Xenophilic complexes bearing a Tp(R) Ligand, [Tp(R)M--M'Ln] [Tp(R) = Tp(iPr2), Tp(#) (Tp(Me2,4-Br)); M=Ni, Co, Fe, Mn; M'Ln = Co(CO)4, Co(CO)3(PPh3), RuCp(CO)2]: the two metal centers are held together not by covalent interaction but by electrostatic attraction

A series of dinuclear complexes, [Tp(R)M--M'L(n)] [Tp(iPr(2) )M--Co(CO)(4) (1; M=Ni, Co, Fe, Mn); Tp(#)M--Co(CO)(4) (1'; M=Ni, Co); Tp(#)Ni--RuCp(CO)(2) (3')] (Tp(iPr(2) )=hydrotris(3,5-diisopropylpyrazolyl)borato; Tp(#) (Tp(Me(2),4-Br))=hydrotris(3,5-dimethyl-4-bromopyrazolyl)borato), has been prepared by treatment of the cationic complexes [Tp(iPr(2) )M(NCMe)(3)]PF(6) or the halo complexes [Tp(#)M--X] with the appropriate metalates. Spectroscopic and crystallographic characterization of 1-3' reveals that the tetrahedral, high-spin Tp(R)M fragment and the coordinatively saturated carbonyl-metal fragment (M'L(n)) are connected only by a metal-metal interaction and, thus, the dinuclear complexes belong to a unique class of xenophilic complexes. The metal-metal interaction in the xenophilic complexes is polarized, as revealed by their nu(CO) vibrations and structural features, which fall between those of reference complexes: covalently bonded species [R--M'L(n)] and ionic species [M'L(n)](-). Unrestricted DFT calculations for the model complexes [Tp(H(2) )Ni--Co(CO)(4)], [Tp(H(2) )Ni--Co(CO)(3)(PH(3))], and [Tp(H(2) )Ni--RuCp(CO)(2)] prove that the two metal centers are held together not by covalent interactions, but by electrostatic attractions. In other words, the obtained xenophilic complexes can be regarded as carbonylmetalates, in which the cationic counterpart interacts with the metal center rather than the oxygen atom of the carbonyl ligand. The xenophilic complexes show divergent reactivity dependent on the properties of donor molecules. Hard (N and O donors) and soft donors (P and C donors) attack the Tp(R)M part and the ML(n) moiety, respectively. The selectivity has been interpreted in terms of the hard-soft theory, and the reactions of the high-spin species 1-3' with singlet donor molecules should involve a spin-crossover process.     

Conformational state of benzilidene aniline derivatives from ab initio calculation and NMR spectroscopy data

Quantum chemical calculations of the structure and conformational state of a number of Shiff bases have been performed. ¹³C NMR spectra of investigated molecules were calculated and compared with experimental data to test verification of the used calculation model. The effect of terminal substituents on the conformation of azomethines and a relation between the conformation and ¹³C NMR chemical shift were examined.     

钐(II)类卡宾CH3SmCH2I与乙烯环丙烷化反应及溶剂化效应的理论研究

用密度泛函B3LYP方法研究了过渡金属钐类卡宾与乙烯的环丙烷化反应的机理. 对钐类卡宾试剂CH₃SmCH₂I和CH₂CH₂反应的反应物、中间体、过渡态和产物构型的全部结构几何参数进行了优化, 并计算了THF溶液的溶剂化效应, 用内禀反应坐标(IRC)计算和频率分析方法, 对过渡态进行了验证. 结果表明: CH₃SmCH₂I与CH₂CH₂环丙烷化反应按亚甲基转移机理(通道A)和卡宾金属化机理(通道B)都可以进行, 与锂类卡宾的反应机理相同, 通道A比通道B反应的势垒降低了14.65 kJ/mol. 溶剂化效应使通道B比通道A的反应势垒大幅度提高, 更有利于反应沿通道A进行, 而不利于通道B.     

The crystal structure of Fe(SeO2OH)(SeO4)·H2O

Summary The crystal structure of the hydrothermally synthesized compound Fe(SeO₂OH) (SeO₄) · H₂O was determined by single crystal diffraction methods:a=8.355(2) Å,b=8.696(2) Å,c=9.255(2) Å, =93.72(1)°,V=670.95 ų;Z=4, space group P2₁/c,R=0.029,R _w=0.027 for 2430 independent reflections (sin /0.76 Å^–1). Isolated FeO₅(H₂O)-octahedra share five corners with [SeO₂OH] and [SeO₄] groups to form sheets parallel to (100). These sheets are interconnected via hydrogen bonds only.

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Die Kristallstruktur von Fe(SeO₂OH)(SeO₄)·H₂O

Zusammenfassung Die Kristallstruktur der hydrothermal dargestellten Verbindung Fe(SeO₂OH) (SeO₄)·H₂O wurde mittels Einkristallbeugungsmethoden bestimmt:a=8.355(2) Å,b=8.696(2) Å,c=9.255(2) Å, =93.72(1)°,V=670.95 ų;Z=4, Raumgruppe P2₁/c,R=0.029,R _w=0.027 für 2 430 unabhängige Reflexe (sin / 0.76 Å^–1). Isolierte FeO₅(H₂O)-Oktaeder teilen fünf Ecken mit [SeO₂OH]- und [SeO₄]-Gruppen, wobei sie Schichten parallel (100) bilden. Diese Schichten sind nur über Wasserstoffbrücken miteinander verbunden.

     

Transport and Fate of Organic Compounds in the Global Environment

The role of chemistry in our soon-to-be global industrial society requires a global perspective for the discussion of the uptake, transport, and conversion of chemical compounds in the environment. The fate of organic compounds in the volume flow of the atmosphere and hydrosphere can be categorized into transport pathways and adjustments of equilibria in the multiphase system atmosphere-oceans-land surface. The global volume flow in the atmosphere (wind, areas of high and low pressure) and in the hydrosphere (rivers, circulation of water in lakes, ocean currents) alone would account for the transport of organic compounds if they were stable and if all these compounds were molecularly distributed in these phases. However, this particular case is observed only for volatile chlorofluorocarbons and tetrachloromethane. For most organic compounds, complex adsorption/desorption processes on finely dispersed particle phases in the air and water as well as abiotic and biotic transformations determine the transport behavior. The global fate of a compound includes its accumulation as well as its decomposition in defined environmental compartments. Both phenomenon may have long-term consequences in the af-fected areas; this is indicated by the accumulation of polychlorobiphenyls and analogous compounds in marine mammals and deep-sea fauna, and is evident in the decomposition of chlorofluorocarbons in the stratosphere. The accepted definition of the level of a risk, the product of the probability of an event and the potential amount of damage, takes on a new dimension when viewed from a global perspective-especially when one further connects the extent of the damage to the possible means of correction. It is the responsibility of scientists to point out the irreparable regional to global consequences directly and indirectly connected to the production of chemicals and to provide suggestions for prevention. Politicians can only react by applying their methods to limit the damage; however, they cannot generate any solutions based on science.     

Cation-crown ether complex formation in water. II. Alkali and alkaline earth cations and 12-crown-4, 15-crown-5, and 18-crown-6

The stability constants and the partial molal volume and isentropic partial molal compressibility changes of complex formation between cations and crown ethers in water at 25°C are presented. The cations involved are Na⁺, K⁺, Rb⁺, Cs⁺, Ca²⁺, and Ba²⁺, and the crown ethers are 12-crown-4, 15-crown-5, and 18-crown-6. Values of V of complex formation have been discussed in terms of two simple models, one based on the scaled particle theory, and the others on the Drude-Nernst continuum model. The results indicate that the charge of the potassium cation in 18-crown-6 is especially well screened from the water. On this basis hydration numbers of complexed cations have been calculated. This shows that the size of the cation compared to the crown ether hole is important for the contacts between complexed cations and water.     

2-溴丙酸气相热消除反应的机理

用密度泛函（DFT）方法,在B3LYP/6-31G**水平上对2-溴丙酸气相消除反应机理进行了研究.计算表明,反应主要是通过半极化五元环结构过渡态进行的,羧基上的氢原子协助溴原子离去,羧基氧原子帮助稳定过渡态.在B3LYP/6-311＋＋G(3df,3pd)水平上对B3LYP/6-31G**优化的几何构型进行了单点能计算,计算所得反应的速度控制步骤的活化能为189.461 kJ•mol－1,偏离实验值((180.3±3.4) kJ•mol－1)5.08％.     

Finkelstein Reaction in Functionalized Crown-ether Ionic Liquids

Recent years, crown ethers have been used in many fields, including phase transfer catalysis, chromatography stationary phase, ionselective electrode, and concentration of metal ions, etc1.. However, the toxicity of free crown ethers makes them unsuitable for industrial use2. Introduction of a crown ether as a functional group to functionalized ionic liquids has been reported3. These functionalized ionic liquids will combine the excellent properties of crown ether and ionic liquids without los…     

次级键与晶体中锑(III)螯合物配位多面体研究

考虑立体活性孤对电子附近次级键配位原子的贡献, 对文献报道的三十个氨基多羧酸锑(III)螯合物的晶体结构中配位多面体描述进行了全面的修正. 配位多面体的几何构型指定采用了单位球内截多面体的两面角判据及其相关的ANVPDA程序. 所有配位多面体几何构型的修正均得到了键价计算的有力支持.     

次级键与晶体中锑(III)螯合物配位多面体研究

考虑立体活性孤对电子附近次级键配位原子的贡献,对文献报道的三十个氨基多羧酸锑(III)螯合物的晶体结构中配位多面体描述进行了全面的修正.配位多面体的几何构型指定采用了单位球内截多面体的两面角判据及其相关的ANVPDA程序.所有配位多面体几何构型的修正均得到了键价计算的有力支持.