Ga2Br2R2 und Ga3I2R3 [R = C(SiMe3)3] — zwei neue elementorganische Galliumsubhalogenide mit einer bzw. zwei Ga‐Ga‐Bindungen

Ga₂Br₂R₂ and Ga₃I₂R₃ [R = C(SiMe₃)₃] — Two New Organoelement Subhalides of Gallium Containing One or Two Ga‐Ga Single Bonds The oxidation of the tetrahedral tetragallium cluster Ga₄[C(SiMe₃)₃]₄ ( 1 ) with elemental bromine in the presence of AlBr₃ yielded the corresponding gallium subhalide Ga₂Br₂R₂ [ 4 , R = C(SiMe₃)₃], which remains monomer even in the solid state and in which the Ga^II atoms are connected by a short Ga‐Ga single bond [243.2(2) pm]. The analogous diiodide Ga₂I₂R₂ ( 3 ), which was obtained on a similar route by our group only recently, did not react with lithium tert‐butanolate by substitution as originally expected. Instead, partial disproportionation occurred with the formation of the trigallium diiodide Ga₃I₂R₃ ( 6 ), in which three Ga atoms are connected by two Ga‐Ga single bonds (255.1 pm on average). Both terminal Ga atoms have a coordination number of four owing to the bridging function of both iodine atoms, while the inner one which has an oxidation number of +1 remains coordinatively unsaturated. An average oxidation state of 1.66 resulted for all atoms of the chain. The Ga^III compound {[GaI(R)(OCMe₃)(OH)]Li}₂ ( 7 ) was isolated as the second product of the disproportionation. It is a dimer in the solid state via Li‐O bridges and shows a hindered rotation of its tert‐butyl group.     

Synthesis,structural and biocidal activity studies of triorganotin(IV) compounds of some N-protected amino-acids

Seven new triorganotin(IV) complexes of the type R₃SnL (L=N-phthaloyl derivatives of glycine, DL-alanine or N-acetyl- and N-benzoyl-glycine and -cysteine; R-n-C₄H₉ or C₆H₅) have been prepared by reacting the sodium salt of the ligand and the triorganotin(IV) chloride in 1:1 molar ratio in methanol. The complexes have been characterized by elemental analysis, molecular mass determination, IR and ¹H NMR spectroscopy. The complexes are monomeric in molten camphor and are moderateely soluble in the common organic solvents. The spectral data support cis five-coordinate complexes with an unsymmetrical bidentate coordination of the carboxylate group to tin. The complexes exhibit some insecticidal effect on Bean Weevils (Sitophilus granaria) even at low concentration and they also show fungicidal activity on Aspergillus niger and Helminthosporium taulosum. Some of the complexes are found to be more effective than tri-n-butyltin and triphenyltin chlorides.     

氟化钾催化含氢烷氧基硅烷的歧化反应

氟化钾催化含氢烷氧基硅烷的歧化反应张增佑，尚坚，周秀中（南开大学元素有机化学研究所化学系，天津，５０００７１）关键词歧化反应，氟化物，催化，烷氧基硅烷早在７０年代初期Ａｋｌｉｒｅｍ［１］就报道了氟化物可催化硅氢化物醇解。关于氟化物活化Ｓｉ—Ｈ键的实质...     

Short communication: Stille coupling reactions of functionalized triorganotin halides

Convenient conditions for the Stille coupling of halide‐bearing triorganotin compounds, which do not normally react under typical Stille reaction conditions, are presented. The coupling of vinylstannanes with allyl bromide using palladium(II) catalysis is accomplished under fluoride assistance to give the substituted 2,5‐hexadien‐1‐ols in Z‐configuration. Copyright © 2004 John Wiley & Sons, Ltd.     

Lewis Acid-Promoted Reduction of Bis(triorganotin) Oxides to Hexaorganoditins

Hexalkylditin is prepared by a Lewis acid-promoted (MgCl₂) reductive reaction of bis(trialkyltin) oxide using magnesium metal as reducing agent. Hexabutyl- and hexaphenylditin are synthesized with 95% and 80% yield separately and a radical mechanism is proposed for the reaction condition. Unsymmetric ditin, Bu₃Sn-SnPh₃, was first synthesized by this reductive method.     

箭推法视角下对卤素含氧酸根歧化反应的思考

通过对次氯酸根、溴酸根等卤素含氧酸根在一定条件下歧化反应机理的讨论,以及实验事实辅以密度泛函理论(DFT)、Multiwfn计算,探讨了各种机理的合理性,初步验证了利用有机反应机理阐述无机反应过程的合理性,并探寻如何通过类比有机反应机理系统总结无机反应的规律。     

Isomerization and Disproportionation of 1,2,4-Trimethylbenzene over HY Zeolite

The conversion of 1,2,4-trimethy]benzene (1,2,4-TMB) over HY zeolite was studied at atmosoheric pressure and 200–300 °C by using a fixed-bed, integral-flow reactor. The types and initial selectivities of various products were obtained from plots of product selectivity according to the time-on-stream theory. The primary reaction included the isomerization and the disproportionation; the former led to the simultaneous formation of 1,2.3- and 1,3,5-TMB whereas the latter produced all isomers of xylene and tetramethylbenzene. The relative initial rate of disproportionation to isomerization decreased from 12.6 at 200 °C to 5.47 at 300 °C. The activation energies for the primary reactions were estimated and compared with those in the reaction of 1,2,3-TMB.     

Cross‐linked resins functionalized with triorganotin carboxylates: synthesis,characterization and preliminary catalytic screening in transesterification

Cross‐linked polymers containing triorganotin carboxylate functionalities were synthesized from ionic exchange resins bearing carboxylic groups. The organic tin substituents selected were methyl and butyl in order to ensure different accessibility at the metal centre. The functionalization degree depends on the different substituents and strongly affects the thermal stability of the final product. Catalytic screenings were performed in order to assess the activity of the above resins in transesterification reactions, using ethyl acetate as a substrate, together with differently hindered alcohols. The results obtained point to a negligible role of the bulkiness of tin substituents with a small contribution of the metal atom Lewis acidity in the conversion of the primary alcohol, whereas with secondary and tertiary alcohols the steric hindrance of the reagent strongly affects the conversion of the reacting alcohol. The transesterification process takes place at the liquid–solid interface, so that the catalyst grafted to an insoluble solid support can be completely removed by simple filtration. Copyright © 2005 John Wiley & Sons, Ltd.     

New Reaction Pathway of Superoxide Disproportionation Induced by a Soluble Catalyst in Li-O2 Batteries

Aprotic Li-O₂ battery has attracted considerable interest for high theoretical energy density, however the disproportionation of the intermediate of superoxide (O₂⁻) during discharge and charge leads to slow reaction kinetics and large voltage hysteresis. Herein, the chemically stable ruthenium tris(bipyridine) (RB) cations are employed as a soluble catalyst to alternate the pathway of O₂⁻ disproportionation and its kinetics in both the discharge and charge processes. RB captures O₂⁻ dimer and promotes their intramolecular charge transfer, and it decreases the energy barrier of the disproportionation reaction from 7.70 to 0.70 kcal mol⁻¹. This facilitates the discharge and charge processes and simultaneously mitigates O₂⁻ and singlet oxygen related side reactions. These endow the Li-O₂ battery with reduced discharge/charge voltage gap of 0.72 V and prolonged lifespan for over 230 cycles when coupled with RuO₂ catalyst. This work highlights the vital role of superoxide disproportionation for Li-O₂ battery.     

合成皂石及其交联物在偏三甲苯歧化反应中的催化行为

以羟基铝低聚物与其交联制得柱撑皂石,并在偏三甲苯歧化反应中考察了它们的催化性能.结果表明,催化活性随柱撑皂石表面酸量增加而增加;四甲苯中均四甲苯和二甲苯中邻二甲苯的百分含量皆高于热力学平衡值.催化特性与柱撑皂石的柱密度相关.     

A study of the disproportionation equilibrium for allyldibutyltin(IV) chloride as an approach to understanding the role of organotins in the aquatic environment

The equilibrium: 2 Bu₂(CH₂=CHCH₂)SnCl⇌Bu₂Sn(CH₂=CHCH₂)₂ + Bu₂SnCl₂takes place when the allyltin chloride is stirred in water. This has been chosen as a model to understand the extent as well as the mechanistic pattways of the disproportionation reactions 2 R₃SnX⇌R₄Sn + R₂SnX₂ which are thought to occur in the aquatic environment. The behaviour of Bu₂(CH₂=CHCH₂)SnCl has been studied in various media: water, water-acetone, water-ethanol and water-hexane. It has also been ascertained that Bu₂(CH₂=CHCH₂)SnCI is a product arising at room temperature from the scrambling of Bu₂Sn(CH₂==CHCH₂)₂ and Bu₂SnCI₂ either neat, in organic solvents or also in the presence of water. Equilibrium [1] has been interpreted as arising from a bimolecular interaction between the electrophilic aquo-cation [Bu₂(CH₂=CHCH₂)Sn(H₂O)_n]⁺ and the nucleophilic molecule Bu₂(CH₂=CHCH₂)SnCl. Kinetic studies on R₃SnMe/Me₂SnX₂ (X = Cl, NO₃) systems in alcoholic solvents (R = Me, Et, n-Pr, i-Pr, n-Bu) support the assumption that, in dissociating media, redistribution processes can be promoted by ionic electrophilic species.     

Triggering Electron Transfer in Co(I) Dimers: Computational Evidences for a Reversible Disproportionation Mechanism

An inner-sphere disproportionation mechanism of the Co(I) precursor CoCl(PPh₃)₃ is described through a Density Functional Theory study. The essential role of oleylamine in this process is unravelled. A detailed analysis of the electronic structure of Cobalt dimers of the general formula Co₂Cl₂L_n (L=NH₃ and PH₃) demonstrates that electron transfer is triggered by asymetric coordination of amine and phosphine to stabilize a mixed-valence Co(II)−Co(0) dimer. This is consistent with the HSAB statement that both amine and phosphine ligands are required to stabilize the reaction products, respectively Co(II) and Co(0) centers. We propose a quasi-athermic multi-step disproportionation mechanism with low activation barriers where the electron transfer goes through simple ligand exchanges between Co.     

AlCl歧化反应分解法制备金属铝过程中[AlCl]_n的形成机理

利用密度泛函理论(DFT)中的广义梯度近似(GGA)法,对氧化铝真空还原氯化歧化法制备金属铝的过程中[AlCl]n(n=1-10)团簇的稳定结构、能量和团簇形成过程的过渡态及其振动频率进行了理论研究,预测了其基态结构及成长趋势.结果表明:[AlCl]n(n=1-10)团簇可能存在的结构都是以[Al]n骨架外接n个Cl原子成型,且具有较好的几何对称性;从过渡态计算得到的活化能来看,正过程的活化能总是比逆过程的活化能要小,即[AlCl]n(n=1-10)团簇具有较好的成长趋势.以上研究结果有助于进一步了解用碳热还原氯化歧化法制备金属铝过程中液态金属铝的生成.     

C,N‐chelated triorganotin(IV) diesters of 4‐ketopimelic acid and their fungicidal activity

The set of four triorganotin(IV) diesters of 4‐ketopimelic acid containing {2‐[(CH₃)₂NCH₂]C₆H₄}‐ as a C,N‐chelating ligand was prepared. Their structures were studied by the help of IR, NMR and X‐ray crystallographic techniques in the case of {{2‐[(CH₃)₂NCH₂]C₆H₄}SnPh₂}₂[(OOCCH₂CH₂)₂C?]. All these compounds are monomeric both in solid state and solution with five‐coordinated tin atoms and medium strong intramolecular Sn? N connection. The antimycotical activity of these compound was studied and compared with the triorganotin(IV) derivatives of 4‐ketopimelic acid and antimycotical drugs in clinical use. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis,characterization and antimicrobial activity of triorganotin(IV) derivatives of some bioactive Schiff base ligands

Triorganotin(IV) complexes of the type Me₃Sn[OC(R¹):CH(CH₃)C:NR²OH] and Ph₃Sn[OC(R′):CH(CH₃)C:NR″OH] (R′ = ─CH₃, ─C₆H₅; R″ = ─(CH₂)₂─, ─(CH₂)₃─) have been synthesized by the reactions of trimethyl/phenyltin(IV) chloride with the sodium salt of corresponding Schiff base ligands in unimolar ratio in refluxing tetrahydrofuran. All these compounds have been characterized using elemental analyses and their probable structures have been proposed on the basis of infrared, ¹H NMR, ¹³C NMR, ¹¹⁹Sn NMR and mass spectroscopic studies. In the trimethyltin(IV) derivatives the central tin atom is tetracoordinated, whereas in the analogous triphenyltin(IV)derivatives the central tin atom is pentacoordinated. All these ligands, metal precursors and corresponding triorganotin(IV) complexes have been screened for antimicrobial activities. A comparison of activities of the ligands and their corresponding triorganotin(IV) derivatives has been made. Attempts have also been made to relate the activity to the structure of these compounds.     

Electromotive behaviour of anion selective membranes with triorganotin acetates as ionophores and nucleophiles as additives

The electromotive behaviour of neutral carrier based Cl^–-selective electrodes can be improved if lipophilic nucleophiles are added to the membrane phase containing triorganotin acetates as anion carriers. The addition of about 50 mol-% octadecanethiol to diethyl-n-hexyltin acetate as ionophore leads to improved sensor response times and to slopes of the electrode response function close to the Nernstian behaviour.     

C,N-chelated hexaorganodistannanes, and triorganotin(IV) hydrides and cyclopentadienides

Triorganotin(IV) hydrides and cyclopentadienides as well as hexaorganodistannanes containing the moiety L^CN (2-(N,N-dimethylaminomethyl)phenyl-) as chelating ligand and phenyl, n-butyl or t-butyl substituents were prepared and characterized by NMR and XRD. The compounds reveal trigonal bipyramidal geometry around the central tin atom except for the distannanes in which the tin atom has tetrahedral configuration. The di-n-butyl distannane cannot be oxidized by oxygen or heavier chalcogens and give no tin radical when irradiated by UV light or treated with the TEMPO - free radical at room temperature. L^CN(t-Bu)₂SnH undergoes reaction in solution toward the corresponding distannane. The hydrostannation reaction of L^CN(n-Bu)₂SnH with ferrocenylacetylene was investigated. The CO₂ activation by L^CN(n-Bu)₂SnH was also examined.