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A tetrameric cluster composed entirely of (aryl)Sn units, [DMPSn]4 (DMP=2,6-dimesitylphenyl), has been prepared by reduction of [DMPSnCl]2 with a variety of reductants. This cluster was characterized in solution by multinuclear NMR spectroscopies, as well as in the solid-state by single crystal X-ray diffraction analysis. This species is stereochemically nonrigid in solution and possesses a cyclo-Sn4 core whose DMP substituents are equivalent at higher temperatures. The solid-state molecular structure is remarkably unsymmetrical and possesses a nearly planar cyclo-Sn4 core. The DMP substituents are arranged such that three are approximately coplanar, while one is nearly perpendicular to the cyclo-Sn4 core. Density functional theory calculations for a [PhSn]4 model system show that this distorted geometry about the cyclo-Sn4 core maximizes σ-bonding between the Sn centers in a manner reminiscent of trans-bent bonding in the heavy group 14 analogues of alkenes and alkynes.

The synthetic approach towards molecules that contain Ge atoms with oxidation state 0, and which are exclusively connected to other Ge atoms, is explored by using anionic clusters extracted from binary solids. Besides providing a novel variable method for the introduction of alkenyl moieties to [Ge9 ] cluster compounds, this work expands the spectrum of mixed-functionalized [Ge9 ] cluster anions, which are suitable for the straightforward synthesis of zwitterionic compounds upon coordination to metal cations. In detail, the synthesis of a series of mixed-functionalized [Ge9 ] clusters is reported, including [Ge9 {Si(TMS)3 }3 PRRI ] (R=tBu, RI =(CH2 )3 CH=CH2 ; 2) and [Ge9 {Si(TMS)3 }2 PRRI ]- (R and RI : alkyl, alkenyl, aryl, aminoalkyl; 3 a to 11 a, TMS: (trimethyl)silyl). In 2 and 3 a, pentenyl functionalization of the [Ge9 ] clusters was achieved by reaction of the novel chlorophosphine tBu{(CH2 )3 CH=CH2 }PCl (1) with silylated [Ge9 ] clusters. Furthermore, the reactivity of the cluster anions 3 a to 11 a towards NHCDipp MCl (NHCDipp =1,3-di(2,6-diisopropylphenyl)imidazolylidine; M=Cu, Ag) showed a dependency on the steric demand of the phosphine either zwitterions (3-MNHCDipp to 7-MNHCDipp ) featuring P-M interactions are formed, or Ge-M coordination (8-MNHCDipp to 11-MNHCDipp ) occurs. For M=Ag, the formation of zwitterionic complexes was unequivocally proven by NMR investigations showing 1 J(31 P-107 Ag/109 Ag) spin-spin coupling.

We report the observation of dimerization of two 8-electron superatom cluster units in the crystallographic structures of Au2 Ag42 (SAdm)27 (BPh4 ) and [Au2 Ag48 (S-t Bu)20 (Dppm)6 Br11 ]Br(BPh4 )2 nanoclusters. The crystallographic analysis reveals that both nanoclusters have a Au2 Ag24 core made of two separated icosahedral without sharing metal atoms, and each icosahedron has an eight-electron (8e) closed shell (1S2 1P6 ). The valence electronic structures of these two nanoclusters are analogous to that of a Ne atom dimer (Ne2 ) according to the density functional theory (DFT) analysis. This is the first crystallographic observation of the dimerization of 8-electron superatom units. This study enriches the fundamental knowledge on metal superatom clusters and implies the possibility for further assembling metal superatom building blocks into higher order superatom molecules.

When reacting the organic functionalized tin selenide clusters [(SnR1 )3 Se4 Cl] (A, R1 =CMe2 CH2 C(O)Me) or [(SnR1 )4 Se6 ] (B) with (SiMe3 )2 Se and [Ag(PPh3 )3 Cl] at -78 °C in CH2 Cl2 , a microcrystalline intermediate (compound 1) precipitates, which was investigated by magic angle spinning (MAS) NMR spectroscopy, powder X-ray diffraction (PXRD), energy dispersive X-ray (EDX) spectroscopy, and quantum chemistry calculations, to derive information about its composition and structure. Compound 1 re-dissolves under reorganization into the organo-functionalized Ag/Sn/Se cluster compound [Ag6 (μ6 -Se)(Ag8 Se12 ){(R1 Sn)2 Se2 }6 ] (2), or the mixed-valence cluster [(AgPPh3 )2 (SnII Cl)2 Se2 {(R1 SnIV )2 Se2 }2 ] (3), depending on the presence or the exclusion of daylight, respectively. The addition of N2 H4 ⋅H2 O to a solution of 1 yields selectively [Ag7 (μ7 -Se)(Ag7 Se12 ){(R2 Sn)2 Se2 }6 ] (4, R2 =CMe2 CH2 C(N2 H2 )Me), the Ag/Sn/Se core of which is isomeric to that of 2. 2-4 were characterized by X-ray diffraction. NMR spectroscopic studies on solutions of 1 indicate the co-existence of different species.

Dodecameric (Sn12 ) and hexameric topologies dominate monoalkyltin-oxo cluster chemistry. Their condensation, triggered by radiation exposure, recently produced unprecedented patterning performance in EUV lithography. A new cluster topology was crystallized from industrial n-BuSnOOH, and additional characterization techniques indicate other clusters are present. Single-crystal X-ray analysis reveals a β-Keggin cluster, which is known but less common than other Keggin isomers in polyoxometalate and polyoxocation chemistry. The structure is formulated [NaO4 (BuSn)12 (OH)3 (O)9 (OCH3 )12 (Sn(H2 O)2 )] (β-NaSn13 ). SAXS, NMR, and ESI MS differentiate β-NaSn13 , Sn12 , and other clusters present in crude "n-BuSnOOH" and highlight the role of Na as a template for alkyltin Keggin clusters. Unlike other alkyltin clusters that are cationic, β-NaSn13 is neutral. Consequently, it stands as a unique model system, absent of counterions, to study the transformation of clusters to films and nanopatterns.

Halogen bonds are a subset of noncovalent interactions with rapidly expanding applications in materials and medicinal chemistry. While halogen bonding is well known in organic compounds, it is new in the field of boron cluster chemistry. We have synthesized and crystallized carboranes containing Br atoms in two different positions, namely, bound to C- and B-vertices. The Br atoms bound to the C-vertices have been found to form halogen bonds in the crystal structures. In contrast, Br atoms bound to B-vertices formed hydrogen bonds. Quantum chemical calculations have revealed that halogen bonding in carboranes can be much stronger than in organic architectures. These findings open new possibilities for applications of carboranes, both in materials and medicinal chemistry.

Selective dissolution of hafnium-peroxo-sulfate films in aqueous tetramethylammonium hydroxide enables extreme UV lithographic patterning of sub-10 nm HfO2 structures. Hafnium speciation under these basic conditions (pH>10), however, is unknown, as studies of hafnium aqueous chemistry have been limited to acid. Here, we report synthesis, crystal growth, and structural characterization of the first polynuclear hydroxo hafnium cluster isolated from base, [TMA]6 [Hf6 (μ-O2 )6 (μ-OH)6 (OH)12 ]⋅38 H2 O. The solution behavior of the cluster, including supramolecular assembly via hydrogen bonding is detailed via small-angle X-ray scattering (SAXS) and electrospray ionization mass spectrometry (ESI-MS). The study opens a new chapter in the aqueous chemistry of hafnium, exemplifying the concept of amphoteric clusters and informing a critical process in single-digit-nm lithography.

Metal-organic frameworks (MOFs) based on group 3 and 4 metals are considered as the most promising MOFs for varying practical applications including water adsorption, carbon conversion, and biomedical applications. The relatively strong coordination bonds and versatile coordination modes within these MOFs endow the framework with high chemical stability, diverse structures and topologies, and interesting properties and functions. Herein, the significant progress made on this series of MOFs since 2018 is summarized and an update on the current status and future trends on the structural design of robust MOFs with high connectivity is provided. Cluster chemistry involving Y, lanthanides (Ln, from La to Lu), actinides (An, from Ac to Lr), Ti, and Zr is initially introduced. This is followed by a review of recently developed MOFs based on group 3 and 4 metals with their structures discussed based on the types of inorganic or organic building blocks. The novel properties and arising applications of these MOFs in catalysis, adsorption and separation, delivery, and sensing are highlighted. Overall, this review is expected to provide a timely summary on MOFs based on group 3 and 4 metals, which shall guide the future discovery and development of stable and functional MOFs for practical applications.

A synthetic strategy for functionalization of the three vertices of o-carborane and the attachment of the obtained triped to the solid support was developed. Further functionalization of the triped with short DNA sequences by automated DNA synthesis was achieved. The proposed methodology is a first example of boron cluster chemistry on a solid support opening new perspectives in boron cluster functionalization.

Within the reinvestigation of Ni–Sb carbonyl cluster chemistry, we report here the synthesis and characterization of the new [Ni19Sb4(CO)26]4– cluster and the synthesis, structure, magnetic characterization and electrical resistivity of the viologen salts of the previously known [Ni13Sb2(CO)24]n– (n = 2, 3) anionic species. The crystal structures of [NEt4]4[Ni19Sb4(CO)26], [EtV]8[Ni13Sb2(CO)24]3·4DMF·2C6H14 and [EtV]3[Ni13Sb2(CO)24]·1.5THF (EtV = 1,1′-diethyl-4,4′-bipyridilium cation, DMF = N,N-dimethylformamide, THF = tetrahydrofuran) are described. Notably, the unit cell of [EtV]8[Ni13Sb2(CO)24]3·4DMF·2C6H14 involves a mixture of two [Ni13Sb2(CO)24]3– trianions and one [Ni13Sb2(CO)24]2– dianion, as it also contains eight [EtV]+· radical monocations, which are assembled in infinite stacks. In contrast, the unit cell of the [EtV]3[Ni13Sb2(CO)24]·1.5THF salt contains four [Ni13Sb2(CO)24]3– trianions along with twelve [EtV]+· radical monocations, four of which are arranged into two pairs of isolated dimers, whereas the other two sets of four form two infinite stacks that extend over the whole crystal. The charges of the miscellaneous ions have been assigned on the basis of electroneutrality and spectroscopic evidence. More specifically, the infrared spectra of [EtV]8[Ni13Sb2(CO)24]3·4DMF·2C6H14, both in the solid state and in solution, clearly indicate the presence of a 2:1 mixture of [Ni13Sb2(CO)24]3– and [Ni13Sb2(CO)24]2– anions. Resistivity measurements performed on pellets of powdered samples indicate that the [EtV]8[Ni13Sb2(CO)24]3·4DMF·2C6H14 salt substantially behaves as an insulator. A study of the magnetic behaviour of [EtV]8[Ni13Sb2(CO)24]3·4DMF·2C6H14 evidences pairing among the electrons of the EtV+· molecules, in agreement with DFT calculations, and the odd-electron clusters behave as paramagnetic centres of spin S = 1.

Because of quantum-size effects, molecular gold clusters are promising materials for applications in nanoscience and nanotechnology. Owing to the feasible synthesis of Au11 species out of [Au(PPh3)Cl], this material is the subject of many investigations, although its full crystal structure including the ligand shell remained unknown. We have been able to obtain the solid-state structure at atomic resolution, even for the cocrystallized solvent molecules: The composition of the red crystals corresponds to [Au11(PPh3)7Cl3]·CH2Cl2·1.5{(CH3CH2)2O}. The gold atoms in the cluster subtend a core of almost C3v symmetry derived from a centered icosahedron, which is present in most Au11 species. The mean Au–Au distance amounts to 2.8076 A and the mean Au–Cl distance to 2.3730 A; both are in good agreement with comparable data in structurally characterized gold clusters. The mean core diameter, measured between the centers of the gold atoms of opposite sides of the cluster, is about 4.9 A, and the overall van der Waals diameter can be estimated to 19.8 A. The optical absorbance of [Au11(PPh3)7Cl3] in solution reveals characteristic peaks at 318 and 406 nm and a shoulder between 450 and 550 nm. The peak at 406 nm and the shoulder can also be resolved for the solid. The energy of the first optically active electron transition of ca. 2.0 eV is very close to the theoretically derived data of the HOMO–LUMO gap. In accordance with the literature, only one singlet in the 31P{1H} NMR spectrum is found at δ = 52 ppm, even at –80 °C.

Macropolyhedral boron-containing cluster compounds are those in which single clusters are intimately fused such that the covalent multicentre bonding characteristics typical of the boranes extend through and are part of the intercluster conjunction. Many of the most significant developments in macropolyhedral boron-containing cluster chemistry have occurred since the mid-to-late 1990s. Of these, metal-containing macropolyhedral species are reviewed here, with particular emphasis on syntheses and the novel skeletal structures that result.

Cluster chemistry of intermetallics with valence electron counts (VECs) in the range of 2.0–3.0 is intriguing. Lithiation of polar intermetallics in this VEC region is found to be an effective chemical route to produce new complex structures with different stability mechanisms. In this work, two new complex intermetallic structures have been discovered in the Ca–Li–Zn system: Ca12LixZn59–x and Ca15LixZn75–x. Ca12LixZn59–x, x ≈ 5.65(3)–14.95(3), forms in the trigonal space group R3m, with a = 9.074(1)–9.1699(2) A, c = 53.353(1)–53.602(1) A, and Z = 3. In comparison, Ca15LixZn75–x, x ≈ 19.07(2), crystallizes in the space group P63/mmc, with a ≈ 9.183(1) A, c ≈ 45.191(5) A), and Z = 2. Both structures are members of a large intergrowth family featuring slabs of dimers (D) and trimers (T) stacking along [001], with the sequences DTDDTDDTD for Ca12LixZn59–x and TDDDTDDD for Ca15LixZn75–x. Each dimer consists of two face-sharing Zn-centered hypho-icosahedra, and each trimer comprises a Li-centered icosahedron ...

A family of interwoven molecular inorganic knots, shaped like the ‘Star of David’, was prepared by the employment of naphthalene-2,3-diol in 3d/4f-metal cluster chemistry; the isoskeletal dodecanuclear compounds exhibit slow relaxation of the magnetization and magnetocaloric properties, depending on the metal ion.

ConspectusMetal hydride clusters have historically been studied to unravel their aesthetically pleasing molecular structures and interesting properties, especially toward hydrogen related applications. Central to this work is the hydride ligand, H¯, the smallest closed-shell spherical anion known. Two new developments in polyhydrido nanocluster chemistry include the determination of heretofore unknown hydride coordination modes and novel structural constructs, and conversion from the molecular entities to rhombus-shaped copper nanoparticles (CuNPs). These advances, together with hydrogen evolution and catalysis, have provided both experimentalists and theorists with a rich scientific directive to further explore. The isolation of hexameric [{(Ph3P)CuH}6] (Stryker reagent) could be regarded as the springboard for the recent emergence of polyhydrido copper cluster chemistry due to its utilization in a variety of organic chemical transformations. The stability of clusters of various nuclearity was improved t...

The chemistry of the azido-bridged coordination clusters continues to attract the intense interest of synthetic inorganic chemists and scientists working in the interdisciplinary field of Molecular Magnetism. In this review we have focused on describing aspects of synthesis, structures and magnetic properties of azido-bridged 3d- and d/d′-metal clusters with nuclearities equal to or higher than 4. Some of the clusters display slow magnetic relaxation at very low temperatures, mainly due to the ferromagnetic metal⋯metal exchange interactions propagated through the end-on azido ligand. The chemistry of polynuclear, azido-bridged 3d-metal complexes embedded in lacunary polyoxometalates is also discussed.

Small AgnPd (n = 5) clusters and their hydrides AgnPdH (n = 5) have been studied by density functional theory calculations. For bare clusters, the structures in which the Pd atom has a maximum number of neighboring Ag atoms tend to be energetically favorable. Hydrogen prefers binding to AgPd bridge site of AgnPd clusters except for Ag5Pd. The binding energy has a strong odd–even oscillation. The electron transfers are from Ag atoms to Pd in bare clusters and are from metal clusters to H in cluster hydrides. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

Pyridine/ethylenediamine solutions of [Sn(9)SnCy(3)](3-) (1) react with [Pd(PPh(3))(4)] to give new clusters [Pd@Sn(9)SnCy(3)](3-) (2) and [Pd@Sn(9)PdSnCy(3)](3-) (3), depending on stoichiometry. These compounds are formed sequentially and are the first transition metal derivates of exo-substituted Zintl clusters. Oxidative insertion of a Pd atom into the Pd@Sn(9)-SnCy(3) bond of 2 to form 3 represents a new reaction type for Zintl cluster compounds. The conversion Sn(9)(4-)→1→2→3 is a rare case in which charge and mass are conserved in a series of Zintl clusters. Complexes 1, 2, and 3 are all highly fluxional in solution. In all three clusters, the nine Sn vertices are in rapid exchange on the NMR timescale. In 1 and 2, the exo-SnCy(3) substituent also scrambles intramolecularly around the outside of the clusters. In 3, the SnCy(3) group remains attached to the vertex Pd atom. The disparate reactions with the other RSn(9)(3-) ions are discussed.

The following is a review of the synthesis, chemistry, and catalytic properties of small, well-defined supported metal clusters, Ir4 and Ir6. These supported clusters are synthesized either by adsorption of ligated molecular iridium clusters with tetrahedral and octahedral frameworks, for Ir4 and Ir6, respectively, or by adsorption of single-iridium-atom complexes followed by treatment to form clusters on the supports. The most insightful characterizations of supported metal clusters have been carried out by infrared and X-ray absorption spectroscopies and aberration-corrected scanning transmission electron microscopy. Reactions of the supported clusters include ligand modifications and ligand removal, oxidative fragmentation, and migration leading to metal aggregation. Reactivities and catalytic properties of the clusters (e.g., for olefin hydrogenation) depend on the cluster size and the support (which acts as a ligand) and are distinct from those of supported particles that resemble bulk iridium. Transient spectroscopic data illustrate that the structures of the active species in ethylene hydrogenation catalysis switch reversibly from Ir4 to single-iridium-atom complexes in response to changes in the ethylene/H2 ratio in the gas phase. Density functional theory has been used to predict properties of these clusters, notably their ability to add hydrogen, and the agreement between theory and experiment is good. Recent advances in the characterization of supported Ir4 and Ir6 clusters have been crucial in the elucidation of their behavior, and these methods apply as well to the more complicated structures of industrial supported metal catalysts.

Recently, polynuclear manganese complexes have received much attention owing to their relevance to diverse fields ranging from bioinorganic chemistry to molecular magnetic materials. On the one hand, they can act as biomimetic models for the active center of photosystem II (PSII); on the other hand, they are good candidates for single-molecule magnets (SMMs) or molecular magnetic refrigeration, both generally requiring high spin ground states. Notably, wheel-shaped manganese complexes occupy a special position among polynuclear complexes, not only because of their pleasing structural aesthetics but also for their potential to be the basis for quantum computation as suggested by theoretical studies. Up to now, the study of wheel-shaped manganese complexes has largely focused on ring like manganese clusters that lack the metal center, whose nuclearity includes [Mn6], [Mn8], [Mn10], [Mn12], [Mn16], [Mn20], [Mn22], [Mn24], and [Mn84]. However, most of the ring like polynuclear manganese cluster complexes are antiferromagnetic, so it remains a great challenge to design and synthesize ferromagnetic ring like manganese cluster complexes. In the course of investigations of polynuclear manganese complexes with high spin ground states, we have recently successfully prepared a ferromagnetic disk like MnMn3Na I 3 heptanuclear complex with a spin ground state of 9 using the trianion of 1,1,1-tris-(hydroxymethyl)propane (H3thme) as the ligand, [6b] which prompted us to further construct other types of wheel-shaped manganese complexes utilizing this ligand. By reaction of H3thmp with Mn ACHTUNGTRENNUNG(acac)2 in the presence of (R-, S-, or racemic) 2-aminopropane-1,2-diol in MeCN solution, we have obtained a novel ring like octadecanuclear mixed-valence manganese cluster complex, [Mn8Mn III 6Mn IV 4(OH)4O2ACHTUNGTRENNUNG(acac)6ACHTUNGTRENNUNG(thmp)12]· 5H2O 1 (Hacac=acetylacetone), which shows an overall ferromagnetic property and possesses a spin ground state of 20, the largest value for the ring-shape manganese cluster complexes so far. Herein we report its synthesis, crystal structure, and magnetic properties. Brechin et al. have recently successfully utilized the reaction of H3thmp or 2-(bromomethyl)-2-(hydroxymethyl)-1,3propanediol with the Mn metal triangle [Mn3O ACHTUNGTRENNUNG(O2CCH3)6 ACHTUNGTRENNUNG(HIm)3]ACHTUNGTRENNUNG(O2CCH3) (HIm= imidazole) in CH3OH to yield several ring like manganese cluster complexes with nuclearities of [Mn16] and [Mn22], f] where the acetate and MeO anions take part in the bridging roles, along with the thmp anion (and oxo anion). We chose Mn ACHTUNGTRENNUNG(acac)2 as the manganese source in MeCN to yield 1, so only the thmp anion, the oxo anion, and hydroxyl anion were observed to bridge Mn atoms in 1. To the best of our knowledge, 1 is the first carboxylate-free ring like polynuclear manganese cluster complex constructed from a poly(hydroxymethyl) ligand rather than a salicylhydrazide derivative ligand. Although 2aminopropane-1,2-diol is not incorporated into the structure of 1, it obviously plays an important role in the formation of 1, because no crystalline products could be obtained when the reaction was carried out in the absence of (R-, S-, or racemic) 2-aminopropane-1,2-diol. Nevertheless, it is hard to exactly determine the inducing role of 2-aminopropane-1,2diol and the real reaction pathways as is the case with all polynuclear manganese cluster chemistry. Complex 1 crystallizes in the monoclinic space group C2/ c. As shown in Figure 1, the structure of 1 consists of nine manganese atoms in the asymmetric unit that, along with the other nine symmetry related manganese atoms, are arranged in a ring-shaped topology. The manganese oxidation states were established by bond-valence sum (BVS) calculations and charge-balance considerations. The octadecanuclear core of 1 contains eighteen defect [Mn3O4] cuboidal units that are face-shared (Figure 2a). The O atoms of the [Mn3O4] units are from two m3-O 2 anions, four m4-OH anions, and twelve thmp ligands, acting as the corners of the partial cubes. Each of the two m3-O 2 anions connects [a] Dr. C.-M. Liu, Prof. D.-Q. Zhang, Prof. D.-B. Zhu Beijing National Laboratory for Molecular Sciences Center for Molecular Sciences/Institution of Chemistry Chinese Academy of Sciences Fax: (+86)010-62569349 E-mail : cmliu@iccas.ac.cn Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/asia.201000511.

This part of the review on metal cluster compounds deals with clusters containing isolated main group element atoms, with high nuclearity clusters and metal cluster fluxionality. It will be obvious that main group element atoms strongly influences the geometry, stability and reactivity of the clusters. High nuclearity clusters are of interest in there own due to the diversity of the structures adopted, but their intermediate position between molecules and the metallic state makes them a fascinating research object too. These both sites of the metal cluster chemistry as well as the frequently observed ligand and core fluxionality are related to the cluster metal and surface analogy.

The interest in transition metal cluster catalysis has developed tremendously over the past decade because of the potential benefits metal cluster compounds may provide over traditional catalysts. Although these expectations have not been met yet transition metal cluster catalysis has offered many insights into the phenomenon of catalysis and still remains the most important driving force of the metal cluster chemistry. This part of the review on transition metal cluster compounds deals with the homogeneous and heterogeneous catalysis by such compounds.

Two new copper-thiacalix[4]arene compounds, [Cu-2(1)-Cl-2(H(4)TC4A)](CH3OH) (1) and [Cu(I)2Cl(2)(H(4)PTC4A)](CH3OH)(CHCl3)(0.5) (2) (where H(4)TC4A = p-tert-butylthiacalix[4]arene and H(4)PTC4A = p-phenylthiacalix[4]arene), were synthesized by the solvothermal method in the mixed CH3OH/CHCl3 (1: 1) solvent and reassembled in air at room temperature to two other structures, [(Cu4Cl3)-Cl-II(HCO2)(TC4A)(CH3-OH)(2)(H2O)](CHCl3)(CH3OH)(2.7) (3) and [(Cu4Cl4)-Cl-II(PTC4A)(CH3OH)(4)] (4), respectively. All these four compounds were characterized by TG analyses, FTIR spectroscopy, and singlecrystal X-ray diffraction analyses. Compounds 1 and 2 feature two-dimensional layered networks, while compounds 3 and 4 are assembled by some tetranuclear units.

In the coordination, hypervalent and cluster chemistry, three important characteristic properties are the maximum coordination number, magic number, and core coordination number. Yet, few studies have considered these three numbers at the same time for an ML(n) cluster with n larger than 8. In this article, we systematically studied the three properties of SiLi(n) (n = 4-16) clusters at the B3LYP/6-31G(d), B3LYP/6-311++G(2d), and CCSD(T)/6-311++G(3df)//B3LYP/6-311++G(2d) (for energy only) levels. Various isomeric forms with different symmetries were calculated. For each SiLi(n) (n = 4-9), silicon cohesive energy (cE) from SiLi(n) --Si + Li(n) reaction, vertical ionization potential (vIP), and vertical electron affinity (vEA) were obtained for the lowest-energy isomer. We found that the maximum Li-coordination number of Si is 9, which is the largest number among the known MLi(n) clusters. All cE, vIP, and vEA values predicted that 6 is the magic Li-coordination number of Si. For small SiLi(n) (nor = 6) clusters, Li atoms favor direct coordination to Si, whereas for larger SiLi(n) (nor = 7) clusters, there is a core cluster that is surrounded by excessive Li atoms. The core Li-coordination number is 6 for SiLi(n) (n = 7,8), 7 for SiLi(n) (n = 9,10), 8 for SiLi(n) (n = 11-15) and 9 for SiLi(n) (nor = 16). Through the calculations, we verified the relationship between the structure and stability of SiLi(n) with the maximum coordination number, magic number, and core coordination number.

The initial use of 2-pyridyl-substituted oximes [(py)C(R)-NOH R = Me, Ph]/sulfate blend in nickel(II) chemistry has yielded a family of hexanuclear clusters. The syntheses, structures and magnetic properties are reported of [Ni6(SO4)4-(OH){(py)C(Me)NO} 3{(py)C(Me)NOH}3(MeOH)2(H2O)] (1), [Ni6(SO4)4(OH){(py)C(ph)NO}3{(py) C(ph)NOH}3(MeOH)3] (2) and [Ni6(SO 4)4(OH){(py)C(ph)NO}3{(py)C(ph)NOH} 3(H2O)3] (3), where (py)C(Me)NOH is methyl 2-pyridyl ketone oxime and (py)C(ph)NOH is phenyl 2-pyridyl ketone oxime. The hexanuclear molecules present in the three complexes have similar structures which contain the [Ni6(μ3-OH)(μ3-SO 4)3(μ3-ONR)3]2+ core. The core consists of six NiII ions arranged as two parallel equilateral triangular subunits, one small (Ni⋯Ni ca. 3.3 Å) and the other larger (Ni⋯Ni ca. 6.0 Å). Characteristic IR bands are discussed in terms of the known structures of 1-3. The magnetic properties of 1 and 2 have been studied by variable-temperature dc magnetic susceptibility techniques which indicate antiferromagnetic interactions. A simple 2-J model was found to be adequate to describe the similar thermal variation of the molar magnetic susceptibilities of 1 and 2. © Wiley-VCH Verlag GmbH & Co. KGaA, 2007. 18 2761 2774 Cited By :50

The cluster chemistry with functionalised trimethylsilyl reagents was investigated. The oxidation of the one-dimensional coordination polymer 1/∞[{Ag2(PhS2P−PS2Ph)dppe}·dppe]∞ leads to the formation of [Ag12(PhS2P−PS2Ph)6(dppeS)6] (dppeS = Ph2P(CH2)2P(S)Ph2]. The dianionic ligand [PhPS2−PS2Ph]2− could possibly give rise to a new class of macrocyclic transition-metal chalcogenides. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Transition metal cluster chalcogenides with cubane-type structures are relevant to our understanding of several industrial and biological catalytic processes. Recent advances in cluster chemistry owe much to the development of rational synthetic approaches, an aspect that is emphasised in this review which focuses on cuboidal clusters of molybdenum and tungsten (M) with M2M′2S4 and M3M′Q4 (Q = S, Se) central units that incorporate a first-row transition metal atom (M′). Special attention has been paid to the non-aqueous chemistry of these compounds. The structural features of these complexes are discussed in relation to their electronic structures within the framework of molecular orbital theory, spectroscopic, magnetic and electrochemical experimental data. Finally, the importance of these clusters in catalysis, nonlinear optics and in the formation of supramolecular adducts is discussed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Chance discovery is ubiquitous in the history of science, especially in areas where theory has tended to lag behind experimental findings. In fields such as organometallic and boron cluster chemistry, serendipity has been particularly important in opening new directions and shaping the evolution of these fields. In this article selected examples from the author's half century of research in borane, carborane, and metallaborane chemistry are used to illustrate the often intricate interplay between unexpected findings and targeted synthesis.

Density functional theory is used to investigate the assembling of metallic clusters to yield stable or metastable cluster solids. Motivated by the observed high stability of the Al13H cluster, which has a substantial highest occupied and lowest unoccupied molecular orbitals (HOMO–LUMO) gap, we have modeled the assembling of those clusters. For a favorable relative orientation of each cluster with respect to all its neighbors, a cluster solid is predicted and its structure appears to be stable at least up to 150 K, which is the highest temperature in our simulations. We have also studied the chemical bonding in the stoichiometric solid alloys PbA, where A is one of the alkali elements Na, K, Rb, or Cs. Those crystals exist in an ordered phase formed by tetrahedral Pb4 clusters surrounded by the alkali atoms. The study of this family of natural cluster compounds reveals the coating role played by the cations, providing further insight into the favorable conditions required for the formation of cluster solids. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001

Cluster chemistry in the third main group has long been restricted to compounds of the lightest element boron. However, about 30 years ago the first compounds were synthesized and characterized in which single aluminium atoms adopted positions of high connectivity in polyhedral borane or carbaborane clusters. The next successful step in these efforts to establish a chemistry analogous to that of the polyboranes with the heavier elements of the third main-group was the synthesis of closo-dodecaaluminate [Al12iBu12]2– at the beginning of the nineties, which was the first homonuclear aluminium analogue of a polyborate anion and had a core exclusively formed by aluminium atoms. Another class of interesting new aluminium compounds was formed by the carbaalanes, which were synthesized and characterized for the first time only recently. They have clusters of aluminium and carbon atoms, and are similar to the carbaborane analogues in that their structures seem to be determined by the number of electron pairs in their molecular centers in accordance with the Wade rules.

Reaction between three equivalents of the silaborate [NEt4][MeSiB10H12] (2) and one equivalent of [Ru3(CO)12] resulted in almost quantitative formation of the mononuclear transition metal complex [NEt4][Ru(CO)3(η5-MeSiB10H10)] (5), which was characterized by X-ray structure analysis. The trinuclear ruthenium complex [NEt4][Ru3(CO)8(η5-MeSiB10H10)] (7) was synthesized in high yield from the reaction of one equivalent of 2 and [Ru3(CO)12]. The cluster 7 reacts with two equivalents of PMe2Ph with substitution of two carbonyl groups to give the substitution product [NEt4][Ru3(CO)6(PMe2Ph)2(η5-MeSiB10H10)] (8).

Layers of niobium clusters that are linked to each other through zigzag chains of edge-sharing [TiCl4 O2 ] ocatahedra are the central structural features of the title compound. Bridging of the chains by [(Nb6 Cl8i O4i )Cl6a ]6- clusters results in the formation of empty tunnels (a section of the structure is shown on the right).

The importance of 3d/4f-metal cluster chemistry is outlined, and the employment of 2-pyridyl ketone- and 2-pyridyl oxime-based ligands for the preparation of low-nuclearity Ni II /Ln III complexes (Ln = lanthanide) is reviewed. The synthetic utility of the "metal com- plexes as ligands" and "one-pot" approaches is critically discussed. The small nuclearity of the products permits the in-depth analysis of their magnetic properties.

The new compounds Ca6Pt8Cd16 (I), SrPt2Cd4 (II), and BaPt2Cd4 (III) are identified in the title systems.

Recent work on gas phase distribution, reactivity, and catalysis of neutral metal, metal oxide/carbide/sulfide clusters, investigated by single photon ionization coupled with time-of-flight mass spectrometry, is reviewed. Oxidation–reduction and bond activation reactions catalyzed by neutral metal and metal compound clusters are investigated, in order to understand the catalytic process at a molecular level, and reveal possible full catalytic cycles for related condensed phase reactivity and processes. Density functional theory calculations for these systems enable exploration of the geometric and electronic structures of clusters and determination of reaction intermediates and transition states, as well as reaction mechanisms, by comparing the results of theoretical calculations and experimental observations. Reactivity of metal oxide clusters with small gas phase molecules (CO, SO2, and hydrocarbons), which is associated with the oxygen-rich or -deficient nature of the cluster, is discussed in terms of bond enthalpy, cluster spin state, and unpaired spin density of the clusters. For bond activation catalytic reactions on metal and metal compound clusters, we describe how adsorption of reactant molecules on active metal sites of clusters, association energy between reactant molecules and clusters, and activation energy (barriers) on the reaction potential energy surface can be constructed and compared to generate a reaction mechanism. Experimental and theoretical studies shown in this review also provide unique insights into how the application of gas phase neutral metal cluster chemistry is instructive in the understanding of important fundamental aspects of practical catalysis in the condensed phase.

Hydrogen-atom transfer (HAT), as one of the fundamental reactions in chemistry, is investigated with state-of-the-art gas-phase experiments in conjunction with computational studies. The focus of this Minireview concerns the role that the intrinsic properties of gaseous oxo-clusters play to permit HAT reactivity from saturated hydrocarbons at ambient conditions. In addition, mechanistic implications are discussed which pertain to heterogeneous catalysis. From these combined experimental/computational studies, the crucial role of unpaired spin density at the abstracting atom becomes clear, in distinct contrast to recent conclusions derived from solution-phase experiments.

Transition metal complexes in which hydrocarbons serve as σ,σ-, σ,π- or π,π-bound bridging ligands are currently of great interest. This review presents efficient and directed syntheses for such compounds, which often have very aesthetic structures. These reactions are among the most important reaction types in modern organometallic chemistry. They can be a useful aid for the synthesis of tailor-made compounds, for example, for models of catalytic processes and, specifically, for the construction of heterometallic compounds. We will discuss reactions of electrophilic complexes with nucleophilic ones, numerous transformations of (functionalized) hydrocarbons with metal complexes, the currently very topical complexes with bridging acetylide and carbide ligands, and organometallic polymers, which can be expected to have interesting and novel materials properties. Chisholm1 has described the importance of these complexes as follows: “Central to the development of polynuclear and cluster chemistry are bridging ligands and central to organometallic chemistry are metal–carbon bonds. Thus bridging ligands hold a pivotal role ins the development of Binuclear and polynuclear organometallic chemistry”.

[Htmnd][S2B16H17] (tmnd: N,N,N′,N′-tetramethylnaphthalene-1,8-diamine) is synthesized from a mixture of [S2B17H17], [RhCl2(η5-C5Me5)] 2, and tmnd dissolved in dichloromethane (25 °C, 24 h, 9% yield).

The reaction between closo-1,2-C 2 B 8 H 10 and NH 2 Bu t resulted in a straightforward cluster expansion to give the 11-vertex azadicarbaborane anti-11-Bu t -arachno-5,10,11-C 2 N B 8 H 12 , characterized by NMR and mass spectroscopy, together with the accompanying syn isomer.

Monoclonal antibodies (Mabs) and their immunoreactive fragments continue to be attractive, but as yet unproven, vehicles for the selective delivery of therapeutic quantities of 1oB to tumors for the purpose of boron neutron capture therapy (BNO. Available chemical methodologies and boron-containing reagents for immunoprotein conjugation will be delineated along with the use of designed, precisely synthesized macromolecules which serve as "1OB-trailer" reagents for protein conjugation. The latter designed species have been investigated and are either synthetic peptide-like oligomers containing large quantities of boron in their component a-amino acids or they are hydrophilic polyamides comprised of boron-rich repeating units. Both classes of reagent are produced throu h solid-supported syntheses (Memfield methodology). Use of these precisely synthesizedq0B-trailer species as conjugation reagents equipped with analytically useful fluorescent labels may provide the 103 B-atoms per Mab molecule required for effective BNCT. This methodology provides Mab conjugation with a minimal loss of structural information while providing chemical reproducibility. The in vivo evaluation of this approach has led to the identification of potential improvements in the use of immunoproteins as vehicles for the selective delivery of boron (or other agents) to tumor cells. Consequently, the synthesis of a hydrophilic and boron-rich peptide which is structurally discrete and immunodirected is in progress.

The reactivity of many "naked" clusters and the means by which these may be isolated as stable "chemical" clusters are briefly considered for the orbitally-rich transition metals, where clusters must be sequestered by coordination with ligands, and for the heavier main group elements that utilize only t hree p orbitals in bonding. shell configurations a re known for the latter group both as solids at room temperature and in cluster beams. at elevated temperatures are o btained with chloride, sulfide, etc. as ligands. Greater versatility and variety have recently been found for electron-precise clusters that require an interstitial atom Z within M6X12-type clusters for stability, as with the Ai(Zr6(Z)XI2)X, family and rare-earth-eleme nt analogs where 22 different examples of Z and many structure types are known for X = C1, Br, I. A newer and even broader area of cluster chemistry involves interstitials bonded within chains of confacial octahedra in a variety of polar intermetallic phases that occur in the Mn5Si3 structure (-&(Mn3Si3-Mn2)), where the l arge differences in valence state energies of the component atoms generally assure that valence bonding levels on the main-group element are filled first. The electron-rich Zr5Sb3 host is found to form Zr5Sb3Z phases with at least 16 examples of Z. calculational results for the binary host and for the sulfide are considered. Examples of similar investigations are described for the Zr5Sn3, Zr5Pb3, La5Ge3, La5Pb3, and M&, M = Ca, Sr or Ba and 6 = Sb or Bi.