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1.
Michael Meier Dr. Lei Ji Dr. Jörn Nitsch Dr. Ivo Krummenacher Andrea Deißenberger Dr. Dominic Auerhammer Dr. Marius Schäfer Prof. Dr. Todd B. Marder Prof. Dr. Holger Braunschweig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(18):4707-4712
A novel thiophene-bridged donor–acceptor system was synthesized with a carbazole as donor and a borole as acceptor unit. The borole group was successfully installed via the tin–boron exchange reaction of 1,1-dimethyl-2,3,4,5-tetraphenylstannole with 9-(5-(dibromoboryl)thiophen-2-yl)carbazole. The effect of the borole on the optoelectronic properties of the donor–acceptor system was explored by spectroscopic (UV/Vis and fluorescence spectroscopy), electrochemical (cyclic voltammetry) and theoretical (TD-DFT) methods as well as by modifying its structure. The corresponding donor–acceptor compound bearing the widely employed dimesitylboryl acceptor group was also synthesized for comparison. 相似文献
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Thais R. Cruz Eliada A. Silva Douglas P. Oliveira Daniele M. Martins Patrik D.S. Gois Antonio E.H. Machado Pedro Ivo S. Maia Beatriz E. Goi Benedito S. Lima-Neto Valdemiro P. Carvalho-Jr 《应用有机金属化学》2020,34(5):e5602
Arene ruthenium(II) complexes bearing the cyclic amines RuCl2(η6-p-cymene)(pyrrolidine)] ( 1 ), [RuCl2(η6-p-cymene)(piperidine)] ( 2 ), and [RuCl2(η6-p-cymene)(peridroazepine)] ( 3 ) were successfully synthesized. Complexes 1 – 3 were fully characterized by means of Fourier transform infrared, UV–visible, and NMR spectroscopy, elemental analysis, cyclic voltammetry, computational methods, and one of the complexes was further studied by single crystal X-ray crystallography. These compounds were evaluated as catalytic precursors for ring-opening metathesis polymerization (ROMP) of norbornene (NBE) and atom-transfer radical polymerization (ATRP) of methyl methacrylate (MMA). NBE polymerization via ROMP was evaluated using complexes 1 – 3 as precatalysts in the presence of ethyl diazoacetate (EDA) under different [NBE]/[EDA]/[Ru] ratios, temperatures (25 and 50°C), and reaction times (5–60 min). The highest yields of polyNBE were obtained with [NBE]/[EDA]/[Ru] = 5000/28/1 for 60 min at 50°C. MMA polymerization via ATRP was conducted using 1 – 3 as catalysts in the presence of ethyl-α-bromoisobutyrate (EBiB) as initiator. The catalytic tests were evaluated as a function of the reaction time using the initial molar ratio of [MMA]/[EBiB]/[Ru] = 1000/2/1 at 95°C. The increase in molecular weight as function of time indicates that complexes 1–3 were able to mediate the MMA polymerization with an acceptable rate and some level of control. Differences in the rate of polymerization were observed in the order 3 > 2 > 1 for the ROMP and ATRP. 相似文献
5.
Prof. Dr. Holger Braunschweig Charlotte Brückner Dr. Mehmet Ali Celik Dr. Klaus Dück Dr. Florian Hupp Dr. Thomas Kramer Johannes Krebs Dr. Ivo Krummenacher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(31):11056-11064
Taking advantage of an improved synthesis of [Ti(η6‐C6H6)2], we report here the first examples of ansa‐bridged bis(benzene) titanium complexes. Deprotonation of [Ti(η6‐C6H6)2] with nBuLi in the presence of N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine (pmdta) leads to the corresponding 1,1′‐dilithio salt [Ti(η6‐C6H5Li)2] ? pmdta that enables the preparation of the first one‐ and two‐atom‐bridged complexes by simple salt metathesis. The ansa complexes were fully characterized (NMR spectroscopy, UV/Vis spectroscopy, elemental analysis, and X‐ray crystallography) and further studied electrochemically and computationally. Moreover, [Ti(η6‐C6H6)2] is found to react with the Lewis base 1,3‐dimethylimidazole‐2‐ylidene (IMe) to give the bent sandwich complex [Ti(η6‐C6H6)2(IMe)]. 相似文献
6.
Dipl.‐Chem. Ivo Sarac Prof. Dr. Chris Meier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16421-16426
A fast, high‐yielding and reliable method for the synthesis of DNA‐ and RNA 5′‐triphosphates is reported. After synthesizing DNA or RNA oligonucleotides by automated oligonucleotide synthesis, 5‐chloro‐saligenyl‐N,N‐diisopropylphosphoramidite was coupled to the 5′‐end. Oxidation of the formed 5′‐phosphite using the same oxidizing reagent used in standard oligonucleotide synthesis led to 5′‐cycloSal‐oligonucleotides. Reaction of the support‐bonded 5′‐cycloSal‐oligonucleotide with pyrophosphate yielded the corresponding 5′‐triphosphates. The 5′‐triphosphorylated DNA and RNA oligonucleotides were obtained after cleavage from the support in high purity and excellent yields. The whole reaction sequence was adapted to be used on a standard oligonucleotide synthesizer. 相似文献
7.
Boron as a Powerful Reductant: Synthesis of a Stable Boron‐Centered Radical‐Anion Radical‐Cation Pair 下载免费PDF全文
Dr. Philipp Bissinger Prof. Dr. Holger Braunschweig Dr. Alexander Damme Dr. Christian Hörl Dr. Ivo Krummenacher Dr. Thomas Kupfer 《Angewandte Chemie (International ed. in English)》2015,54(1):359-362
Despite the fundamental importance of radical‐anion radical‐cation pairs in single‐electron transfer (SET) reactions, such species are still very rare and transient in nature. Since diborenes have highly electron‐rich B? B double bonds, which makes them strong neutral reductants, we envisaged a possible realization of a boron‐centered radical‐anion radical‐cation pair by SET from a diborene to a borole species, which are known to form stable radical anions upon one‐electron reduction. However, since the reduction potentials of all know diborenes (E1/2=?1.05/?1.55 V) were not sufficiently negative to reduce MesBC4Ph4 (E1/2=?1.69 V), a suitable diborene, IiPr?(iPr)B?B(iPr)?IiPr, was tailor‐made to comply with these requirements. With a halfwave potential of E1/2=?1.95 V, this diborene ranks amongst the most powerful neutral organic reductants known and readily reacted with MesBC4Ph4 by SET to afford a stable boron‐centered radical‐anion radical‐cation pair. 相似文献
8.
Teemu Näykki Timo Sara-Aho Tero Väisänen Ivo Leito 《International journal of environmental analytical chemistry》2015,95(1):1-15
A novel tool for the investigation of stability of total mercury in water samples is presented. The study focuses on the application of enriched 196Hg stable isotopic reagent for the stability studies. Natural abundance of 196Hg in water samples is only 0.15%. Thus, the use of the 196Hg isotope spike represents a major advantage, when it can be assumed that all the measured isotope is the same as is accurately added by the analyst, and the change in its mass concentration can be followed simply and reliably. Tests were carried out with industrial waste water and two type of the natural water. Cold vapour (CV) inductively coupled plasma mass spectrometer (ICP-MS) technique was applied for the mercury measurements. Monitoring was continued for approximately 100 days. It is commonly advised that the measurement for total mercury in water samples should be carried out within 14 days. In this study the samples were observed to be stable for more than three months, if they were stored at a temperature of 4–6°C. The results of this stability study were in line with the guidance presented in EPA standard 1631. However, the samples were noticed to be stable for a much longer time than is presented in the standard method ISO 17852. 相似文献
9.
Ansa‐Complexes of [Mn(η5‐C5H5)(η6‐C6H6)]: Preparation,Characterization, and Reactivity of [n]Manganoarenophanes (n=1, 2, 3) 下载免费PDF全文
Prof. Dr. Holger Braunschweig Dr. Alexander Damme Dr. Klaus Dück Dr. Marco Fuß Dr. Christian Hörl Dr. Thomas Kramer Dr. Ivo Krummenacher Dr. Thomas Kupfer Valerie Paprocki Christoph Schneider 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14797-14803
We report the synthesis of [n]manganoarenophanes (n=1, 2) featuring boron, silicon, germanium, and tin as ansa‐bridging elements. Their preparation was achieved by salt‐elimination reactions of the dilithiated precursor [Mn(η5‐C5H4Li)(η6‐C6H5Li)]?pmdta (pmdta=N,N,N′,N′,N′′‐pentamethyldiethylenetriamine) with corresponding element dichlorides. Besides characterization by multinuclear NMR spectroscopy and elemental analysis, the identity of two single‐atom‐bridged derivatives, [Mn(η5‐C5H4)(η6‐C6H5)SntBu2] and [Mn(η5‐C5H4)(η6‐C6H5)SiPh2], could also be determined by X‐ray structural analysis. We investigated for the first time the reactivity of these ansa‐cyclopentadienyl–benzene manganese compounds. The reaction of the distannyl‐bridged complex [Mn(η5‐C5H4)(η6‐C6H5)Sn2tBu4] with elemental sulfur was shown to proceed through the expected oxidative addition of the Sn?Sn bond to give a triatomic ansa‐bridge. The investigation of the ring‐opening polymerization (ROP) capability of [Mn(η5‐C5H4)(η6‐C6H5)SntBu2] with [Pt(PEt3)3] showed that an unexpected, unselective insertion into the Cipso?Sn bonds of [Mn(η5‐C5H4)(η6‐C6H5)SntBu2] had occurred. 相似文献
10.
Ring Expansions of Boroles with Diazo Compounds: Steric Control of C or N Insertion and Aromatic/Nonaromatic Products 下载免费PDF全文
Prof. Dr. Holger Braunschweig Dr. Florian Hupp Dr. Ivo Krummenacher Lisa Mailänder Florian Rauch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(49):17844-17849
Access to novel imine‐substituted 1,2‐azaborinines, as well as highly arylated boracyclohexa‐3,5‐dienes has been developed by ring expansion of boroles with diazoalkanes with varying degrees of steric bulk. The formation of a diazoalkane intermediate is also discussed for the reaction of ortho‐brominated p‐tolyl‐azide with 1,2,3,4,5‐pentaphenylborole. Structural details as well as UV/Vis spectroscopic and cyclic voltammetric data are provided. These boron‐containing heterocycles have the potential to serve as building blocks for boron‐containing materials. 相似文献