共查询到20条相似文献,搜索用时 15 毫秒
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Robin F. Weitkamp Beate Neumann Dr. Hans-Georg Stammler Prof. Dr. Berthold Hoge 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(3):915-920
The reaction of a saline phosphazenium hydroxide hydrate with siloxanes led to a novel kind of silanol-silanolate anions. The weakly coordinating behavior of the cation renders the formation of silanol-silanolate hydrogen bonds possible, which otherwise suffer from detrimental silanolate–oxygen cation interactions. We investigated the influence of various weakly coordinating cations on silanol-silanolate motifs, particularly with regard to different cation sizes. While large cations favor the formation of intramolecular hydrogen bonds resulting in cyclic structures, the less bulky tetramethyl ammonium cation encourages the formation of polyanionic silanol-silanolate chains in the solid state. 相似文献
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T. O. Petersen E. Tausch Dr. J. Schaefer Dr. H. Scherer Prof.Dr. P. W. Roesky Prof.Dr. I. Krossing 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(39):13696-13702
Ion‐like ethylzinc(II) compounds with weakly coordinating aluminates [Al(ORF)4]? and [(RFO)3Al‐F‐Al(ORF)3]? (RF=C(CF3)3) were synthesized in a one‐pot reaction and fully characterized by single‐crystal X‐ray diffraction, NMR and vibrational spectroscopy, and by quantum chemical calculations. The catalytic activity of ion‐like Et‐Zn[Al(ORF)4] in intermolecular hydroamination and in the unusual double hydroamination of anilines and alkynes was investigated. Favorable performance was also found in comparison to the Et2Zn/ [PhNMe2H]+[B(C6F5)4]? system generated in situ at lower catalyst loadings of 2.5 mol %. 相似文献
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Robin F. Weitkamp Beate Neumann Dr. Hans-Georg Stammler Prof. Dr. Berthold Hoge 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(21):6460-6464
The reaction of the strong monophosphazene base with the weakly acidic phenol leads to the formation of a phenol–phenolate anion with a moderately strong hydrogen bond. Application of the more powerful tetraphosphazene base (Schwesinger base) renders the isolation of the corresponding salt with a free phenolate anion possible. This compound represents the first species featuring the free phenolate anion [H5C6-O]−. The deprotonation of phenol derivatives with tetraphosphazene bases represents a great way for the clean preparation of salts featuring free phenolate anions and in addition allows the selective syntheses of hydrogen bonded phenol-phenolate salts. This work presents a phosphazenium phenolate salt with a redox potential of −0.72 V and its capability for the selective activation of the chemically inert greenhouse gas SF6. The performed two-electron reduction of SF6 leads to phosphazenium pentafluorosulfanide ([SF5]−) and fluoride salts. 相似文献
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Christoph Bolli Janis Derendorf Prof. Dr. Carsten Jenne Dr. Harald Scherer Christian P. Sindlinger Bianca Wegener 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13783-13792
The weakly coordinating anion [Me3NB12Cl11]? has been prepared by a simple two‐step procedure. The anion [Me3NB12Cl11]? is easily obtained in batches of up to 20 g by chlorination of the known [H3NB12H11]? anion with SbCl5 at about 190 °C and subsequent N‐methylation with methyl iodide. Starting from Na[Me3NB12Cl11], several synthetically useful salts with reactive cations ([NO]+, [Ph3C]+, and [(Et3Si)2H]+) were prepared. Full spectroscopic (NMR, IR, Raman, TGA, MS) characterization and single‐crystal X‐ray diffraction studies confirmed the identity and purity of the products. The thermal, chemical, and electrochemical stability as well as the basicity of the [Me3NB12Cl11]? anion is similar to that of the structurally related weakly coordinating 1‐carba‐closo‐dodecaborate and closo‐dodecaborate anions. The facile preparation of the [Me3NB12Cl11]? anion and its ideal chemical and physical properties make it a cheap alternative to other classes of weakly coordinating anions. 相似文献
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Robin F. Weitkamp Beate Neumann Hans‐Georg Stammler Berthold Hoge 《Angewandte Chemie (International ed. in English)》2019,58(41):14633-14638
The reaction of a strongly basic phosphazene (Schwesinger base) with water afforded the corresponding metastable hydroxide trihydrate [OH(OH2)3]? salt. This is the first hydroxide solvate that is not in contact with a cation and furthermore one of rare known water‐stabilized hydroxide anions. Thermolysis in vacuum results in the decomposition of the hydroxide salt and quantitative liberation of the free phosphazene base. This approach was used to synthesize the Schwesinger base from its hydrochloride salt after anion exchange in excellent yields of over 97 %. This deprotonation method can also be used for the phosphazene‐base‐catalyzed preparation of the Ruppert–Prakash reagent Me3SiCF3 using fluoroform (HCF3) as the trifluoromethyl building block and sodium hydroxide as the formal deprotonation agent. 相似文献
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Simon Steinhauer Dr. Hans‐Georg Stammler Beate Neumann Nikolai Ignat'ev Prof. Dr. Berthold Hoge 《Angewandte Chemie (International ed. in English)》2014,53(2):562-564
The research area of perfluoroalkylsilanes is still in its infancy. Although there are already many examples of difluorotriorganylsilicates, the first example of a completely characterized trifluorotriorganylsilicate is presented, the dianion [Si(C2F5)3F3]2?. The strongly electron‐withdrawing influence of the pentafluoroethyl groups appears to be a fundamental cause of the stability of this compound. This dianion is also the first structurally characterized example of a tris(pentafluoroethyl)silicon compound. The synthesis and complete characterization of [PPh4]2[Si(C2F5)3F3] and [PPh4][Si(C2F5)3F2] along with the precursor [H(OEt2)2][Si(C2F5)3F2] was achieved from SiCl4 and LiC2F5. 相似文献
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Katherine M. Marczenko Chloe-Louise Johnson Prof. Dr. Saurabh S. Chitnis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(37):8865-8874
We report the synthesis and structural characterization of a neutral PV Lewis acid, P(OC6F5)5, and salts containing the six-coordinate anions [P(OC6F5)5F]− and [P(OC6F5)6]−. The latter anion exhibits a rare example of F–πarene interactions in both the solid and the solution phase, which has been quantitatively studied by variable-temperature (VT) NMR spectroscopy. The Lewis acid strength of P(OC6F5)5 has been assessed through experimental fluoride ion competition experiments and quantum-chemical calculations of its fluoride ion affinity (FIA) and global electrophilicity index (GEI). Our findings highlight the importance of considering solvent effects in electrophilicity calculations, even when neutral Lewis acids are involved, and show a rare divergence between FIA and GEI trends. The coordinating abilities of the [P(OC6F5)6]− and [P(OC6F5)5F]− anions towards the trityl cation, as a prototypical electrophile, have been assessed. 相似文献
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Janis Derendorf Prof. Dr. Carsten Jenne Dr. Mathias Keßler 《Angewandte Chemie (International ed. in English)》2017,56(28):8281-8284
The oxidation of elemental sulfur in superacidic solutions and melts is one of the oldest topics in inorganic main group chemistry. Thus far, only three homopolyatomic sulfur cations ([S4]2+, [S8]2+, and [S19]2+) have been characterized crystallographically although ESR investigations have given evidence for the presence of at least two additional homopolyatomic sulfur radical cations in solution. Herein, the crystal structure of the hitherto unknown homopolyatomic sulfur radical cation [S8].+ is presented. The radical cation [S8].+ represents the first step of the oxidation of the S8 molecule present in elemental sulfur. It has a structure similar to the known structure of [S8]2+, but the transannular sulfur⋅⋅⋅sulfur contact is significantly elongated. Quantum-chemical calculations help in understanding its structure and support its presence in solution as a stable compound. The existence of [S8].+ is also in accord with previous ESR investigations. 相似文献
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Dr. Christian Hering‐Junghans Max Thomas Dr. Alexander Villinger Prof. Dr. Axel Schulz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(18):6713-6717
This work describes the synthesis and full characterization of elusive chloropnictenium ion salts of the type [RAr*N(SiMe)ECl][A] (RAr*=2,6‐(CHPh2)‐4‐R‐C6H2, R=Me, tBu; E=Sb, Bi; A?=GaCl4, Al(OCH(CF3)2)4). In these species the cation is significantly stabilized by weak arene interactions to flanking phenyl groups of the RAr* moiety. In this context the bonding situation has been studied by computational means and the reactivity towards the Lewis base 4‐dimethylaminopyridine (dmap) was investigated. 相似文献
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Hydrophobic Encapsulated Phosphonium Salts—Synthesis of Weakly Coordinating Cations and their Application in Wittig Reactions 下载免费PDF全文
Ralf Moritz Dr. Manfred Wagner Dr. Dieter Schollmeyer Prof. Dr. Martin Baumgarten Prof. Dr. Klaus Müllen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(25):9119-9125
Large and rigid tetraarylphosphonium tetrafluoroborate salts have been synthesized representing weakly coordinating cations with diameters of several nanometers. Divergent dendritic growth by means of thermal Diels–Alder cycloaddition was employed for the construction of the hydrophobic polyphenylene framework up to the third generation. X‐ray crystal structure analysis of first‐generation phosphonium tetrafluoroborate supported the rigidity of the non‐collapsible shell around the phosphorus center and gave insight into solid‐state packing and cation–anion distances. Copper(I)‐catalyzed azide–alkyne ligation served as reliable method for the preparation of a first‐generation triazolylphenyl hybrid phosphonium cation under mild reaction conditions. Furthermore, from the synthesis of triarylbenzylphosphonium bromides, Wittig precursors with unprecedented bulky substituents in the α‐position were accessible. Employment of these precursors under Wittig conditions by treatment with base and subsequent reaction with aldehydes preferentially provided (Z)‐olefins with bulky polyphenylene substituents. 相似文献
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Ahmed K. Hijazi Hui Y. Yeong Yanmei Zhang Eberhardt Herdtweck Oskar Nuyken Fritz E. Kühn 《Macromolecular rapid communications》2007,28(5):670-675
CuII compounds coordinated octahedrally with nitriles and associated with bulky, non‐coordinating counter ions can be applied in the polymerization of isobutene at 30 °C. High yields and a high content of terminal double bonds are reached in the resulting highly reactive polyisobutylenes, while the molecular masses are moderate. Two of the coordinating nitriles are more weakly coordinated than the other four, as can be concluded from an exemplary X‐ray structure and from vibrational spectra, thus providing easily accessible sites for substrate coordination.
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A Janus‐Headed Lewis Superacid: Simple Access to,and First Application of Me3Si‐F‐Al(ORF)3 下载免费PDF全文
Dipl.‐Chem. Michael Rohde Dr. Lutz O. Müller Dr. Daniel Himmel Dr. Harald Scherer Prof. Dr. Ingo Krossing 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(5):1218-1222
Upon reaction of gaseous Me3SiF with the in situ prepared Lewis acid Al(ORF)3, the stable ion‐like silylium compound Me3Si‐F‐Al(ORF)3 1 forms. The Janus‐headed 1 is a readily available smart Lewis acid that differentiates between hard and soft nucleophiles, but also polymerizes isobutene effectively. Thus, in reactions of 1 with soft nucleophiles (Nu), such as phosphanes, the silylium side interacts in an orbital‐controlled manner, with formation of [Me3Si?Nu]+ and the weakly coordinating [F?Al(ORF)3]– or [(FRO)3Al‐F‐Al(ORF)3]– anions. If exchanged for hard nucleophiles, such as primary alcohols, the aluminum side reacts in a charge‐controlled manner, with release of FSiMe3 gas and formation of the adduct R(H)O?Al(ORF)3. Compound 1 very effectively initiates polymerization of 8 to 21 mL of liquid C4H8 in 50 mL of CH2Cl2 already at temperatures between ?57 and ?30 °C with initiator loads as low as 10 mg in a few seconds with 100 % yield but broad polydispersities. 相似文献
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Dr. Thies Olaf Petersen Dustin Simone Prof. Dr. Ingo Krossing 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(44):15847-15855
Attempts to prepare previously unknown simple and very Lewis acidic [RZn]+[Al(ORF)4]? salts from ZnR2, AlR3, and HO?RF delivered the ion‐like RZn(Al(ORF)4) (R=Me, Et; RF=C(CF3)3) with a coordinated counterion, but never the ionic compound. Increasing the steric bulk in RZn+ to R=CH2CMe3, CH2SiMe3, or Cp*, thus attempting to induce ionization, failed and led only to reaction mixtures including anion decomposition. However, ionization of the ion‐like EtZn(Al(ORF)4) compound with arenes yielded the [EtZn(arene)2]+[Al(ORF)4]? salts with arene=toluene, mesitylene, or o‐difluorobenzene (o‐DFB)/toluene. In contrast to the ion‐like EtZn(η3‐C6H6)(CHB11Cl11), which co‐crystallizes with one benzene molecule, the less coordinating nature of the [Al(ORF)4]? anion allowed the ionization and preparation of the purely organometallic [EtZn(arene)2]+ cation. These stable materials have further applications as, for example, initiators of isobutene polymerization. DFT calculations to compare the Lewis acidities of the zinc cations to those of a large number of organometallic cations were performed on the basis of fluoride ion affinity. The complexation energetics of EtZn+ with arenes and THF was assessed and related to the experiments. 相似文献
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《Angewandte Chemie (International ed. in English)》2017,56(11):2880-2884
Truly cationic metallocenes with the parent cyclopentadienyl ligand are so far unknown for the Group 14 elements. Herein we report on an almost “naked” [SnCp]+ cation with the weakly coordinating [Al{OC(CF3)3}4]− and [{(F3C)3CO}3Al−F−Al{OC(CF3)3}3]− anions. [SnCp][Al{OC(CF3)3}4] was used to prepare the first main‐group quadruple‐decker cation [Sn3Cp4]2+ again as the [Al{OC(CF3)3}4]− salt. Additionally, the toluene adduct [CpSn(C7H8)][Al{OC(CF3)3}4] was obtained. 相似文献
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Dr. Yu Kitazawa Mamoru Watanabe Yui Masumoto Mai Otsuka Dr. Kazunori Miyamoto Dr. Atsuya Muranaka Dr. Daisuke Hashizume Dr. Ryo Takita Prof. Dr. Masanobu Uchiyama 《Angewandte Chemie (International ed. in English)》2018,57(6):1501-1504
We designed, synthesized, and characterized two types of dimeric forms of monocarba‐closo‐dodecaborate, namely, a “dumbbell”‐shaped dianion having a C?C bond and a “clackers”‐shaped monoanion having an iodonium linker. The unique architectures of these anionic molecules were established by X‐ray analysis. Spectroscopic analysis, DFT calculations, and reactivity experiments revealed high anionic and chemical stability of both anions, which are crucial properties for weakly coordinating anions. 相似文献