Gas Phase Ion Chemistry of Transition Metal Clusters: Production, Reactivity, and Catalysis

This review focuses on the use of mass spectrometry to examine the gas phase ion chemistry of metal clusters. Ways of forming gas phase clusters are briefly overviewed and then the gas phase chemistry of silver clusters is discussed to illustrate the concepts of magic numbers and how reactivity can be size dependent. The chemistry of other bare and ligated metal clusters is examined, including mixed metal dimer ions as models for microalloys. Metal clusters that catalyze gas phase chemical reactions such as the oxidation of CO and organic substrates are reviewed. Finally the interface between nanotechnology and mass spectrometry is also considered.     

CDMPC手性固定相对金属簇化合物的手性拆分

应用纤维素三(3,5-二甲基苯基氨基甲酸酯)(CDMPC)手性固定相对2种羰基钌金属簇合物进行了拆分,通过流动相组成、流速和样品溶剂等条件对拆分影响的考察对拆分条件进行了优化。实验结果表明,簇合物1和簇合物2分别在含乙醇(V(hexane):V(ethanol)=95:5)和异丙醇(V(hexane):V(2-propanol)=90:10)的流动相中得到了较好的拆分,将样品溶解在和流动相组成相近的溶剂中更利于簇合物拆分,簇合物配体结构对簇合物在固定相上的保留和拆分有重要的影响。在优化条件下,2种金属簇合物分离度均达到1.5以上。     

液相组合化学研究进展

综述了液相组合化学的发展及其在有机合成中的应用。     

Bis(crown-6)calix[4]arene/Cs+ Coordination Chemistry in NPME Solution

NMR spectroscopy was used to show that the symmetry of the crown ether bis(C6) is increased by an increase of the alkali metal cation radius. The EXAFS spectrum demonstrates that a seven oxygen atom coordinated configuration is present in the bis(C6)/Cs⁺/NPME system, where NPME denotes o-nitrophenylmethyl ether. The seventh oxygen in this complex, besides the six crown ether oxygens of bis(C6), may come either from a H₂O molecule or an NO₃⁻ ion.     

All‐Metal Clusters that Mimic the Chemistry of Halogens

Owing to their s²p⁵ electronic configuration, halogen atoms are highly electronegative and constitute the anionic components of salts. Whereas clusters that contain no halogen atoms, such as AlH₄, mimic the chemistry of halogens and readily form salts (e.g., Na⁺(AlH₄)^?), clusters that are solely composed of metal atoms and yet behave in the same manner as a halogen are rare. Because coinage‐metal atoms (Cu, Ag, and Au) only have one valence electron in their outermost electronic shell, as in H, we examined the possibility that, on interacting with Al, in particular as AlX₄ (X=Cu, Ag, Au), these metal atoms may exhibit halogen‐like properties. By using density functional theory, we show that AlAu₄ not only mimics the chemistry of halogens, but also, with a vertical detachment energy (VDE) of 3.98 eV in its anionic form, is a superhalogen. Similarly, analogous to XHX superhalogens (X=F, Cl, Br), XAuX species with VDEs of 4.65, 4.50, and 4.34 eV in their anionic form, respectively, also form superhalogens. In addition, Au can also form hyperhalogens, a recently discovered species that show electron affinities (EAs) that are even higher than those of their corresponding superhalogen building blocks. For example, the VDEs of M(AlAu₄)₂^? (M=Na and K) and anionic (FAuF)? Au? (FAuF) range from 4.06 to 5.70 eV. Au‐based superhalogen anions, such as AlAu₄^? and AuF₂^?, have the additional advantage that they exhibit wider optical absorption ranges than their H‐based analogues, AlH₄^? and HF₂^?. Because of the catalytic properties and the biocompatibility of Au, Au‐based superhalogens may be multifunctional. However, similar studies that were carried out for Cu and Ag atoms have shown that, unlike AlAu₄, AlX₄ (X=Cu, Ag) clusters are not superhalogens, a property that can be attributed to the large EA of the Au atom.     

(TiNi)_x(x=2~4)团簇结构和电子结构

从团簇角度对TiNi形状记忆合金进行了量子化学从头算研究。设计并优化了等原子比(TiNi)x(x=2~4)簇的多种可能几何结构,并对较稳定构型进行电子结构的分析。结果表明,等原子比的(TiNi)n团簇以TiNi成键为主要分子骨架,小团簇有较多能量接近的异构体,TiTi成键对能量降低有较大贡献。     

FT-ICRMS在团簇化学中的应用(Ⅱ)--第一过渡系金属离子与丙炔醇的吸附和反应

近10多年以来,金属离子及其团簇离子在气相中的吸附、催化和反应得到了广泛的关注.在去除溶剂化效应、离子对等干扰的条件下,一些金属有机化合物的反应活性及其催化机理得到了更本质的阐述[1-4].由于过渡金属元素因其外层价电子结构利于插入有机键,使其对大量的有机物都具有反应活性[5].我们探讨了第一过渡系金属离子与丙炔醇的吸附和反应[6].本文介绍利用傅利叶变换离子回旋共振质谱(FT-ICRMS)研究气相中第一过渡系金属离子与丙炔醇的吸附和反应,得到了一些有意义的结果,并讨论了其规律和机理.     

W. Ekardt (ed): Metal clusters. (Wiley Series in Theoretical Chemistry)

Journal of Solid State Electrochemistry -     

Solution Chemistry of Arsenic Anions in the Presence of Metal Cations

The interaction of arsenic(V) and arsenic(III) oxyanions with metal cations was investigated by potentiometry under temperature and ionic strength conditions approaching those prevailing in natural waters. The selection includes the major metal cations and some other ions of high environmental relevance. Ionic pairs [M(As^VO₄)]^?, [M(HAs^VO₄)] and [M(H₂As^IIIO₃)]⁺ formation is suggested for all +2 metal cations, based on the potentiometric results. These ion-pairs between arsenic anions and other metal cations are hardly ever mentioned or taken into account when arsenic speciation in natural waters is considered. These results provide the basis for studying arsenic speciation in natural aquatic systems, on which environmental fate, bioavailability and toxicity of the element depend. Some extrapolations to the conditions of the natural waters are presented as well as some insights into the adsorption process onto hydrous oxides.     

Platinum Group Metal Clusters: From Gas‐Phase Structures and Reactivities towards Model Catalysts

Transition‐metal clusters have long been proposed as model systems to study heterogeneous catalysts. In this Concept article we show how advanced spectroscopic techniques can be used to determine the structures of gas‐phase transition‐metal clusters and their complexes with small molecules. Combined with computational studies, this can help to develop an understanding of the reactivity of these catalytic models.     

Molecular Dynamics Studies of the Kinetics of Phase Changes in Clusters IV： Crystal Nucleation from Molten （NaCl）256 and （NaCl）500 Clusters

Molecular dynamics computer simulation based on the Born-Mayer-Huggins potential function has been carried out to study the effects of duster size and temperature on the nucleation rate of sodium chloride dusters in the temperature range of 580 K to 630 K. Clusters with 256 and 500 NaCl molecules have been studied and the results have been compared with those obtained from 108 molecule dusters. The melting point (MP) of the clusters were observed to increase with the size of the clusters and can be well described by a linear equation MP =1107(37)-1229(23)N^-1/3(N is the number of molecules in the duster).The nucleation rate was found to decrease with increasing the duster size or temperature. Various nucleation theories have been used to interpret the nucleation rates obtained from this molecular dynamics simulation. It is possible to use a constant diffuse interface thickness to interpret the nucleation rate from the diffuse interface theory in the temperature range of this study. However, the interfacinl free energy estimated from classical nucleation theory and diffuse interface theory increases too fast with increasing the temperature while that from Gran-Gunton theory does not change with changing temperatures.The sizes of critical nuclei estimated from all the theories are smaller than those estimated from our simulations.     

金属团簇在单晶表面的稳定性和扩散行为的Monte Carlo研究

The stability and diffusion behaviors of 1.3 MPa Pt, Pd, Ni and Cu clusters supported on Pd(001) surface were studied by the Monte Carlo method. The support surface can strongly influence the stability and diffusion behaviors of the supported clusters. The structure transition temperatures of the supported clusters are much lower than the melting temperatures of their corresponding free clusters due to the vibration coupling between the support and the clusters. The stability of the supported clusters depends on not only the strength of metal support interaction but also the strength of the metal metal interaction. The diffusion constants of supported 1.3 MPa clusters are similar to those of corresponding metal atoms. Combining the diffusion parameters with the critical temperature of the supported clusters, the thermal stability is closely related to the diffusion behaviors of the metal clusters.     

Tris(pentafluoroethyl)difluorophosphorane: A Versatile Fluoride Acceptor for Transition Metal Chemistry

Fluoride abstraction from different types of transition metal fluoride complexes [L_nMF] (M=Ti, Ni, Cu) by the Lewis acid tris(pentafluoroethyl)difluorophosphorane (C₂F₅)₃PF₂ to yield cationic transition metal complexes with the tris(pentafluoroethyl)trifluorophosphate counterion ( FAP anion, [(C₂F₅)₃PF₃]⁻) is reported. (C₂F₅)₃PF₂ reacted with trans-[Ni(iPr₂Im)₂(Ar^F)F] (iPr₂Im=1,3-diisopropylimidazolin-2-ylidene; Ar^F=C₆F₅, 1 a ; 4-CF₃-C₆F₄, 1 b ; 4-C₆F₅-C₆F₄, 1 c ) through fluoride transfer to form the complex salts trans-[Ni(iPr₂Im)₂(solv)(Ar^F)] FAP ( 2 a - c[solv] ; solv=Et₂O, CH₂Cl₂, THF) depending on the reaction medium. In the presence of stronger Lewis bases such as carbenes or PPh₃, solvent coordination was suppressed and the complexes trans-[Ni(iPr₂Im)₂(PPh₃)(C₆F₅)] FAP ( trans -2 a[PPh₃] ) and cis-[Ni(iPr₂Im)₂(Dipp₂Im)(C₆F₅)] FAP ( cis -2 a[Dipp₂Im] ) (Dipp₂Im=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) were isolated. Fluoride abstraction from [(Dipp₂Im)CuF] ( 3 ) in CH₂Cl₂ or 1,2-difluorobenzene led to the isolation of [{(Dipp₂Im)Cu}₂]²⁺2 FAP⁻ ( 4 ). Subsequent reaction of 4 with PPh₃ and different carbenes resulted in the complexes [(Dipp₂Im)Cu(LB)] FAP ( 5 a – e , LB=Lewis base). In the presence of C₆Me₆, fluoride transfer afforded [(Dipp₂Im)Cu(C₆Me₆)] FAP ( 5 f ), which serves as a source of [(Dipp₂Im)Cu)]⁺. Fluoride abstraction of [Cp₂TiF₂] ( 7 ) resulted in the formation of dinuclear [FCp₂Ti(μ-F)TiCp₂F] FAP ( 8 ) (Cp=η⁵-C₅H₅) with one terminal fluoride ligand at each titanium atom and an additional bridging fluoride ligand.