Tunability of the M(II)M(III)/M(II)(2) and M(III)(2)/M(II)M(III) (M=Mn, Co) couples in bis-μ-O,O'-carboxylato-μ-OR bridged complexes

A comparison of the electrochemical properties of a series of dinuclear complexes [M(2)(L)(RCO(2))(2)](+) with M = Mn or Co, L = 2,6-bis(N,N-bis-(2-pyridylmethyl)-sulfonamido)-4-methylphenolato (bpsmp(-)) or 2,6-bis(N,N-bis(2-pyridylmethyl)aminomethyl)-4-tert-butylphenolato (bpbp(-)) and R = H, CH(3), CF(3) or 3,4-dimethoxybenzoate demonstrates: (i) The electron-withdrawing sulfonyl groups in the backbone of bpsmp(-) stabilize the [M(2)(bpsmp)(RCO(2))(2)](+) complexes in their M(II)(2) oxidation state compared to their [M(2)(bpbp)(RCO(2))(2)](+) analogues. Manganese complexes are stabilised by approximately 550 mV and cobalt complexes by 650 mV. (ii) The auxiliary bridging carboxylato ligands further attenuate the metal-based redox chemistry. Substitution of two acetato for two trifluoroacetato ligands shifts redox couples by 300-400 mV. Within the working potential window, reversible or quasi-reversible M(II)M(III)? M(II)(2) processes range from 0.31 to 1.41 V for the [Co(2)(L)(RCO(2))(2)](+/2+) complexes and from 0.54 to 1.41 V for the [Mn(2)(L)(RCO(2))(2)](+/2+) complexes versus Ag/AgCl for E(M(II)M(III)/M(II)(2)). The extreme limits are defined by the complexes [M(2)(bpbp)(CH(3)CO(2))(2)](+) and [M(2)(bpsmp)(CF(3)CO(2))(2)](+) for both metal ions. Thus, tuning the ligand field in these dinuclear complexes makes possible a range of around 0.9 V and 1.49 V for the one-electron E(M(II)M(III)/M(II)(2)) couple of the Mn and Co complexes, respectively. The second one-electron process, M(II)M(III)? M(III)(2) was also observed in some cases. The lowest potential recorded for the E°(M(III)(2)/M(II)M(III)) couple was 0.63 V for [Co(2)(bpbp)(CH(3)CO(2))(2)](2+) and the highest measurable potential was 2.23 V versus Ag/AgCl for [Co(2)(bpsmp)(CF(3)CO(2))(2)](2+).     

ChemInform Abstract: Are Cyclogallenes (M2(GaH)3) (M: Li,Na, K) Aromatic?

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Ion-Exchange Processes M(II) → Fe(III) and Fe(III) → M(II) in Metal Hexacyanoferrate(II) Gelatin-Immobilized Matrices (M = Mn,Co, Ni,Cu, Zn,Cd)

Ion-exchange reactions M²⁺ Fe³⁺ and Fe³⁺ M²⁺ (M = Mn, Co, Ni, Cu, Zn, Cd) were studied in metal(II) hexacyanoferrate(II) gelatin-immobilized matrices M₂[Fe(CN)₆] in contact with aqueous FeCl₃ solutions and Fe₄[Fe(CN)₆]₃ in contact with aqueous MCl₂ solutions. It was shown that in both cases, M²⁺ was replaced by Fe³⁺ and Fe³⁺ was replaced by M²⁺ to some extent, but no complete replacement was observed in the M₂[Fe(CN)₆]–FeCl₃ or Fe₄[Fe(CN)₆]₃–MCl₂ systems under study. No electrophilic substitution Fe³⁺ Mn²⁺ was found to occur in any noticeable degree during the contact of Fe₄[Fe(CN)₆]₃ with aqueous MnCl₂ solutions even when this contact occurred for 1 h and longer.     

Cyclohexylamine) 2 M(CN) 4 ⋅2C 6 H 6 (M = Cd or Hg)

Two new title compounds have been prepared in powder form. Their spectral data are found to be consistent with the structure foundin Hofmann-T_d-type clathrates.     

Total Synthesis of (±) Kadsurenin M

KadsllreIlinM(7s.8s-.1.4.3'-tril1letllop'-7"oxo-n0r-8'.9'-7.0.4'.8.5'-neolignan)u'asisolatedfrollltlleaerialpart0fPiperKadsl1ra(Cl1ois}')0l1\viI'].aCllinesetraditiol1aldrugusedf0rtlletreatll1el1tofil1naI11l11ati0nundrl1eul1laticcol1diti0l1s.Aspartof0urresearcl1xt,0rkontlletotals}'lltllcsisofbe11z0fura11oidncolignans,l"ereportl1eret11efirstlotalsi'ntl1esisofkadsurenil1Masitsrecel11icfonn.Tllep-lltlleticro[1leisdepic1edi1ltl1ef0lloxt'il1gsclleme.3.4-Dilnetl1on'cil1nam}'lcllloride6.readil}'a\…     

Transition-metal-centered nine-membered boron rings: MⓒB9 and MⓒB9(-) (M = Rh, Ir)

We report the observation of two transition-metal-centered nine-atom boron rings, Rh?B(9)(-) and Ir?B(9)(-). These two doped-boron clusters are produced in a laser-vaporization supersonic molecular beam and characterized by photoelectron spectroscopy and ab initio calculations. Large HOMO-LUMO gaps are observed in the anion photoelectron spectra, suggesting that neutral Rh?B(9) and Ir?B(9) are highly stable, closed shell species. Theoretical calculations show that Rh?B(9) and Ir?B(9) are of D(9h) symmetry. Chemical bonding analyses reveal that these complexes are doubly aromatic, each with six completely delocalized π and σ electrons, which describe the bonding between the central metal atom and the boron ring. This work establishes firmly the metal-doped B rings as a new class of novel aromatic molecular wheels.     

An Infrared Spectroscopic Study of Pyrazine- and 4,4′-bipyridyl-Td-type Clathrates: Mn (pyrazine) M(CN)4 benzene (M = Cd or Hg) and Mn (4,4′-bipyridyl) M(CN)4. benzene (M = Zn, Cd or Hg)

The infrared spectra of the title compounds have been reported. The spectral data suggest that the host framework of these compounds are similar to those of the en-T_d-type clathrate compounds. There is good evidence for hydrogen bonding from ligand molecules to benzene molecules as a to hydrogen bond.     

Reactions of ((i)PrO)3M≡M(O(i)Pr)3 (M = Mo, W) with low-coordinate phosphorus compounds. Formation of the first four-membered planar metallacycles, containing an M≡M triple bond

The low-coordinate phosphorus compounds (Me(3)Si)(2)N-P=NSiMe(3), (Me(3)Si)(2)N-P(=S)=N(t)Bu and (Me(3)Si)(2)N-P(=NSiMe(3))(2) react with ((i)PrO)(3)M≡M(O(i)Pr)(3) (M = Mo, W) to form four- and five-membered metallacycles with intact endocyclic or exocyclic M≡M triple bonds. The first four-membered planar metallacycles, containing an M≡M triple bond were obtained in reaction with (Me(3)Si)(2)N-P=NSiMe(3).     

Ylenes in the M(II)→Si(IV) (M=Si, Ge, Sn) coordination mode

The reaction of the methimazolyl (mt, i.e., 2-mercapto-1-methylimidazolide) substituted silane Si(mt)(4) with SnCl(2) and GeCl(2) in dioxane affords the paddlewheel-shaped complexes [ClSi(μ-mt)(4)MCl] (M=Sn (1) and Ge (2), respectively). These compounds represent the first crystallographically characterized hexacoordinate silicon complexes comprising a Sn or Ge atom in the Si coordination sphere. An attempt to synthesize the related silicon compound 3 [ClSi(μ-mt)(4)SiCl] instead afforded the trisilane [ClSi(μ-mt)(4)Si-SiCl(3)] (3a), which provides the first crystallographic evidence for the feasibility of oligosilanes with adjacent hexacoordinate Si atoms. One of the hexacoordinate Si atoms of 3a features the unprecedented (Si(2)S(4))Si skeleton. Natural bonding orbital (NBO) analyses of compounds 1, 2, 3a (and the target compound 3) revealed characteristics of M(II)→Si(IV) (for 2 and 3) or M(I)→Si(IV) (for 3a) dative bonding in the systems with M=Si and Ge, whereas compound 1 exhibits a covalent Sn(III)-Si(III) bond.     

噻吩在M(111)(M=Pd,Pt,Au)表面的吸附(英文)

采用密度泛函理论(DFT),选取DMol3程序模块,对噻吩在M(111)(M=Pd,Pt,Au)表面上的吸附行为进行了探讨.通过对噻吩在不同底物金属上的吸附能、吸附构型、Mulliken电荷布居、差分电荷密度以及态密度的分析发现,噻吩在Pd(111)面上的吸附能最大,Pt(111)面次之,Au(111)面最小.吸附后,噻吩在Au(111)面上的构型几乎保持不变,最终通过S端倾斜吸附于top位;噻吩在Pd(111)及Pt(111)面上发生了折叠与变形,环中氢原子向上翘起,最终通过环平面平行吸附于hollow位.此外,噻吩环吸附后芳香性遭到了破坏,环中碳原子发生sp3杂化,同时电子逐渐由噻吩向M(111)面发生转移,M(111)面上的部分电子也反馈给了噻吩环中的空轨道,这种协同作用最终导致了噻吩分子稳定吸附于M(111)面.     

Electron Paramagnetic Resonance Analysis of La(1-x)M(x)MnO(3+δ) (M = Ce, Sr) Perovskite-Like Nanostructured Catalysts

The physical-chemical properties of some nanostructured perovskite-like catalysts of general formula La(1-x)M(x)MnO(3+δ) (M = Ce, Sr) have been investigated, in particular by using the electron paramagnetic resonance (EPR) technique. We show that the interplay between the -O-Mn(3+)-O-Mn(4+)-O- electron double-exchange and the electron mobility is strictly dependent on the dopant nature and the annealing conditions in air. A relationship between the observed properties of these samples and their activity in the methane flameless catalytic combustion is proposed.     

混配化合物M(α-AP)2(OAc)2(M=Ni、Zn)的室温固相合成及表征

Zn、Ni是重要的生命元素,在人体中属于必需的微量营养元素;金属离子与不同氨基酸形成的混配化合物,在生命活动中具有十分重要的作用,氨基酸中参与配位的主要是氮和羧酸,所以研究含氮和羧酸的混配化合物具有重要意义[1-6].     

Mössbauer study of sodium ferrates(IV) and (VI)

Sodium ferrates(IV) and (VI) were synthesized by the reaction between Fe₂O₃ and Na₂O₂ in a dry oxygen stream. The Mössbauer data for the obtained samples are presented (for Na₂FeO₃–=0.18(2) mm/s; for Na₄FeO₅–=–0.54(2) mm/s). It was shown that pure K₂FeO₄ and Cs₂FeO₄ can be obtained by heating Fe₂O₃ with apropriate alkali metal peroxides.     

过渡金属团簇M20和M20(PMe3)4(M=Cu,Ag,Au)的量子化学理论研究

采用从头计算MP2和DFT理论方法,对过渡金属团簇M20和M20( PMe3)4(M=Cu,Ag,Au)的几何结构、电子结构以及团簇各组成部分之间的结合能进行了研究.所研究的体系具有较大的前线轨道能隙,与C60接近,显示出特别的稳定性.考虑电子相关效应的MP2方法能够对团簇的结构给予可靠的描述.离域泛函GGA对Cu和A...     

Avoided crossings in metal (M)–gas (X) reactions (M = Hg, and X = SiH4, GeH4)

A study of nonadiabatic transitions through avoided crossings between two potential energy curves, associated to the approach of a mercury atom to an organic gas molecule (silane or germane) is presented. We study the Si–H and Ge–H bond breaking in the molecules SiH₄ and GeH₄, which are an important subject in the production of hydrogenated amorphous thin films. We here emphasize the importance of the excited states, the avoided crossings generated during the molecule–metal approach and the nonadiabatic transition probabilities. We have developed a model to extend the Landau–Zener theory utilizing the angle instead of the distance as the main parameter of the reaction, which is particularly adapted for tetrahedral molecules (as silane and germane). The activation process of these molecules requires several stages; first, we solve the Schrödinger equation (within the Born-Oppenheimer approximation) for the metal–molecule system during interaction. We always take into account all those states that can play a role in the reaction, even those that because of their energetic separation from the ground state are forgotten by other groups. The calculations begin at a LCAO-MO approximation and thenceforth variational and perturbative CI including of the order of a million determinants are carried out. Usually, some states of the metal repel the gas molecule and others attract it. This produces a series of avoided crossings among the curves, demanding that the nonadiabatic transition probabilities are obtained. This is the ultimate goal of the present study.     

M(bpy)2+3(M=Fe,Ru,Os)电子结构与相关性质

报导了对配合物Ｍ（ｂｐｙ）＾２＋３（Ｍ＝Ｆｅ,Ｒｕ,Ｏｓ）的量子化学密度泛函法研究的结果。Ｂ３ＬＹＰ／ＬａｎＬ２ＤＺ方法与基组的水平上进行计算,探讨Ｍ（ｂｐｙ）＾２＋３电子结构特征及相关性质,特别是中心原子对配合物的配位键长、光谱性质,电荷布局及化学稳定性等的影响规律,为该类配合物的合成,为分析光、电、催化作用机理提供理论参考。     

M(bpy)2+3(M=Fe,Ru,Os)电子结构与相关性质

报导了对配合物(M=Fe,Ru,Os)的量子化学密度泛函(DFT)法研究的结果.在B3LYP/LanL2DZ方法与基组的水平上进行计算,探讨的电子结构特征及相关性质,特别是中心原子对配合物的配位键长、光谱性质、电荷布居及化学稳定性等的影响规律,为该类配合物的合成,为分析光、电、催化作用机理提供理论参考.     

M(NTEA)配合物的NMR研究

用ＮＭＲ方法研究了氨三乙氧基乙酸（ＮＴＥＡ）的质子解离过程及其与Ｌａ３＋、Ｙ３＋、Ｌｕ３＋和Ｃａ２＋的配合作用．ＮＴＥＡ的氮原子和羧基的质子解离常数分别为８．８和３．０．当ｐＨ＞３．０时，Ｌａ３＋、Ｙ３＋和Ｌｕ３＋配合物能稳定形成（＞５０％），而Ｃａ２＋配合物则需出＞５．在ｐＨ３～６范围内，配合物与配体间的交换反应处于慢－中介交换速率区间，通过变温谱模拟得到了其交换反应的动力学参数．     

M2TNR(M=AG, CHZ)的制备和晶体结构

通过三硝基间苯二酚(TNR,斯蒂酚酸)和氨基胍(AG)重碳酸盐、碳酰肼(CHZ)反应,制备斯蒂酚酸氨基胍和斯蒂酚酸碳酰肼。并用X-射线衍射分析、元素分析、差示扫描量热法和红外光谱对其进行了结构表征。它们的分子式分别为(NH2NHCNHNHNH2)2^+[C6H(NO3)3O2]^2.0.5H2O,(NH2NHCONHNH3)2^+[C6H(NO3)3O2]^2^-,二者都属于单斜晶系,C2/c空间群。     

三元体系MCl-M′Cl-HOAc(25℃)的研究(M,M′=K、Rb、Cs,M≠M′)

测定了25℃下KCl-RbCl-HOAc,KCl-CsCl-HOAc,RbCl-CsCl-HOAc三个体系的溶度数据,绘制了相应的相图以及分配图。第一个体系中只有一种固相存在,属于Roozeboom第Ⅰ型;后两个体系互溶性都有十分明鲜的裂隙,但比以水为溶剂的体系中的互溶性显著增强,二者均属Roozeboom第Ⅳ型。