regarding its use in the formation of coordination compounds. Here, we report the synthesis and structures of the silver(I) and gold(I) monothiocarbonate complexes, [{Ag4(SC(O)OiPr)2(2,2′-bpy)4}(PF6)2]n (1) and [Au2{S(O)COiPr}2(dppe)]n (2), respectively. Both complexes are coordination polymers, with 1 being cationic and 2 neutral. The uniqueness of the ligand is that it is monoanionic and contains both a ‘hard’ O-donor ligand and a ‘soft’ S-donor ligand in a O-C-S manifold with, in principle, electron delocalization across the three atoms. However, for both complexes 1 and 2, it was found that the binding occurred exclusively through the S-donor atom, while the C=O portion remained dangling and was not involved in bonding. This bonding mode departs significantly from the symmetrical S-C-S type ligand such as dithiocarbamates. The structures were analysed and confirmed by NMR and X-ray crystallography.

Alloying dichalcogenolate-protected Ag21 eight-electron nanoclusters: a DFT investigation

The isoelectronic doping of dichalcogenolato nanoclusters of the type [Ag₂₁{E₂P(OR)₂}₁₂]⁺ (E = S, Se) by any heteroatom belonging to groups 9-12 was systematically investigated using DFT calculations. Although they can differ in their global structure, all of these species have the same M@M₁₂-centered icosahedral core. In any case, the different structure types are all very close in energy. In all of them, three different alloying sites can be identified (central, icosahedral, peripheral) and calculations allowed the trends in heteroatom site occupation preference across the group 9-12 family to be revealed. These trends are supported by complementary experimental results. They were rationalized on the basis of electronegativity, potential involvement in the bonding of valence d-orbitals and atom size. TD-DFT calculations showed that the effect of doping on optical properties is sizable and this should stimulate research on the modulation of luminescence properties in the dithiolato and diseleno families of complexes.

Mass spectrometry guided surface modification of a tellurate ion templated 36-nucleus silver alkynyl nanocluster

Under the guidance of the ESI-MS result for [TeO6@Ag36(CCtBu)18(tfa)12] (1, tfa = trifluoroacetate), a new 36-nucleus silver-alkynyl cluster substituted by four pentafluorobenzoates, named as [TeO6@Ag36(CCtBu)18(tfa)8(F5PhCO2)4] (2), has been fabricated.