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A low-valent Ga(i) complex, [Ga@Bi10(NbMes)2]3−, with a linear Nb–Ga–Nb fragment was synthesized by the reaction of K5Ga2Bi4 with NbMes2. This unusual Zintl cluster represents the first compound with Nb–Ga and Nb–Bi bonds.

We report here the structure of an endohedral plumbaspherene, [Cu4Pb22]4–, the gold analogue of which was previously postulated to be a “missing link” in the growth of larger clusters containing three and four icosahedral subunits. The cluster contains two [Cu2Pb11]2–subunits linked through a Cu2Pb4trigonal antiprism. Density functional theory reveals that the striking ability of mixed Pb/coinage metal Zintl clusters to oligomerize and, in the case of Au, to act as a site of nucleation for additional metal atoms, is a direct consequence of theirnd10(n+ 1)s0configuration, which generates both a low-lying (n+ 1)s-based LUMO and also a high-lying Pb-centered HOMO. Cluster growth and nucleation is then driven by this amphoteric character, allowing the clusters to form donor–acceptor interactions between adjacent icosahedral units or to additional metal atoms.

We report the first disubstituted hetero-ten-vertex closo cluster [(CrGe9)Cr2(CO)13]4− with three adjacent Cr(CO)n units adopting both η5 and η1 coordination modes, which was synthesized through the reaction of “KGe1.67” with (MeCN)3Cr(CO)3 and Cr(CO)6 in ethylenediamine (en) solution. In contrast to the η1-Cr atoms forming localized two-center two-elelctron (2c-2e) Cr-Ge bonds, the hetero atom η5-Cr exhibits versatile bonding mechanisms including three 5c-2e and five 8c-2e delocalized bonds which account for Huckel aromaticity. Intricate multi-center bonding patterns delineate the multiple local σ-aromatic characters of the title cluster displaying explicit spherical aromaticity.

The ternary Ge cluster [Co2@(Ge17Ni)]4− was synthesized, which not only exhibits a unique double-cage form in the family of 18-vertex Zintl clusters, but also makes up the missing link of edge fusion in the construction of double-cage systems.

The continuous pure tin nanorod assembly species Sn368− was isolated in the solid-state and verified by experiments and calculations.

Group 14 Zintl anions [Ex]q−(E = Si–Pb,x= 4, 5, 9, 10) are synthetically accessible, and their diverse chemical reactivity makes them valuable synthons in the construction of larger nanoclusters with remarkable structures, intriguing patterns of chemical bonding, and tunable physical and chemical properties. A plethora of novel cluster anions have now been isolated from the reactions of polyanionic [Ex]q−precursors with low-valent d-/f-block metal complexes, main-group organometallics, or organics in polar aprotic solvents. The range of products includes intermetalloid clusters with transition metal atom(s) embedded in main-group element cages, organometallic Zintl anions in which [Ex]q−acts as a ligand, intermetallic Zintl anions where [Ex]q−is bridged by ligand-free transition metal atom(s), organo-Zintl anions where [Ex]q−is functionalized with organic-group(s), and oligomers formed through oxidative coupling reactions. The synthesis and characterization of these unconventional complexes, where important contributions to stability come from ionic, covalent, and metal–metal bonds as well as weaker aurophilic and van der Waals interactions, extend the boundaries of coordination chemistry and solid-state chemistry. Substantial progress has been made in this field over the past two decades, but there are still many mysteries to unravel related to the cluster growth mechanism and the controllable synthesis of targeted clusters, along with the remarkable and diverse patterns of chemical bonding that present a substantial challenge to theory. In this Account, we hope to shed some light on the relationship between structure, electronic properties, and cluster growth by highlighting selected examples from our recent work on homoatomic deltahedral [Ex]q−anions, including (1) germanium-based Zintl clusters, such as the supertetrahedral intermetallic clusters [M6Ge16]4–(M = Zn, Cd) and the sandwich cluster {(Ge9)2[η6-Ge(PdPPh3)3]}4–with a heterometallicGe@Pd3interlayer; (2) tin-based intermetalloid clusters [Mx@Sny]q−and the application of [Co@Sn9]4–in bottom-up synthesis; and (3) lead clusters with precious metal cores, including the largest Zintl anion [Au12Pb44]8–. In addition to their intrinsic appeal from a structural and electronic perspective, these new cluster anions also show promise as precursors for the development of new materials with applications in heterogeneous catalysis, where we have recently reported the selective reduction of CO2.

The anionic cluster [Fe2@Ge16]4–has been characterized and shown to be isostructural to the knownD2h-symmetric α isomer of the cobalt analogue [Co2@Ge16]4–. Together with the known pair of compounds [Co@Ge10]3–and [Fe@Ge10]3–, the title compound completes a set of four closely related germanium clusters that allow us to explore how the metal–metal and metal–cage interactions evolve as a function of size and of the identity of the metal. The results of spin-unrestricted density functional theory (DFT) and multiconfigurational self-consistent field (MC-SCF) calculations present a consistent picture of the electronic structure where transfer of electron density from the metal to the cage is significant, particularly in the Fe clusters where the exchange stabilization of unpaired spin density is an important driving force.

During the past two decades, single-atom-centered medium-sized germanium clusters [M@Ge

In this work, we synthesize naked tin cluster anion Sn

Since [Sn8 ]6- was discovered from the solid-state phase in 2000, its solution chemistry has been elusive due to the high charges and chemical activity. Herein, we report the synthesis and characterization of an inverse sandwich-type cluster dimer {[K2 ZnSn8 (ZnMes)]2 }4- (1 a), in which the highly charged [Sn8 ]6- is captured by mixed-valence ZnI /ZnII to form the dimer {closo-[Zn2 Sn8 ]}2 moieties bridged by a Zn-Zn bond. Such Zn-Sn cluster not only exhibits a novel example of mixed-valence ZnI /ZnII for stabilizing highly active anion species, but also indicates the [Sn8 ]6- cluster can act as a novel bridging ligand, like arene, with a η4 :η4 -fashion. Theoretical calculations indicate that a significant delocalization of electrons over Zn atoms plays a vital role in the stabilization of the [Sn8 ]6- species. The AdNDP and magnetic response analyses clearly showed the presence of local σ-aromaticity in three cluster fragments: two ZnSn4 caps and Sn8 square antiprism.

Density functional theory (DFT) calculations were employed to study the stabilities, electronic structures, and vibrational and bonding properties of dianionic pentacarbonyls [TM(CO)5]2- (TM = Cr, Mo, W). A D3h symmetry structure with singlet state was found to be the ground state and C-O stretching vibrational frequencies range from 1719 to 1766 cm-1, which are in excellent agreement with the experimental observations. The calculation results on bond dissociation energy for the CO loss revealed their stabilities. By employing energy decomposition analysis (EDA), the bonding nature between TM2- and (CO)5 was disclosed, in which the [TM(d)]2-→(CO)5π backdonations contribute largely to the orbital interactions while σ donation from the lone pair of CO to metal contributes moderately. Compared with those in the isoelectronic neutral hexacarbonyls TM(CO)6, the π backdonations are obviously larger in [TM(CO)5]2- because there are two extra electrons in (n- 1)d AOs of the center transition metal.

The first Zintl cluster containing a distorted Bi6 triangular prism, [Bi6Mo3(CO)9]4-, has been synthesized and structurally characterized. Quantum chemical calculations indicated that the distorted cage cluster features multiple local σ-aromaticity.

We report here the structure of an endohedral plumbaspherene, [Cu

The development of rational synthetic routes to inorganic arsenide compounds is an important goal because these materials are finding applications in many areas of materials science. In this paper, we show that the binary crown clusters [M@As

The [Nb@As

We report here a new double-cage endohedral Ge cluster, [Co

Sandwich-type clusters with the planar fragment containing a heterometallic sheet have remained elusive. In this work, we introduce the [K(2,2,2-crypt)]4{(Ge9)2[η6-Ge(PdPPh3)3]} complex that contains a heterometallic sandwich fragment. The title compound is structurally characterized by means of single-crystal X-ray diffraction, which reveals the presence of an unusual heteroatomic metal planar fragment Ge@Pd3. The planar fragment contains a rare formal zerovalent germanium core and a peculiar bonding mode of sp2-Ge@(PdPPh3)3 trigonal planar structure, whereas the nonagermanide fragments act as capping ligands. The chemical bonding pattern of the planar fragment consists of three 2c-2e Pd-Ge σ-bonds attaching Pd atoms to the core Ge atom, while the binding between the planar fragment and the aromatic Ge9 ligands is provided by six 2c-2e Pd-Ge σ-bonds and two delocalized 4c-2e σ-bonds. The synthesized cluster represents a rare example of a sandwich compound with the heteroatomic metal planar fragment and inorganic aromatic capping ligands.

In this work, the largest heterometallic supertetrahedral clusters, [Zn6Ge16]4− and [Cd6Ge16]4−, were directly self-assembled through highly-charged [Ge4]4− units and transition metal cations, in which 3-center–2-electron σ bonding in Ge2Zn or Ge2Cd triangles plays a vital role in the stabilization of the whole structure. The cluster structures have an open framework with a large central cavity of diameter 4.6 A for Zn and 5.0 A for Cd, respectively. Time-dependent HRESI-MS spectra show that the larger clusters grow from smaller components with a single [Ge4]4− and ZnMes2 units. Calculations performed at the DFT level indicate a very large HOMO–LUMO energy gap in [M6Ge16]4− (2.22 eV), suggesting high kinetic stability that may offer opportunities in materials science. These observations offer a new strategy for the assembly of heterometallic clusters with high symmetry. © 2020 Wiley-VCH GmbH

Due to the unstable nature of isolated transition metals under real reaction condition, a systematic understanding on how much influence the isolated structure of the active site and the cofed chemicals have on fine tuning the selectivity toward specific reaction pathways is still lacking. Here, we show a combination of kinetic, thermodynamic, and in situ spectroscopy measurements to probe the rWGS and methanation of carbon dioxide on a CeO2-dispersed isolated Ru catalyst (Ru-SnOx/CeO2, structure confirmed by HAADF-STEM) derived from the [Ru@Sn9]6– Zintl cluster decoration. Kinetic measurements, in combination with isotopie-labeling reactions, prove that rWGS and methanation occur through the kinetically relevant C–O bond rupture of surface carboxyl (HOCO*) and surface formate (HCOO*) respectively. A site-selective reaction model has been established on the basis of the response of rWGS and methanation to water pressure. Probably, the rWGS was carried out at the interface between the transition-metal nanoparticles and the support and could be influenced greatly by water, while the methanation was carried out at a site far away from the interface and has a weak dependence on water. This system can be easily extended to some other hydrogenation reactions, thus attracting attention to building isolated structures with Zintl clusters.

The polypnictide complexes of rare earth cations have drawn the attention of the scientific community for their uncommon bonding modes and potential applications. Herein, we present a systematic and comprehensive summary on recent advances in the field of rare earth polypnictides, focusing on their synthesis, structures, and reactivities. The structural stabilizing effects imposed by the electropositive rare earth cations as well as the reducing capability of rare earth precursors in the synthesis of these polypnictide complexes are described in this review. We also disscuss in detail the bonding interactions and coordination modes between rare earth cations and polypnictide clusters as well as the similarities and the peculiarity of some structures.

The chemical bonding of Zintl clusters is still an evolving and hot topic in modern chemistry. In this paper we synthesized a novel [K([2.2.2]crypt)]4 [In8 Bi13 ] complex in a condensed phase. The quantum chemical calculations and X-ray data revealed that the compound consists of the 1:1 mixture of [Bi@In8 Bi12 ]3- and [Bi@In8 Bi12 ]5- clusters. To the date, those clusters are the largest binary clusters composed of In and Bi elements. Herein, we introduce a spherical aromatic description of chemical bonding for such clusters. We show through AdNDP, ELF, and induced magnetic field and quantitative NICS analyzes that both clusters are spherically aromatic which explains their high symmetry, stability, and peculiar magnetic properties. We believe that this work will help researchers in the further development and understanding of chemical bonding in Zintl clusters.

In this work, we report a dimeric cluster anion, {[CuGe9Mes]2}4−, which was isolated as the [K(2,2,2-crypt)]+ salt and characterized by using single-crystal X-ray diffraction and ESI mass spectroscopy. The title cluster represents the first locally σ-antiaromatic compound in the solid state, as well as the first heteroatomic antiaromatic compound.

A heterogeneous cobalt-phosphonate network catalyst, [Co2(2,2′-bipy)(H4L)(H2O)]H2O (Co318), was synthesized by a hydrothermal reaction. The combination of Bronsted acid (–PO3H2) and Lewis acid (Co2+) sites makes Co318 an efficient catalyst for the conversion of saccharides to HMF. Under optimized conditions, glucose was quantitatively consumed and the yield of HMF was as high as 92%. Co318 was recycled four times without the loss of catalytic activity. When microcrystalline cellulose and regenerated cellulose were used, the yields of HMF were 33% and 50%, respectively, at 10 wt% catalyst loading. The yield of HMF increased to 59% when the loading of Co318 was increased to 40 wt%. GC-MS analysis confirmed that the reaction mixture contained both glucose and fructose intermediates, proving that the conversion of cellulose to HMF involved three steps: hydrolysis of cellulose to glucose, isomerization of glucose to fructose, and dehydration of fructose to HMF.

Understanding the structural changes taking place during the assembly of single atoms leading to the formation of atomic clusters and bulk materials remains challenging. The isolation and theoretical characterization of medium-sized clusters can shed light on the processes that occur during the transition to a solid-state structure. In this work, we synthesize and isolate a continuous 24-atom cluster Ge244−, which is characterized by X-ray diffraction analysis and Energy-dispersive X-ray spectroscopy, showing an elongated structural characteristic. Theoretical analysis reveals that electron delocalization plays a vital role in the formation and stabilization of the prolate cluster. In contrast with carbon atoms, 4 s orbitals of Ge-atoms do not easily hybridize with 4p orbitals and s-type lone-pairs can be localized with high occupancy. Thus, there are not enough electrons to form a stable symmetrical fullerene-like structure such as C24 fullerene. Three aromatic units with two [Ge9] and one [Ge6] species, connected by classical 2c-2e Ge-Ge σ-bonds, are aligned together forming three independent shielding cones and eventually causing a collapse of the global symmetry of the Ge244− cluster.

Density functional theory (DFT) calculations were employed to study the stabilities, electronic structures, and vibrational and bonding properties of dianionic pentacarbonyls [TM(CO)

Heterometallic clusters have attracted broad interests in the synthetic chemistry due to their various coordination modes and potential applications in heterogeneous catalysis. Here we report the synthesis, experimental, and theoretical characterizations of four ternary clusters ([M2(CO)6Sn2Sb5]3− (M = Cr, Mo), and [(MSn2Sb5)2]4−, (M = Cu, Ag)) in the process of capturing the hypho- [Sn2Sb5]3− in ethylenediamine (en) solution. We show that the coordination of the binary anion to transition-metal ions or fragments provides additional stabilization due to the formation of locally σ-aromatic units, producing a spherical aromatic shielding region in the cages. While in the case of [Mo2(CO)6Sn2Sb5]3− stabilization arises from locally σ-aromatic three-centre and five-centre two-electron bonds, aromatic islands in [(AgSn2Sb5)2]4− and [(CuSn2Sb5)2]4− render them globally antiaromatic. This work describes the coordination chemistry of the versatile building block [Sn2Sb5]3−, thus providing conceptual advances in the field of metal-metal bonding in clusters.