Interpenetrating As20 fullerene and Ni12 icosahedra in the onion-skin [As@Ni12@As20]3- ion

The cyclo-Sb6 ring in the [Sb6(RuCp*)2]2− ion

The [Sb₆(RuCp*)₂]²⁻ anion represents the first example of a Zintl cluster with a boat-like cyclo-Sb₆ subunit and the first ruthenium polyantimonide complex. The anion is dynamic in solution and fragments in the gas phase. Structural parameters and DFT calculations suggest the possibility of SbSb double bond character.

Assembly of silver Trigons into a buckyball-like Ag180 nanocage

Buckminsterfullerene (C60) represents a perfect combination of geometry and molecular structural chemistry. It has inspired many creative ideas for building fullerene-like nanopolyhedra. These include other fullerenes, virus capsids, polyhedra based on DNA, and synthetic polynuclear metal clusters and cages. Indeed, the regular organization of large numbers of metal atoms into one highly complex structure remains one of the foremost challenges in supramolecular chemistry. Here we describe the design, synthesis, and characterization of a Ag180 nanocage with 180 Ag atoms as 4-valent vertices (V), 360 edges (E), and 182 faces (F)--sixty 3-gons, ninety 4-gons, twelve 5-gons, and twenty 6-gons--in agreement with Euler's rule V - E + F = 2. If each 3-gon (or silver Trigon) were replaced with a carbon atom linked by edges along the 4-gons, the result would be like C60, topologically a truncated icosahedron, an Archimedean solid with icosahedral (Ih) point-group symmetry. If C60 can be described mathematically as a curling up of a 6.6.6 Platonic tiling, the Ag180 cage can be described as a curling up of a 3.4.6.4 Archimedean tiling. High-resolution electrospray ionization mass spectrometry reveals that {Ag3}n subunits coexist with the Ag180 species in the assembly system before the final crystallization of Ag180, suggesting that the silver Trigon is the smallest building block in assembly of the final cage. Thus, we assign the underlying growth mechanism of Ag180 to the Silver-Trigon Assembly Road (STAR), an assembly path that might be further employed to fabricate larger, elegant silver cages.

Between Localization and Delocalization: Ru(cod)2+ Units in the Zintl Clusters [Bi9 {Ru(cod)}2 ]3- and [Tl2 Bi6 {Ru(cod)}]2

Reactions of [K(crypt-222)]₂ (TlBi₃ )⋅0.5 en (1 b) with [Ru(cod)(H₂ CC(Me)CH₂ )₂ ] (A) in 1,2-diaminoethane (en) led to the formation of two compounds with new bismuth-rich cluster anions, [K(crypt-222)]₃ [Bi₉ {Ru(cod)}₂ ]⋅1.5 en (2) and [K(crypt-222)]₂ [Tl₂ Bi₆ {Ru(cod)}]⋅2 tol (3), alongside the salt of a binary nido cluster, [K(crypt-222)]₃ (Tl₄ Bi₅ )⋅2 en (4). The anions in 2 and 3 are two further examples of rare heterometallic clusters containing Ru atoms. As one cod ligand is retained on each Ru atom in both clusters, the anions may be viewed as intermediates on the way towards larger, ligand-free intermetalloid clusters. Quantum-chemical studies provided insight into the bonding situation in these clusters. According to these studies, the anion of 2 features both electron-precise and electron-deficient parts. Electrospray ionization mass spectrometry analysis indicated that the clusters undergo stepwise fragmentation.

Arsenic-Rich Polyarsenides Stabilized by Cp*Fe Fragments

The redox chemistry of [Cp*Fe(η⁵ -As₅ )] (1, Cp*=η⁵ -C₅ Me₅ ) has been investigated by cyclic voltammetry, revealing a redox behavior similar to that of its lighter congener [Cp*Fe(η⁵ -P₅ )]. However, the subsequent chemical reduction of 1 by KH led to the formation of a mixture of novel As_n scaffolds with n up to 18 that are stabilized only by [Cp*Fe] fragments. These include the arsenic-poor triple-decker complex [K(dme)₂ ][{Cp*Fe(μ,η^2:2 -As₂ )}₂ ] (2) and the arsenic-rich complexes [K(dme)₃ ]₂ [(Cp*Fe)₂ (μ,η^4:4 -As₁₀ )] (3), [K(dme)₂ ]₂ [(Cp*Fe)₂ (μ,η^2:2:2:2 -As₁₄ )] (4), and [K(dme)₃ ]₂ [(Cp*Fe)₄ (μ₄ ,η^{4:3:3:2:2:1:1} -As₁₈ )] (5). Compound 4 and the polyarsenide complex 5 are the largest anionic As_n ligand complexes reported thus far. Complexes 2-5 were characterized by single-crystal X-ray diffraction, ¹ H NMR spectroscopy, EPR spectroscopy (2), and mass spectrometry. Furthermore, DFT calculations showed that the intermediate [Cp*Fe(η⁵ -As₅ )]^- , which is presumably formed first, undergoes fast dimerization to the dianion [(Cp*Fe)₂ (μ,η^4:4 -As₁₀ )]^2- .

B40 cluster stability, reactivity, and its planar structural precursor

We report a comprehensive first-principles study of the structural and chemical properties of the recently discovered B₄₀ cage. It is found to be highly reactive and can exothermically dimerize, regardless of the orientation, by overcoming a small energy barrier ≃0.06 eV. The energy gap of the system varies widely with the aggregation of the increasing number of B₄₀ cages, from 3.14 eV in a single B₄₀, to 1.54 eV in the dimer, to 1.25 eV in the trimer. We also explore a recipe for protecting the B₄₀ cage by sheathing it within a carbon shell and identify carbon nanotubes with a radius of ∼6 Å as optimal hosts for an isolated cage. It is demonstrated that B₄₀ can be unfolded into a planar 'molecule' that tessellates the plane. The corresponding 2D boron sheet constitutes a structural precursor foldable into this unique boron cage structure of current interest.

Sb@Ni12@Sb20-/+ and Sb@Pd12@Sb20n Cluster Anions, Where n = +1, -1, -3, -4: Multi-Oxidation-State Clusters of Interpenetrating Platonic Solids

K₅Sb₄ and K₃Sb₇ Zintl ion precursors react with Pd(PPh₃)₄ in ethylenediamine/toluene/PBu₄⁺ solutions to give crystals of Sb@Pd₁₂@Sb₂₀^n-/PBu₄⁺ salts, where n = 3, 4. The clusters are structurally identical in the two charge states, with nearly perfect I_h point symmetry, and can be viewed as an Sb@Pd₁₂ icosahedron centered inside of an Sb₂₀ dodecahedron. The metric parameters suggest very weak Sb-Sb and Pd-Pd interactions with strong radial Sb-Pd bonds between the Sb₂₀ and Pd₁₂ shells. All-electron DFT analysis shows the 3- ion to be diamagnetic with I_h symmetry and a 1.33 eV HOMO-LUMO gap, whereas the 4- ion undergoes a Jahn-Teller distortion to an S = 1/2 D_3d structure with a small 0.1 eV gap. The distortion is predicted to be small and is not discernible by crystallography. Laser desorption-ionization time-of-flight mass spectrometry (LDI-TOF MS) studies of the crystalline samples show intense parent Sb@Pd₁₂@Sb₂₀^- ions (negative ion mode) and Sb@Pd₁₂@Sb₂₀⁺ (positive ion mode) along with series of Sb@Pd_12-y@Sb_20-x^-/+ ions. Ni(cyclooctadiene)₂ reacts with K₃Sb₇ in en/tol/Bu₄PBr solvent mixtures to give black precipitates of Sb@Ni₁₂@Sb₂₀^n- salts that give similar Sb@Ni₁₂@Sb₂₀^-/+ parent ions and Sb@Ni_12-y@Sb_20-x^-/+ degradation series in the respective LDI-TOF MS studies. The solid-state and gas-phase studies of the icosahedral Sb@M₁₂@Sb₂₀^n-/n+ ions show that the clusters can exist in the -4, -3, -1, +1 (M = Pd) and +1, -1 (M = Ni) oxidation states. These multiple-charge-state clusters are reminiscent of redox-active fullerenes (e.g., C₆₀ⁿ, where n = +1, 0, -1, -2, -3, -4, -5, -6).

Transport properties of a three-shell icosahedral matryoshka cluster: a first-principles study

The molecular junction based on three-shell icosahedral matryoshka cluster with huge magnetic moment exhibits robust spin-filtering effect, which highlights it for promising applications in molecular devices.

Counterion-induced crystallization of intermetalloid Matryoshka clusters [Sb@Pd12@Sb20]3−,4−

Two intermetalloid Matryoshka cluster anions [Sb@Pd₁₂@Sb₂₀]^3−,4− were isolated as [K(2,2,2-cryptand)]⁺ and [K(18-crown-6)]⁺ salt, respectively, revealing a feasible route toward controlled isolation of intermetalloid clusters and their potential in electron reservoir materials.

Formation of the intermetalloid cluster [AgSn18]7− – the reactivity of coinage metal NHC compounds towards [Sn9]4−

A series of novel polyanionic coinage metal NHC Zintl clusters [NHC^DippM(η⁴-Sn₉)]³⁻ are obtained from the reaction of [Sn₉]⁴⁻ with NHC^DippMCl (M: Cu, Ag, Au; Dipp: diisopropylphenyl) in liquid ammonia. For M = Ag a larger intermetalloid Ag-bridged nonastannide dimer [(η⁴-Sn₉)Ag(η¹-Sn₉)]⁷⁻ forms.

First-principle investigation on growth patterns and properties of cobalt-doped lithium nanoclusters

A systematic theoretical investigation on cobalt lithium clusters LinCo [1-12] was performed with a DFT approach. The location of global minima and structural evolution were carried out using the partical swarm optimization method. Li6Co is the transition structure in going from low-coordinated structures to three-dimensional torispherical structures with a cobalt atom enclosed by lithium atoms. Maxima of ∆2 E and E b for LinCo were found at n = 3, 6, 8, 10, indicating that these clusters possess higher relative stability than their neighbors. In comparison with small clusters, n = 1-6, the greater electron transfer from Li-2s to Co-3d within cage-like clusters LinCo (n = 7-12) strengthens the bonding effect between Lin and Co, which is reflected in the Wiberg bond index of Co and atomic binding energy analysis. AdNDP analysis verified the presence of both Lewis bonding elements (1c-2e objects) and delocalized bonding elements (6c-2e, 9c-2e and 10c-2e bonds). It is hoped that this theoretical work will provide favorable information to help understand the influence of dopant transition metal atoms on the properties of lithium-based materials.

Heptaphosphide cluster anions bearing group 14 element amide functionalities

Reactions of the protonated heptaphosphide dianion, [HP7](2-), with one equivalent of E[N(SiMe3)2]2 (E = Ge, Sn, Pb) give rise to novel derivatized cluster anions [P7EN(SiMe3)2](2-) (E = Ge (1), Sn (2) and Pb (3)). All three species were characterized by multi-element solution-phase NMR spectroscopy and electrospray ionization mass spectrometry. In addition, 1 and 2 were structurally authenticated by means of single crystal X-ray diffraction in [K(18-crown-6)]2[P7EN(SiMe3)2]·2py. Interestingly, while 2 appears to be indefinitely stable in solution for prolonged periods of time, the germanium-containing analogue, 1, readily decomposes at room temperature giving rise to the dimeric species [(P7Ge)2N(SiMe3)2](3-) (4) and [K(18-crown-6)][N(SiMe3)2]. A low quality single crystal X-ray structure of the former allowed for the confirmation of its composition and connectivity which is consistent with the (31)P NMR spectrum obtained for the anion.

A niobium-necked cluster [As3Nb(As3Sn3)]3− with aromatic Sn32−

A new Zintl cluster [As₃Nb(As₃Sn₃)]³⁻ was synthesized and characterized, in which an As₃ triangle and a bowl-type As₃Sn₃ ligand are bridged by a niobium atom. The Sn₃ ring is found to have σ-aromaticity featured by a delocalized Sn–Sn–Sn σ orbital.

Adding a new dimension to the chemistry of phosphorus and arsenic

We predict two novel highly stable free-standing 2D monolayers of P and As alloyed with Cu (Cu₂X) that have exotic hypercoordination motifs. These are the first predicted hexacoordinate P and planar hexacoordinate As extended alloy sheets.

Interpenetration of a 3D Icosahedral M@Ni12 (M=Al, Ga) Framework with Porphyrin-Reminiscent Boron Layers in MNi9 B8

Two ternary borides MNi9 B8 (M=Al, Ga) were synthesized by thermal treatment of mixtures of the elements. Single-crystal X-ray diffraction data reveal AlNi9 B8 and GaNi9 B8 crystallizing in a new type of structure within the space group Cmcm and the lattice parameters a=7.0896(3) Å, b=8.1181(3) Å, c=10.6497(4) Å and a=7.0897(5) Å, b=8.1579(4) Å, c=10.6648(7) Å, respectively. The boron atoms build up two-dimensional layers, which consist of puckered [B16 ] rings with two tailing B atoms, whereas the M atoms reside in distorted vertices-condensed [Ni12 ] icosahedra, which form a three-dimensional framework interpenetrated by boron porphyrin-reminiscent layers. An unusual local arrangement resembling a giant metallo-porphyrin entity is formed by the [B16 ] rings, which, due to their large annular size of approximately 8 Å, chelate four of the twelve icosahedral Ni atoms. An analysis of the chemical bonding by means of the electron localizability approach reveals strong covalent B-B interactions and weak Ni-Ni interactions. Multi-center dative B-Ni interaction occurs between the Al-Ni framework and the boron layers. In agreement with the chemical bonding analysis and band structure calculations, AlNi9 B8 is a Pauli-paramagnetic metal.

Giant Spherical Cluster with I-C140 Fullerene Topology

We report on an effective cluster expansion of CuBr-linked aggregates by the increase of the steric bulk of the Cp(R) ligand in the pentatopic molecules [Cp(R)Fe(η(5)-P5)]. Using [Cp(BIG)Fe(η(5)-P5)] (Cp(BIG)=C5(4-nBuC6H4)5), the novel multishell aggregate [{Cp(BIG)Fe(η(5:2:1:1:1:1:1)-P5)}12(CuBr)92] is obtained. It shows topological analogy to the theoretically predicted I-C140 fullerene molecule. The spherical cluster was comprehensively characterized by various methods in solution and in the solid state.

[TM13@Bi20]− clusters in three-shell icosahedral matryoshka structure: being as superatoms

Using the density functional theory (DFT) method, three-shell icosahedral matryoshka [TM₁₃@Bi₂₀]⁻ clusters (TM = 3d, 4d) have been systematically examined to explore the possibility of clusters being as superatoms.

Peeling the onion: a revised model of the electron count for matryoshka clusters

A model for understanding two isoelectronic matryoshka clusters based on a layer-by-layer electron count assignment is presented.

Synthesis of arsenic-rich As n ligand complexes from yellow arsenic

The reaction of [{η⁵-Cp'''Co}₂{μ,η^4:4-toluene}] with yellow arsenic yields the arsenic-rich As _n ligand complexes [{Cp'''Co(μ,η^2:2-As₂)}₂] (1), [(Cp'''Co)₄(μ₄,η^4:4:2:2:1:1-As₁₀)] (2) and [(Cp'''Co)₃(μ₃,η^4:4:2:1-As₁₂)] (3), which were comprehensively characterized. The molecular structure of 1 show a triple-decker complex with two As₂ units forming the middle-deck; compound 2 contains an all-arsenic As₁₀ analogue of dihydrofulvalene in the molecular structure. The As₁₂ ligand in 3 represents the largest As _n ligand complex reported so far.

Design of three-shell icosahedral matryoshka clusters A@B₁₂@A2₂₀ (A = Sn, Pb; B = Mg, Zn, Cd, Mn)

We propose a series of icosahedral matryoshka clusters of A@B12@A20 (A = Sn, Pb; B = Mg, Zn, Cd), which possess large HOMO-LUMO gaps (1.29 to 1.54 eV) and low formation energies (0.06 to 0.21 eV/atom). A global minimum search using a genetic algorithm and density functional theory calculations confirms that such onion-like three-shell structures are the ground states for these A21B12 binary clusters. All of these icosahedral matryoshka clusters, including two previously found ones, i.e., [As@Ni12@As20](3-) and [Sn@Cu12@Sn20](12-), follow the 108-electron rule, which originates from the high Ih symmetry and consequently the splitting of superatom orbitals of high angular momentum. More interestingly, two magnetic matryoshka clusters, i.e., Sn@Mn12@Sn20 and Pb@Mn12@Pb20, are designed, which combine a large magnetic moment of 28 µB, a moderate HOMO-LUMO gap, and weak inter-cluster interaction energy, making them ideal building blocks in novel magnetic materials and devices.

Laser ablation synthesis of new gold arsenides using nano-gold and arsenic as precursors. Laser desorption ionisation time-of-flight mass spectrometry and spectrophotometry

RATIONALE

Currently, a limited number of gold arsenides have been described, some of which have important industrial applications, Laser ablation synthesis (LAS) has been employed in an attempt to generate some novel gold arsenide compounds.

METHODS

LAS of gold arsenides was performed using nano-gold (NG) and arsenic as precursors. The clusters formed during laser desorption ionisation (LDI) were analysed by mass spectrometry using a quadrupole ion trap and reflectron time-of-flight analyser to determine the stoichiometry. UV/VIS spectrophotometry was used to follow possible hydrothermal synthesis of gold arsenides.

RESULTS

LAS of NG yielded singly charged gold clusters Aum (+(-)) (m = 1-35). LAS of bulk arsenic and nano-arsenic produced Asn (+(-)) clusters with n = 2-10 and n = 2-20, respectively. Laser ablation of Au-As nano-composites or NG-As mixtures generated Aum (+(-)) (m = 1-12), Asn (+(-)) (n = 3-4), and several series of Aum Asn (+(-)) (m = 1-60, n = 1-18) clusters. Over 450 species of gold arsenide clusters and 212 mixed chlorinated Aum Asn Clx clusters were detected and their stoichiometry determined.

CONCLUSIONS

Many new gold arsenides were synthesised via LAS for the first time with Au-As composites and NG-As mixtures of different Au:As ratios using mass spectrometry to determine cluster stoichiometry. The resolved stoichiometry of Aum Asn clusters determined in this study could accelerate the development of advanced Au-As nano-materials.

Making practical use of the pseudo-element concept: an efficient way to ternary intermetalloid clusters by an isoelectronic Pb(-)-Bi combination

Syntheses of [K([2.2.2]crypt)](+) salts of binary Pb-Bi Zintl anions and their reaction with ZnPh(2) or Ni(cod)(2), yielding ternary intermetalloid Ni-Pb-Bi or Zn-Pb-Bi clusters, proved the use of binary precursors with fully isoelectronic atoms as an efficient and thus valuable synthetic approach to this class of clusters. (207)Pb NMR and ESI mass spectra provided insight into the solution behavior of the binary or ternary cages.

Heterotrimetallic compounds containing Mo-M-Li [M = K, Rb and Cs] clusters: synthesis, structure, bonding, aromaticity and theoretical investigations of Li2M2 [M = K and Rb] and Cs4 rings

A new polydentate fac-trioxo molybdenum complex, [MoO(3)L](3-) {LH(3) = nitrilotriacetic acid}, has been synthesized by the reaction of lithium molybdate with iminodiacetic acid. The trinegative complex anion coordinates the alkali metal cations, K(+), Rb(+) or Cs(+). The potassium, rubidium and cesium complexes, [Li{K(H(2)O)(2)}MoO(3)L](n) (1), [Li{Rb(H(2)O)(2)}MoO(3)L](n) (2) and [Cs{Li(H(2)O)}(2)MoO(3)L](n) (3), form heterotrimetallic coordination chains, containing planar rings of Li(2)M(2) (M = K or Rb) and Cs(4). Theoretical investigations on these rings were carried out using NICS calculations and ab initio ring current maps, revealing aromaticity to be of limited significance.

[Co(η5-P5){η2-P2H(mes)}]2-: a phospha-organometallic complex obtained by the transition-metal-mediated activation of the heptaphosphide trianion

A carbon copy: The chemical activation of the heptaphosphide trianion with [Co(PEt(2)Ph)(2)(mes)(2)] (see picture; 1) yields the novel phospha-organometallic complex [Co(η(5)-P(5)){η(2)-P(2)H(mes)}](2-) (2). The reaction product maintains the nuclearity of the parent cluster, but extensive cage fragmentation takes place to yield a diamagnetic "inorganometallic" cobalt complex.