环戊二烯类有机金属含硫族化学的新进展

本文系统地综述了环戊二烯类有机过渡金属含硫族(S, Se, Te) 化学领域的研究现状和进展。参考文献136 篇。     

Synthesis and Chemistry of New Central and Planar Chiral Sulfur-Containing Ferrocenyl Compounds

Abstract

Enantiomerically pure 2-hydroxyalkyl, 2-aminoalkyl and 2-iminoalkyl ferrocenyl p-tolylsulfides are easily prepared in good yields and with complete diastereocontrol from (S)-(2-p-tolylthio)ferrocencarboxyaldehyde. 2-Iminoalkyl ferrocenyl derivatives can be used as ligands in asymmetric catalysis and as starting materials for asymmetric Staudinger reaction.     

Planar Tetracoordinate Silicon in Organic Molecules As Carbenoid-Type Amphoteric Centers: A Computational Study

Designing and synthesizing a stable compound with a planar tetracoordinate silicon (ptSi) center is a challenging goal for chemists. Here, a series of potential aromatic ptSi compounds composed of four conjugated rings shared by a centrally embedded Si atom are theoretically designed and computationally verified. Both Born–Oppenheimer molecular dynamics (BOMD) simulations and potential energy surface scannings verify the high stability and likely existence of these compounds, particularly Si-16-5555 (SiN₄C₈H₈) with 16 π electrons, under standard ambient temperature and pressure. Notably, the Hückel aromaticity rule, which works well for single rings, is inconsistent with the high stability of Si-16-5555 where the 16 p electrons are spread over four five-membered rings fused together. Bonding analyses show that the strong electron donation from the peripheral 12-membered conjugated ring with 16 π electrons to the vacant central atomic orbital Si 3p_z leads to the stabilization for both the ptSi coordination and planar aromaticity. The partial occupation of Si 3p_z results in the peculiar carbenoid-type behaviors for the amphoteric center. By modulating the electron density on the ring with substituent groups, we can regulate the nucleophilic and electrophilic properties of the central Si.     

平面手性化合物的绝对构型及其判定的教学方法

平面手性是手性的一种特殊情形。结合实例详细阐述了手柄化合物、环蕃化合物、反式环烯烃、轮烯类化合物、金属茂化合物等平面手性化合物的绝对构型及判定方法。     

Crystal Chemistry of Complex Carbides and Related Compounds

Numerous metal carbides can be discussed in a rather uniform way by means of structural features, mainly characterized by the mode of linking of octahedral and occasionally trigonal prismatic [M₆C] groups (M = transition element). From this point of view perovskite carbides (M₃M′C, M′ = another transition or A-group element) and derivatives, β-Mn carbides (M₃M′₂C), κ-carbides, carbides with V₃AsC- and Cr₂AlC type structures and derivatives, η-carbides (M₃M′₃C) and carbides having the filled Mn₅Si₃ type structure will be treated. The high stability of these complex carbides is due to the strong bonding M? C and additional bonding of M? M′ atoms forming an ordered parent lattice. Besides the interstitial principle of filling of lattice holes (by isolated carbon atoms), substitution with A-group elements may also take place. Thus in borocarbides extended structural elements occur.     

Coordination Chemistry Dictates the Structural Defects in Lead Halide Perovskites

We show the influence of species present in precursor solution during formation of lead halide perovskite materials on the structural defects of the films. The coordination of lead by competing solvent molecules and iodide ions dictate the type of complexes present in the films. Depending on the processing conditions all PbIS₅⁺, PbI₂S_4, PbI₃S₃^?, PbI₄S₂^2?, PbI₅S₂^3?, PbI₆^4?and 1D (Pb₂I₄)_n chains are observed by absorption measurements. Different parameters are studied such as polarity of the solvent, concentration of iodide ions, concentration of solvent molecules and temperature. It is concluded that strongly coordinating solvents will preferentially form species with a low number of iodide ions and less coordinative solvents generate high concentration of PbI₆^?. We furthermore propose that all these plumbate ions may act as structural defects determining electronic properties of the photovoltaic films.     

基础化学与特色专业化学的承接与协调——以煤化学中“胶质体”为例

针对特色专业化学教学过程中与基础化学知识的承接和协调问题，将繁杂的基础知识和专业理论设定成不同的学习目标，对课程内容重新梳理和组织。以PBL教学理念进行教学设计，强化学习过程中的自我管理和解决问题的能力；以CBL模式进行案例分析，将抽象枯燥的理论知识变成直观、生动、形象的案例，促使学生不断思考该问题或现象出现的原因和机制，克服了普通教学法理论与实践相互联系不足的缺点。对知识点的讲解采取"因-果"相承、"点-面"结合、"抽象-具体"对照的授课方法，获得了良好的教学效果。     

Unravelling the Role of the Pentafluoroorthotellurate Group as a Ligand in Nickel Chemistry

The pentafluoroorthotellurate group (teflate, OTeF₅) is able to form species, for which only the fluoride analogues are known. Despite nickel fluorides being widely investigated, nickel teflates have remained elusive for decades. By reaction of [NiCl₄]²⁻ and neat ClOTeF₅, we have synthesized the homoleptic [Ni(OTeF₅)₄]²⁻ anion, which presents a distorted tetrahedral structure, unlike the polymeric [NiF₄]²⁻. This high-spin complex has allowed the study of the electronic properties of the teflate group, which can be classified as a weak/medium-field ligand, and therefore behaves as the fluoride analogue also in ligand-field terms. The teflate ligands in [NEt₄]₂[Ni(OTeF₅)₄] are easily substituted, as shown by the formation of [Ni(NCMe)₆][OTeF₅]₂ by dissolving it in acetonitrile. Nevertheless, careful reactions with other conventional ligands have enabled the crystallization of nickel teflate complexes with different coordination geometries, i.e. [NEt₄]₂[trans-Ni(OEt₂)₂(OTeF₅)₄] or [NEt₄][Ni(bpyMe₂)(OTeF₅)₃].     

味觉化学之鲜味化学

鲜,作为五味之一,在人们的生活中占有重要地位。介绍了鲜味的概念和生理形成过程,主要鲜味化合物的分类及化学结构,以及鲜味分子呈鲜机制等方面的内容,并且着重从化学的角度对呈鲜化学成分及构效关系进行了梳理和剖析。     

Rotationally Active Ligands: Dialing‐Up the Co‐conformations of a [2]Rotaxane for Metal Ion Binding

A novel [2]rotaxane was constructed that has a bidentate N,N′‐chelate as part of a rigid, H‐shaped axle and a 24‐membered crown ether macrocycle containing six ether O‐atoms and an olefinic group as the wheel. This unique topology produces a ligand with the ability to dial‐up different donor sets for complexation to metal ions by simply rotating the wheel about the axle. The solution and solid‐state structures of the free ligand and complexes with Li⁺ and Cu⁺ show how the ligand adopts different rotational co‐conformations for each. The Li⁺ ion uses the N,N′‐chelate and O‐donors while the Cu⁺ center is coordinated to both O‐donors and the olefinic group. This concept of rotationally active ligands should be possible with a wide variety of donor sets and could find broad application in areas of coordination chemistry, such as catalysis and metal sequestration.     

The Coordination Chemistry of the N-Donor-Substituted Phosphazanes

Phosph(III)azanes, featuring the heterocyclobutane P₂N₂ ring, have now been established as building blocks in main-group coordination and supramolecular compounds. Previous studies have largely involved their use as neutral P-donor ligands or as anionic N-donor ligands, derived from deprotonation of amido-phosphazanes [RNHP(μ-NR)]₂. The use of neutral amido-phosphazanes themselves as chelating, H-bond donors in anion receptors has also been an area of recent interest because of the ease by which the proton acidity and anion binding constants can be modulated, by the incorporation of electron-withdrawing exo- and endo-cyclic groups (R) and by the coordination of transition metals to the ring P atoms. We observed recently that the effect of P,N-chelation of metal atoms to the P atoms of cis-[(2-py)NHP(μ-N^tBu)]₂ (2-py=2-pyridyl) not only pre-organises the N−H functionality for optimum H-bonding to anions but also results in a large increase in anion binding constants, well above those for traditional organic receptors like squaramides and ureas. Here, we report a broader investigation of ligand chemistry of [(2-py)NHP(μ-^tNBu)]₂ (and of the new quinolyl derivative [(8-Qu)NHP(μ-N^tBu)]₂ (8-Qu=8-quinolyl). The additional N-donor functionality of the heterocyclic substituents and its position has a marked effect on the anion and metal coordination chemistry of both species, leading to novel structural behaviour and reactivity compared to unfunctionalized counterparts.     

Structural Chemistry of Borophosphates,Metalloborophosphates, and Related Compounds

A concept for the classification of crystalline (metallo)borophosphates in terms of structural chemistry is proposed and the compounds known to date are classified in an overview. Similarities and differences with (alumo)silicates and Liebau's classification are discussed with respect to the observation that the different borate and phosphate complexes are not interconnected arbitrarily in borophosphates. By combination and extension of existing concepts for silicates and borates a hierarchical system based on oligomeric building units has been developed. The observed connection rules are rationalized and the strong influence of the composition on dimensionality and structural motifs of the formed anions is pointed out. Likewise the effect of OH groups is taken into account by grading anions according to the degree of protonation (ratio O:OH). A general distinction is made between tetrahedral and mixed coordinated borophosphates. Metalloborophosphates are treated separately as special cases of borophosphates. Finally, anion‐substituted compounds, border cases, and borate‐phosphates complete the overview.     

Fundamentals of Silicon Chemistry: Molecular States of Silicon-Containing Compounds

Silicon and its compounds have made possible the design of new materials, which, from computers to space travel, have helped to shape the technology of our 20th century. Conversely, the demands of new technology have stimulated the fast development of silicon chemistry as part of the “renaissance” of inorganic chemistry. This article uses selected examples of predominantly organosilicon compounds to discuss in simplified terms the measurement and assignment of suitable spectroscopic “molecular fingerprints” as well as the resulting benefit for the preparative chemist. The comparison of “equivalent” states of “chemically related” molecules is emphasized, based on perturbation arguments and supporting quantum-chemical models. Special attention is given to the relation between structure and energy, which allows us to understand and to predict the connectivity between and the spatial arrangement of silicon “building blocks”, the energy-dependent electron distribution over the effective nuclear potentials of a molecular framework, and, especially, the partly considerable effects of “silicon substituents” on molecular properties. Future-directed extensions and applications include polysilane band structures, Rydberg states of chromophores containing silicon centers, redox reactions and ion-pair formation of silicon-substituted π systems, and molecular dynamic phenomena in solution or on thermal fragmentation in the gas phase. The main objective is a set of clear and practical rules for interpreting measurements and planning experiments.