Au2PbP2, Au2TlP2, and Au2HgP2: Ternary Gold Polyphosphides with Lead, Thallium, and Mercury in the Oxidation State Zero

The polyphosphide Au₂PbP₂ was prepared by reaction of the elemental components using liquid lead as a reaction medium. Well-developed crystals were obtained after dissolving the matrix in hydrochloric acid. Their crystal structure was determined from four-circle X-ray diffractometer data: Cmcm, a=323.6(1) pm, b=1137.1(2) pm, c=1121.8(1) pm, Z=4, R=0.023 for 478 structure factors and 20 variable parameters. The structure contains zigzag chains of phosphorus atoms with a typical single-bond distance of 219.4(2) pm. The two different kinds of gold atoms are both in linear phosphorus coordination with typical single-bond distances of 232.6(2) and 234.2(2) pm, and the lead atoms have only metal neighbors (7 Au and 2 Pb). Accordingly, chemical bonding of the compound may be expressed by the formula (Au⁺¹)₂Pb^±0(P⁻¹)₂. The corresponding thallium and mercury polyphosphides Au₂TlP₂ (a=324.1(1) pm, b=1136.1(1) pm, c=1122.1(1) pm) and Au₂HgP₂ (a=322.1(1) pm, b=1131.4(2) pm, c=1122.6(1) pm) were found to be almost isotypic with Au₂PbP₂. Their crystal structures were refined from single-crystal X-ray data to R=0.036 (682 F values, 25 variables) and R=0.026 (539 F values, 35 variables), respectively. The structure of these compounds may also be described as consisting of a three-dimensional network of condensed 8- and 10-membered Au₂P₆ and Au₄P₆ rings forming parallel channels, which are filled by the lead, thallium, and mercury atoms. The lead atoms are well localized in these channels, while the thallium and even more the mercury atoms occupy additional positions within these channels. Freshly prepared samples of Au₂HgP₂ show reproducibly slightly different axial ratios and larger cell volumes (ΔV=0.5%) than those after exposure of the samples to air for several days.     

从头计算方法比较研究B2Au4, Al2Au4和BAlAu4的几何和电子结构

Au/H 相似性的研究是现代化学中的一个热门话题. 我们从理论上报道Au/H 相似的新成员: 共价化合物B₂Au₄, 离子化合物Al₂Au₄和BAlAu₄. 采用密度泛函和波函数理论方法对比研究了缺电子体系B₂Au₄、Al₂Au₄和BAlAu₄的几何和电子结构. 详细讨论了它们基态结构的轨道、适应性自然密度划分(AdNDP)和电子局域函数(ELF)分析. 计算结果表明稍微扭曲变形的C₂B₂Au₄是基态结构, 在这个共价化合物中含有两个B―Au―B三中心二电子(3c-2e)键. 然而C_3v Al⁺(AlAu₄)^-和C_3v Al⁺(BAu₄)^-被研究证明是含有三个X―Au―Al 三中心二电子键的类盐化合物(在Al₂Au₄中X=Al, BAlAu₄中X=B). Al₂Au₄和BAlAu₄是至今为止首例报道的在离子缺电子体系中含有金桥键的化合物. 同时计算了B₂Au₄^-、Al₂Au₄^- 和BAlAu₄^- 阴离子基态结构的绝热剥离能和垂直剥离能, 为实验表征提供依据. 文中报道的金桥键为共价键和离子键相结合的缺电子体系提供了一个有趣的键合模式, 有助于设计含有高度分散金原子的新材料和催化剂.     

Synthesis and molecular structure of [Au3Ru4(μ3-H)(CO)12(PPh3)3]

The title compound can be prepared in good yield by heating either [Ru₄(μ-H)₄(CO)₁₂] or [Au₂Ru₄(μ₃-H)₂(CO)₁₂(PPh₃)₂] with [AuMe(PPh₃)] in toluene. The related compound [Au₃Ru₄(μ₃-H)(μ-dppm)(CO)₁₂(PPh₃)] has also been prepared. Both trigoldtetraruthenium clusters undergo dynamic behaviour in solution, involving intramolecular rearrangement of the metal core, as revealed by variable temperature NMR studies. The crystal structure of [Au₃Ru₄(μ₃-H)(CO)₁₂(PPh₃)₃] has been established by an X-ray diffraction study. The metal atom core comprises a trigonal bipyramidal AuRu₄ unit with two AuRu₂ faces capped by gold atoms.     

Au10(TBBT)10: the Begining and the End of Aun(TBBT)m Nanoclusters

Gold(I) thiolate compounds (i.e. Au^I-SR) are important precursors for the synthesis of atomically precise Au_n(SR)_m nanoclusters. However, the nature of the Au^I-SR precursor remains elusive. Here, we report that the Au₁₀(TBBT)₁₀ complex is a universal precursor for the synthesis of Au_n(TBBT)_m nanoclusters (where TBBT=4-tertbutylbenzenethiol/thiolate). Interestingly, the Au₁₀(TBBT)₁₀ complex is also found to be re-generated through extended etching of the Au_n(SR)_m nanoclusters with excess of TBBT thiol and O₂. The formation of well-defined Au₁₀(TBBT)₁₀ complex, instead of polymeric Au^I-SR, is attributed to the bulkiness of the TBBT thiol. Through 1D and 2D NMR characterization, the structure of Au₁₀(TBBT)₁₀ is correlated with the previously reported X-ray structure, which contains two inter-penetrated Au₅(TBBT)₅ rings. The photophysical property of Au₁₀(TBBT)₁₀ complex is further probed by femtosecond transient absorption spectroscopy. The accessibility of the precise Au₁₀(TBBT)₁₀ precursor improves the efficiency of the synthesis of the Au_n(TBBT)_m nanoclusters and is expected to further facilitate excellent control and understanding of the reaction mechanisms of nanocluster synthesis.     

B2Au20/-/2-: 硼金团簇中的硼-硼多重键

采用密度泛函和波函数理论方法对B₂Au^20/-/2-的几何结构和电子结构进行研究. 计算结果表明阴离子B₂Au^2- ([Au-B B-Au]^-) (C_2h, ²A_u)和B₂Au^22- ([Au-B≡B-Au]^2-) (C_2h, ¹A_g)的基态结构均为线性结构, 即以含有多重键的BB单元(B B或B≡B)为中心, 两端各连接一个Au原子, 但两端的B－Au键不在同一直线上, 结构稍有变形; 而中性分子B₂Au₂ ([Au-B＝B-Au]) (D_∞h, ³Σ_g^-)的基态结构是以B＝B为中心, 两端各与一个Au原子相连的完美的线性结构. C_2h B₂Au^2-的单电子垂直剥离能和对称性伸缩振动频率的计算结果为实验表征提供依据.另外, 计算发现无机盐B₂Au₂Li₂结构中仍包含B≡B, 此结果一方面为其实验合成提供了可能性, 另一方面表明含有B≡B的B₂Au₂^2-结构极为稳定, 可作为结构单元存在于凝聚相中.     

Ca7Au3 and Ca5Au4, two structures closely related to the Th7Fe3 and Pu5Rh4 types

Two new intermetallic compounds have been synthetized and structurally studied by single crystal diffractometric data: Ca₇Au₃ (oP80, space groupPbca,a = 20.742(8), b = 18.036(8), c = 6.665(2) A?,Z = 8, R = 0.051) and Ca₅Au₄ (mP18, space groupP2₁/c, a = 8.028(3), b = 8.019(6), c = 7.727(3) A?, β = 109.16(6)°,Z = 2, R = 0.104). Both atomic arrangements, which represent new structural types, are based on Au-centered Ca trigonal prisms and are geometrically related to the Th₇Fe₃ and Pu₅Rh₄ structures.     

Nanosized Au4Pd32(CO)28(PMe3)14 Containing a Highly Distorted Encapsulated Au4 Tetrahedron: Proposed Multi-Twinned Growth-Pattern from Two Deformed Au-Centered Double Icosahedral-Based Fragments*

As part of an extensive effort to synthesize a variety of nanosized gold–palladium carbonyl phosphine clusters, the neutral Au₄Pd₃₂(CO)₂₈(PMe₃)₁₄ (1) was isolated and unambiguously characterized by low-temperature CCD X-ray diffraction and IR measurements. This nanosized Au₄Pd₃₂ cluster was prepared in low yields (<5%) from the room-temperature reaction of Pd₁₀(CO)₁₂(PMe₃)₆ (2) with Au(SMe₂)Cl in THF/acetone. The heretofore unknown molecular geometry of 1 of pseudo-D₂ (222) symmetry (without methyl substituents) may be viewed to arise from a relatively strong (Au–Au)-bonded linkage (2.64 Å (av)) of two pentagonal-bipyramidal (μ₅-Au)(μ₅-Pd)Pd₅ polyhedra; this generated 14-atom Au₂Pd₁₂ unit may be considered as a markedly deformed part of a 19-atom Au-centered double icosahedron without the inner pentagon (corresponding to five missing inner atoms). In turn, two Au₂Pd₁₂ units form a central composite-twinned Au₄Pd₂₂ kernel via vertex-fusion of two common Pd atoms along with additional formation of four Pd–Pd bonding, four Au–Pd bonding, and two weaker secondary Au–Au bonding interactions at 2.90 Å (av) (versus the other two diagonal Au–Au nonbonding ones at 3.51 Å (av)); this resulting Au₄Pd₂₂P₈ kernel is augmented by the addition of two triangular Pd₃P core-fragments and four exopolyhedral PdP groups to give the Au₄Pd₃₂P₁₄ framework of 1. This cluster is stabilized by 28 bridging COs, of which 20 are doubly bridging and 8 triply bridging. The largest metal-core diameter of 1 along one pseudo C₂ axis is 1.1 nm. This new type of multi-twinned metal cluster has direct relevance to both ligated and non-ligated (naked) non-crystalline metal nanoparticles, many of which possess multiple twinning and/or disorder.^*Dedicated to Professor F. A. Cotton on the occasion of his 75th birthday in recognition of numerous seminal contributions to modern Inorganic Chemistry. Professor Cotton has a truly unparalleled scientific career in Inorganic Chemistry in terms of the overall composite effects of his highly prolific research productivity, his tremendous impact on former graduate students, postdoctoral associates, and collaborators, and his matchless textbooks/monographs.     

Synthesis, Characterization, Luminescence, and Electrochemistry of New Tetranuclear Gold(I) Amidinate Clusters: Au4[PhNC(Ph)NPh]4, Au4[PhNC(CH3)NPh]4, and Au4[ArNC(H)NAr]4

The syntheses and the X-ray structures of the tetranuclear gold(I) benzamidinate, Au₄[PhNC(Ph)NPh]₄, and the tetranuclear gold(I) acetamidinate, Au₄[PhNC(CH₃)NPh]₄, clusters are reported. The clusters are produced by the reaction of the sodium salt of an amidine ligand with the gold precursor Au(THT)Cl in a (1:1) stoichiometry. The average Au...Au distance between adjacent Au(I) atoms is ∼2.9 ?, typical of compounds having an aurophilic interaction. The four gold atoms are arranged in a square (Au...Au...Au... = 88–91°) in the acetamidinate and in a distorted square (Au...Au...Au... = 82–97°) in the benzamidinate derivative. Electrochemical oxidation of the tetranuclear complex Au₄[PhNC(Ph)NPh]₄ show three reversible waves at 0.87, 1.19, 1.42 V vs. Ag/AgCl at a scan rate of 100 mV/s in CH₂Cl₂ similar to the three reversible waves seen before from the tetranuclear complexes Au₄[ArNC(H)NAr]₄, Ar = C₆H₄-4-OMe, Ar = C₆H₄-4-Me, and Ar = C₆H₃-3,5-Cl. A summary of the chemistry of the tetranuclear Au(I) amidinate complexes Au₄[ArNC(H)NAr]₄, Ar = C₆H₄-4-OMe, C₆H₃-3,5-Cl, C₆H₄-4-Me, C₆H₄-3-CF₃, C₆F₅, C₁₀H₇ also is presented. The tetranuclear clusters Au₄[ArNC(H)NAr]₄, Ar = C₆H₄-4-OMe, Ar = C₆H₄-3-CF₃, Ar = C₆H₄-4-Me and Ar = C₆H₄-3,5-Cl are the first tetranuclear gold(I) cluster species from group 11 elements to show fluorescence at room temperature. The lifetimes of the naphthyl and trifluoromethylphenyl complexes are in the millisecond range indicating phosphorescent processes. Recently it has been shown that Au₄[ArNC(H)NAr]₄ are very effective catalysts upon calcination for room temperature CO oxidation. Congratulations to Dieter Fenske, a superb synthetic chemist with exceptional talents in cluster chemistry, on the occasion of his 65th birthday.     

New ab initio Potential Energy Surfaces for Cl（^2P3/2,^2P1/2）＋H2 Reaction

New global three dimensional potential energy surfaces for the Cl＋H2 reactive system have been constructed using accurate multireference configuration interaction calculations with a large basis set. The three lowest adiabatic potential energy surfaces correlating asymptotically with Cl（^2p）＋H2 have been transformed to adiabatic representation, which leads to a fourth coupling potential for non-linear geometries. In addition, the spin-orbit coupling surfaces have also been computed using the Breit-Pauli Hamiltonian. Properties of the new potential are described. Reaction dynamics based on the new potential agrees with the recent experimental results quite well.     

Les antimonites antiferromagnetiques MnSb2O4 et NiSb2O4

Neutron diffraction has been used to study the variation of antiferromagnetic order in the antimony isomorphous MnSb₂O₄ (T_N ～ 60 K) and NiSb₂O₄ (T_N ～ 46 K). The magnetic moments have been related to the Mn²⁺ and Ni²⁺ spins and magnetostrictive effects have been interpreted. The influence of the method of synthesis is mentioned: polycrystalline MnSb₂O₄ has been obtained from hydrothermal synthesis. Orthorhombic distortions are not connected with magnetic interactions but with structural defects.     

The reactions of 2-benzoylpyridine with [RuHCl(CO)(PPh3)3] and [(C6H6)RuCl2]2

The reactions of [RuHCl(CO)(PPh₃)₃] and [(C₆H₆)RuCl₂]₂ with 2-benzoylpyridine have been examined, and two novel ruthenium(II) complexes – [RuCl(CO)(PPh₃)₂(C₅H₄NCOO)] and [RuCl₂(C₁₂H₉NO)₂] – have been obtained. The compounds have been studied by IR and UV–Vis spectroscopy, and X-ray crystallography. The molecular orbital diagrams of the complexes have been calculated with the density functional theory (DFT) method. The spin-allowed singlet–singlet electronic transitions of the compounds have been calculated with the time-dependent DFT method, and the UV–Vis spectra of the compounds have been discussed on this basis.     

Magnetic susceptibilities of UO2ThO2 solid solutions

The magnetic susceptibility of UO₂ThO₂ solid solutions has been measured from room temperature to 2.0 K. The magnetic moment and the Weiss constant have been determined in the temperature range in which the Curie-Weiss law holds. For the solid solutions showing antiferromagnetic transition, the Néel temperature has been also determined. These values decrease monotonically with increasing ThO₂ concentration. The results were analyzed using the molecular field theory which includes the interaction between next-nearest neighbor spins. The interactions between nearest neighbor spins, J₁, and those between next-nearest neighbor spins, J₂, both decrease with increasing ThO₂ concentration. The change of J₁ with composition is larger than that of J₂. The effect of magnetic dilution with ThO₂ is considered to be stronger on the interaction between nearest neighbor uranium ions.     

Magnetic susceptibilities of UO2ZrO2 solid solutions

The magnetic susceptibility of cubic solid solutions of UO₂ and ZrO₂ with a fluorite structure has been measured from room temperature to 2.3 K. The magnetic moment and the Weiss constant have been determined in the temperature range where the Curie-Weiss law holds. These values decrease monotonically with increasing ZrO₂ concentration. The solid solutions of UO₂ diluted with 0 ～ 20 mole% ZrO₂ show an antiferromagnetic transition and have a linear dependence of Néel temperature on concentration, with a critical concentration of 78 mole% UO₂. The molecular field theory which includes next-nearest-neighbor interaction was applied to the results. The interaction between nearest-neighbor spins, J₁, decreases with increasing ZrO₂ concentration, whereas that between next-nearest-neighbor spins, J₂, increases. The behavior of J₁ against composition is thought to be caused from the direct effect of magnetic dilution with ZrO₂. Regarding the behavior of J₂, the effect of increasing magnetic interaction due to the smaller distance of uranium ions is considered to be stronger than the magnetic dilution effect.     

Interfacial electron transfer at TiO2 nanostructured electrodes modified with capped gold nanoparticles: The photoelectrochemistry of water oxidation

We have studied the photoelectrochemical behavior of nanostructured anatase electrodes modified with gold nanoparticles stabilized either with citrate (Au_cit) or with tetraoctylammonium bromide (Au_TOAB). An increase both in photocurrent and in photopotential was observed in 0.05 M NaOH upon modification with Au_TOAB. This behavior is attributed to an efficient hole consumption at the gold nanoparticles, which implies an effective hole transport to them from the TiO₂ nanostructure, probably facilitated by the capping agent. Once in the Au particles, the holes would promote an oxidation process (O₂ generation), which requires that the Au nanoparticles attain a high enough local electrode potential. This is possible as long as the Au_TOAB nanoparticles may behave as nanocapacitors with a very low capacity (ca. 1 aF) and thus the accumulation of a few holes may induce important changes in their potential. In acidic medium or in the presence of 0.1 M CH₃OH no enhancement was detected. In the case of TiO₂ modified with Au_cit, no increase of the photoelectrochemical response was observed in any case. It is suggested that a proper design of the metal/semiconductor nanojunctions may lead to an enhanced charge separation and to the eventual development of photoinduced metal electrocatalysis.     

AB initio molecular orbital studies of CF3O2H,CF3O2F and CF2(OF)2

Ab initio calculations employing an extended 4-31G basis set have been applied to the highly fluorinated molecules, CF₃O₂H, CF₃O₂F and CF₂(OF)₂. Partial geometry optimizations have also been carried out on these molecules allowing a comparison between theory and the recently completed gas-phase electron diffraction results. The O-O bond distance in CF₃O₂ H is found to be longer (by 0.02 Å) than the corresponding bond in CF₃O₂F while the CO bond is found to be shorter (by 0.02 Å) in CF₃O₂H. The OF bond in CF₃O₂F is found to be longer (by 0.03–0.04 Å) than the corresponding bond in CF₃OF or F₂O. Torsional barriers have been computed for CF₃O₂H and CF₃O₂F with the aid of Fourier analysis of the potential curves. CF₃O₂H is found to have a torsional potential about the peroxide bond rather similar to that found for H₂O₂ while in CF₃O₂F the cis and trans barriers are predicted to be much larger (14.6 and 8.4 kcal mol^?1, respectively). The threefold barrier to rotation of the CF₃ group in CF₃O₂F is predicted to be 4.4 kcal mol^?1. Various conformations of CF₂(OF)₂ have also been studied with conformations consistent with the operation of the gauche-effect being most stable. Bond separation energies and molecular properties have also been computed for these molecules.     

Ba3 (VO4)2-K2 Ba(MoO4)2 and Pb3 (VO4)2-K2 Pb(MoO4)2 systems

Phase equilibria in the Ba₃(VO₄)₂-K₂Ba(MoO₄)₂ and Pb3(VO₄)₂-K₂Pb(MoO₄)₂ systems have been investigated. In the first system, a continuous series of substitutional solid solutions with the palmierite structure is formed, and in the second one, the polymorphic transition in lead orthovanadate at 100°C restricts the extent of the palmierite-type solid solution to 10–100 mol % K₂Pb(MoO₄)₂. Original Russian Text ? V.D. Zhuravlev, Yu.A. Velikodnyi, A.S. Vinogradova-Zhabrova, A.P. Tyutyunnik, V.G. Zubkov, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 10, pp. 1746–1748.     

Structural Evolution and Electronic Properties of Au2Gen-/0 (n=1-8) Clusters: Anion Photoelectron Spectroscopy and Theoretical Calculations

Investigating the structures and properties of Au-Ge mixed clusters can give insight into the microscopic mechanisms in gold-catalyzed Ge films and can also provide valuable information for the production of germanium-based functional materials. In this work, size-selected anion photoelectron spectroscopy and theoretical calculations were used to explore the structural evolution and electronic properties of Au₂Ge_n^-/0 (n=1-8) clusters. It is found that the two Au atoms in Au₂Ge_n^-/0 (n=1-8) showed high coordination numbers and weak aurophilic interactions. The global minima of Au₂Ge_n^- anions and Au₂Ge_n neutrals are in spin doublet and singlet states, respectively. Au₂Ge_n^- anions and Au₂Ge_n neutrals showed similar structural features, except for Au₂Ge₄^-/0 and Au₂Ge₅^-/0. The C_2v symmetric V-shaped structure is observed for Au₂Ge₁^-/0, while Au₂Ge₂^-/0 has a C_2v symmetric dibridged structure. Au₂Ge₃^-/0 can be viewed as the two Au atoms attached to different Ge-Ge bonds of Ge₃ triangle. Au₂Ge₄^- has two Au atoms edge-capping Ge₄ tetrahedron, while Au₂Ge₄ neutral adopts a C_2v symmetric double Au atoms face-capping Ge₄ rhombus. Au₂Ge_5-8^-/0 show triangular, tetragonal, and pentagonal prism-based geometries. Au₂Ge₆ adopts a C_2v symmetric tetragonal prism structure and exhibits σ plus π double bonding characters.     

Alkynyl derivatives of gold complexes containing C6H3-5-Me-2-EPh2 (E = P, As) ligands

[Au₂Cl₂{μ-2,2′-Ph₂As(5,5′-Me₂C₆H₃C₆H₃)AsPh₂}] reacts with phenylacetylene or ethynylferrocene to give the corresponding digold(I) bis(alkynyl) derivatives [Au₂(CCR)₂{μ-2,2′-Ph₂As(5,5′-Me₂C₆H₃C₆H₃)AsPh₂}] [R = Ph (4), Fc (5)]. In contrast, products resulting from the reaction with 1,3- or 1,4-diethynylbenzene (deb) depend markedly on the dichlorodigold(I) complex to ligand ratio. When an excess of alkyne is used, the expected bis(alkynyl) complexes [Au₂X₂{μ-2,2′-Ph₂As(5,5′-Me₂C₆H₃C₆H₃)AsPh₂}] [X = 1,3-deb (6), 1,4-deb (7)] are obtained, but when using a 1:1 molar ratio poorly soluble, presumably polymeric, species are formed. Attempts to prepare a digold(II) bis(alkynyl) derivative by treatment of [Au₂Cl₂(μ-C₆H₃-5-Me-2-PPh₂)₂] with ethynylferrocene in the presence of NaOMe gives a mixture of species, the recrystallization of which yielded a crystal of [{2-(FcCC)-4-MeC₆H₃PPh₂}Au(CCFc)] (1). The reaction of [Au₂Cl₂(μ-C₆H₃-5-Me-2-AsPh₂)₂] with phenylacetylene, 1,3- or 1,4-deb gives a mixture of unidentified products.     

Some studies on the solid solutions in the systems Sr2Nb2O7Eu2Nb2O7 and Sr2Ta2O7Eu2Ta2O7

Preparation of new solid solutions containing divalent europium have been tried in the systems Eu₂Nb₂O₇Sr₂Nb₂O₇ and Eu₂Ta₂O₇Sr₂Ta₂O₇. These solid solutions described as Eu_2xSr_2(1?x)M₂O₇ (M = Nb and Ta) exist in a pure orthorhombic phase in a limited region of x from 0 to about 0.5. The compounds with compositions close to Eu₂M₂O₇ exist but techniques have not been found to prepare them in pure form.     

Theoretical Studies on Dehydrogenation Reactions in Mg2(BH4)2(NH2)2 Compounds

Borohydrides have been recently hightlighted as prospective new materials due to their high gravimetric capacities for hydrogen storage. It is, therefore, important to under-stand the underlying dehydrogenation mechanisms for further development of these ma-terials. We present a systematic theoretical investigation on the dehydrogenation mecha-nisms of theMg₂(BH₄)₂(NH₂)₂ compounds. We found that dehydrogenation takes place most likely via the intermolecular process, which is favorable both kinetically and thermo-dynamically in comparison with that of the intramolecular process. The dehydrogenation of Mg₂(BH₄)₂(NH₂)₂ initially takes place via the direct combination of the hydridic H in BH₄^- and the protic H in NH₂^-, followed by the formation of Mg-H and subsequent ionic recombination of Mg-H^δ- …H^δ+N.