Charged molecular alloys: synthesis and characterization of the binary anions Pd(7)As(16)(4-) and Pd(2)As(14)(4-)

[Bi10{RuPPh3}3]-: Paramagnetic 13-Vertex Polybismuthide Heteroanion

Ru(PPh3)3Cl2 reacts with Binn- from an ethylenediamine (en) solution of K5Bi4 to yield a new architype of 13-vertex [Bi10{RuPPh3}3]- (1) composed of unprecedented incomplete cuboidal Bi73- and triangular Bi33- held together by {RuPPh3}2+.

Dimeric polybismuth heteroanion of [Rh@Bi10(RhCO)5]2- constructed using Bi10-bowl and square pyramidal Rh@(Rh-CO)5

Redox reaction of the monovalent Rh2(CO)4Cl2 and Binn- (n = 2, 3) from K5Bi4 in ethylenediamine (en) solution produced the decabismuthide-hexarhodium dianion [Rh@Bi10(RhCO)5]2- (1a) wherein a novel Bi10-bowl was constructed from oxidized 2Bi3/2Bi2 open triangles/dimers, which was stabilized by strong bonding to a reduced Rh@(RhCO)5 square pyramid. Two 1a dianons are held together by weak interactions (van der Waals forces and spatial resistance) to form a dimer [Rh@Bi10(RhCO)5]24- (1). The structure and bonding of the novel polybismuthide heteroanion 1 are discussed.

Synthesis and Characterization of [Fe3 (As3 )3 (As4 )]3- , a Binary Fe/As Zintl Cluster With an Fe3 Core

We report here the synthesis and structural characterization of the first binary iron arsenide cluster anion, [Fe₃ (As₃ )₃ (As₄ )]^3- , present in both [K([2.2.2]crypt)]₃ [Fe₃ (As₃ )₃ (As₄ )] (1) and [K(18-crown-6)]₃ [Fe₃ (As₃ )₃ (As₄ )]⋅en (2). The cluster contains an Fe₃ triangle with three short Fe-Fe bond lengths (2.494(1) Å, 2.459(1) Å and 2.668(2) Å for 1, 2.471(1) Å, 2.473(1) Å and 2.660(1) Å for 2), bridged by a 2-butene-like As₄ unit. An analysis of the electronic structure using DFT reveals a triplet ground state with direct Fe-Fe bonds stabilizing the Fe₃ core.

Synthesis and Characterization of Ternary Clusters Containing the [As16]10- Anion, [MM'As16]4- (M = Nb or Ta; M' = Cu or Ag)

The [Nb@As₈]^3- anion was first isolated from solution in 1986, and a number of isostructural [M@Pn₈]^n- clusters (M = Nb, Cr, or Mo; Pn = As or Sb; n = 2 or 3) have since been reported. We show here how anions of this class can be used as synthetic precursors that, in combination with sources of low-valent late transition metals (Cu and Ag), generate ternary polyarsenide cluster anions with unprecedented structural motifs. Chain type [MM'As₁₆]^4- (M = Nb or Ta; M' = Cu or Ag) units are found in compounds 2-5. These clusters contain a nortricyclane-like As₇ cage and a [M@As₈] crown, linked by a single As atom, and represent a fusion of two quite distinct branches of polyarsenide chemistry. Our analysis of the electronic structure confirms that the cluster retains many of the features of the component units. Electrospray ionization mass spectrometry reveals a series of smaller component ions containing 8-12 As atoms, the density functional theory-computed structures of which can be understood in terms of the pseudoelement concept. This work not only presents a new type of coordination mode for As clusters but also offers a point of entry for the rational design of multinary arsenic-based materials.

Synthesis and characterisation of the ternary intermetalloid clusters {M@[As8(ZnMes)4]}3– (M = Nb, Ta) from binary [M@As8]3– precursors

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@As₈]³⁻ (M = Nb, Ta) can be used as synthetic precursors which, when combined with ZnMes₂, generate ternary intermetalloid clusters with 12-vertex cages, {M@[As₈(ZnMes)₄]}³⁻ (M = Nb, Ta). Structural studies are complemented by mass spectrometry and an analysis of the electronic structure using DFT. The synthesis of these clusters presents new opportunities for the construction of As-based nanomaterials.

Two ternary intermetalloid clusters were constructed through binary intermetalloid clusters with a low valent group 12 metal salt. These clusters represent the first example of the structural transformation for intermetalloid clusters.

Zintl Lewis Superacids: Al(Ge9L3)3 (L = H, CH3, CHO, CN)

In quest of a Zintl ion-based Lewis superacids, Al(Ge₉L₃)₃ {L= H, CH₃, CHO and CN} compounds have been designed and their properties have been studied within the framework of conceptual density functional theory-based reactivity descriptors. Superacid property has been identified for these complexes as per the fluoride ion affinity (FIA) values. Studies reveal that Al[Ge₉(CN)₃]₃ and Al[Ge₉(CH₃)₃]₃ behave like superacids as their FIA exceeds the value of SbF₅, which is considered as the strongest Lewis acid. It has been observed that the ligand plays an important role in reactivity as well as in Lewis acidic property.

[Bi7M3(CO)3]2− (M = Co, Rh): a new architype of 10-vertex deltahedral hybrids by the unprecedented polycyclic η5-coordination addition of Bi73− and trimetallic fragments

A new prototype of 10-vertex deltahedral clusters, [Bi₇M₃(CO)₃]²⁻ (M = Co, 1a; M = Rh, 2a), have been synthesized and characterized, resulting from the unprecedented polycyclic η⁵-coordination addition of a Bi₇³⁻ cage and trimetallic fragments.

Chemical Bonding and σ-Aromaticity in Charged Molecular Alloys: [Pd2As14]4- and [Au2Sb14]4- Clusters

We report a computational study on the structures and bonding of a charged molecular alloy D_2h [Pd₂As₁₄]⁴⁻ (1), as well as a model D_2h [Au₂Sb₁₄]⁴⁻ (2) cluster. Our effort makes use of an array of quantum chemistry tools: canonical molecular orbital analysis, adaptive natural density partitioning, natural bond orbital analysis, orbital composition analysis, and nucleus independent chemical shift calculations. Both clusters consist of two X₇ (X = As, Sb) cages, which are interconnected via a M₂ (M = Pd, Au) dumbbell, featuring two distorted square-planar MX₄ units. Excluding the Pd/As or Au/Sb lone-pairs, clusters 1 and 2 are 50- and 44-electron systems, respectively, of which 32 electrons are for two-center two-electron (2c-2e) As-As or Sb-Sb σ bonds and an additional 16 electrons in 1 for 2c-2e Pd-As σ bonds. No covalent Pd-Pd or Au-Au bond is present in the systems. Cluster 1 is shown to possess two globally delocalized σ electrons, whereas 2 has two σ sextets (each associated with an AuSb₄ fragment). Thus, 1 and 2 conform to the (4n + 2) Hückel rule, for n = 0 and 1, respectively, rendering them σ-aromaticity.

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.

{[CuSn5 Sb3 ](2-) }2 : A Dimer of Inhomogeneous Superatoms

Reaction of the binary Zintl anion (Sn2 Sb2 )(2-) with the β-diketiminato complex [LCu(NCMe)] (L=nacnac=[(N(C6 H3 (i) Pr2 -2,6)C(Me))2 CH](-) ) in ethylenediamine or DMF affords the ternary cluster dimer {[CuSn5 Sb3 ](2-) }2 (1) as its [K(crypt-222)](+) salt. The chemical formulation of 1 is supported by energy-dispersive X-ray spectroscopy (EDX) and quantum chemical calculations. Each monomeric part of the dimer represents a trimetallic "[CuSn5 Sb3 ](2-) " cluster, with an architecture in between a tricapped trigonal prism and a capped square antiprism. As shown by quantum chemical investigations, the presence of Sb atoms and, in particular, of Cu atoms in the cluster skeleton makes the monomeric unit behave like an inhomogeneous superatom, which clearly prefers to dimerize, thereby producing a relatively short, yet virtually non-bonding Cu⋅⋅⋅Cu distance.

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.

Understanding of multimetallic cluster growth

The elucidation of formation mechanisms is mandatory for understanding and planning of synthetic routes. For (bio-)organic and organometallic compounds, this has long been realized even for very complicated molecules, whereas the formation of ligand-free inorganic molecules has widely remained a black box to date. This is due to poor structural relationships between reactants and products and the lack of structurally related intermediates—due to the comparably high coordination flexibility of involved atoms. Here we report on investigations of the stepwise formation of multimetallic clusters, based on a series of crystal structures and complementary quantum-chemical studies of (Ge₂As₂)²⁻, (Ge₇As₂)²⁻, [Ta@Ge₆As₄]³⁻, [Ta@Ge₈As₄]³⁻ and [Ta@Ge₈As₆]³⁻. The study makes use of efficient quantum-chemical tools, enabling the first detailed screening of the energy hypersurface along the formation of ligand-free inorganic species for a semi-quantitative picture. The results can be generalized for an entire family of multimetallic clusters.

Elucidation of formation mechanisms of inorganic cluster compounds is challenging due to the high coordination flexibility of the atoms involved. Here, the authors combine crystallographic and quantum-chemical studies to probe the energy hypersurface of a series of multimetallic clusters.

[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.

Controlling band gap energies in cluster-assembled ionic solids through internal electric fields

Assembling ionic solids where clusters are arranged in different architectures is a promising strategy for developing band gap-engineered nanomaterials. We synthesized a series of cluster-assembled ionic solids composed of [As(7)-Au(2)-As(7)](4-) in zero-, one-, and two-dimensional architectures. Higher connectivity is expected to decrease the band gap energy through band broadening. However, optical measurements indicate that the band gap energy increases from 1.69 to 1.98 eV when moving from zero- to two-dimensional assemblies. This increase is a result of the local electric fields generated by the adjacent counterions, which preferentially stabilize the occupied cluster electronic states.

Heteroatomic Deltahedral Clusters: Synthesis and Structures of closo-[Bi3Ni4(CO)6]3-, closo-[Bi4Ni4(CO)6]2-, the Open Cluster [Bi3Ni6(CO)9]3-, and the Intermetalloid closo-[Nix@{Bi6Ni6(CO)8}]4-

Reactions of ethylenediamine solutions of K4Bi5 with Ni(PPh3)2(CO)2 yielded four novel hetero-atomic Bi/Ni deltahedral clusters. Three of them, the 7-atom pentagonal bipyramidal [Bi3Ni4(CO)6]3-, the 8-atom dodecahedral [Bi4Ni4(CO)6]2-, and the Ni-centered or empty 12-atom icosahedral [Nix@[Bi6Ni6(CO)8]4-, are closo-species according to both electron count and shape. The centered icosahedral cluster resembles packing in intermetallic compounds and belongs to the emerging class of intermetalloid clusters. The shape of the fourth cluster, [Bi3Ni6(CO)9]3-, can be derived from the icosahedral Ni-centered [Ni@[Bi6Ni6(CO)8]4- by removal of three Bi- and one Ni-atoms of two neighboring triangular faces. The clusters were structurally characterized by single-crystal X-ray diffraction in compounds with potassium cations sequestered by 2,2,2-crypt or 18-crown-6 ether. They were also characterized in solution by electrospray mass spectrometry.

[Ni5Sb17]4- Transition-Metal Zintl Ion Complex: Crossing the Zintl Border in Molecular Intermetalloid Clusters

K3Sb7 and Ni(COD)2 react in the presence of 2,2,2-cryptand in ethylenediamine solutions ( approximately 1:8 Ni/Sb molar ratio) to give dark-brown crystals of the paramagnetic cluster anion [Ni5Sb17]4- as the [K(2,2,2-crypt)]+ salt. The cluster has a Ni(cyclo-Ni4Sb4) ring unit that sits inside a Sb13 bowl. The structure is similar to that of the previously reported [Pd7As16]4- ion containing a Pd(cyclo-Pd4As4) ring unit that sits inside a Pd2As12 bowl. Density functional theory and bond valence analyses suggest delocalized charge distributions and intermetallic-like properties.

Ligand-Free Deltahedral Clusters of Silicon in Solution: Synthesis, Structure, and Electrochemistry of Si92-

Deltahedral nine-atom clusters of silicon, Si(9)(2-), were synthesized by mild oxidation of a liquid ammonia solution of K(12)Si(17) with Ph(3)GeCl in the presence of 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) or 2,2,2-crypt (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane). The clusters were structurally characterized in [K(18-crown-6)](2)Si(9).C(5)H(5)N (yellow; orthorhombic, Pnma; a = 14.013(1), b = 18.108 (1), c = 18.320 (1) A; Z = 4) crystallized from a pyridine solution of the product of the aforementioned reaction in liquid ammonia. Si(9)(2-) is the first unequivocally characterized nine-atom cluster of group 14 with a charge of 2-. In addition to pyridine, the product from the reaction in liquid ammonia is also soluble in DMF, and the Si(9)(2-) clusters were characterized by mass spectrometry in such a solution. The more reduced clusters Si(9)(3-) have also been crystallized from pyridine solution. Cyclic voltammetry in both pyridine and DMF solutions clearly shows the Si(9)(2-)/Si(9)(3-) redox couple as one-electron reversible process. The structural similarities and differences between Si(9)(3-) and Si(9)(2-) are discussed herein.

Gas Phase, Solution, and Solid State Alkali Ion Binding by the [NbE8]3- (E = As, Sb) Complexes: Synthesis, Structure, and Spectroscopy

Toluene solutions of Nb(toluene)(2) react with ethylenediamine solutions of K(3)E(7) (E = As, Sb) in the presence of 2,2,2-crypt to give [NbAs(8)](3-) (2) and [NbSb(8)](3-) (3) ions, respectively, in low yields. The (133)Cs NMR spectroscopy, ESIMS results (negative ion mode), and single-crystal X-ray structures of the ions are reported. The complexes have S(8)-like E(8) rings with Nb atoms in the center. The 1:1 complex of 2 with Cs+ was observed in solution and also in the gas phase as the oxidized ion [CsNbAs(8)](1-). The anion 2 selectively binds to Cs(+) in solution even in the presence of excess Na(+). Other gas-phase ions formed include [Cs(2)(NbAs(8))](1-), [KCs(NbAs(8))](1-), [KCs(NbAs(8))(2)](1-), [KNbAs(8)](1-), and [K(2)NbAs(8)](1-).

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

The [As@Ni12@As20]3- ion was prepared from As7(3-) and Ni(COD)2 in ethylenediamine solutions and isolated as the Bu4P+ salt (As, arsenic; Ni, nickel; COD, cyclooctadiene; Bu, butyl; P, phosphorus). The anion contains an icosahedral [Ni12(mu12-As)]3- fragment that resides at the center of an As20 dodecahedral (fullerene) cage to give an onion-skin-like [As@Ni12@As20]3- cluster with Ih point symmetry. The icosahedron and pentagonal dodecahedron are reciprocal platonic solids, and the 32 surface atoms form a dimpled geodesic sphere composed of 60 triangular faces. In the gas phase, the [As@Ni12@As20]3- ion sequentially loses all 21 As atoms to form a series of Ni12As(21-x) clusters where 0 </= x </= 21, inclusively.