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1.
Metallacyclopentadienes and related heterocycles via 1,1‐organoboration of alkyn‐1‐ylmetal compounds
Bernd Wrackmeyer 《Heteroatom Chemistry》2006,17(3):188-208
Metallacyclopentadienes (metalloles) containing M = Si, Ge, Sn, Pb, Ti, Pt can be prepared by 1,1‐organoboration of alkyn‐1‐ylmetal compounds LnM CC R1(R1 = H, alkyl, aryl, silyl, etc; L depends on M, and can be hydrogen, alkyl, aryl, Cl, Br, amino groups, a chelating diphosphane, and one or more L can be again alkynyl groups). These reactions proceed via activation of the M C bond(s) by an electron‐deficient triorganoborane BR3 (R = alkyl, aryl; non‐cyclic, monocyclic, bicyclic, and tricyclic boranes), at first intermolecular and then intramolecular. In the course of these reactions, the M C bonds are cleaved, zwitterionic alkynylborate‐like intermediates are formed, in which the metal‐containing fragments are coordinated side‐on to the CC bonds. In most cases, the 1,1‐organoboration reactions tolerate various functional groups at the alkyne as well as at the metal. The characterization of intermediates and final products by X‐ray structural analysis and by multinuclear magnetic resonance spectroscopy (NMR) is documented and described. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:188–208, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20222 相似文献
2.
Density functional theory study on the possibility of Si‐, Ge‐, and Sn‐doped carbon nanotubes as efficient support materials for platinum 下载免费PDF全文
Guohua Zhang Yun Chen Weiyu Xie Fang Liu Chuntian Chen 《International journal of quantum chemistry》2016,116(7):515-523
PBEPBE‐D3 calculations were performed to investigate how platinum (Pt) interacts with the internal and external surfaces of single‐walled pristine, Si‐, Ge‐, and Sn‐doped (6,6) carbon nanotubes (CNTs). Our calculations showed that atomic Pt demonstrates stronger binding strength on the external surfaces than the internal surface adsorption for the same type of nanotube. In cases of external surface adsorptions, Si‐, Ge‐, and Sn‐doped CNTs show comparable binding energies for Pt, at least 1.40 eV larger than pristine CNT. This enhancement can be rationalized by the strong covalent interactions between Pt and X? C (X = Si, Ge, and Sn) pairs based on structural and projected density of states analysis. In terms of internal surface adsorptions, Ge and Sn doping could significantly enhance the binding of Pt. Pt atom shows much more delocalized and bonding states inside Ge‐ and Sn‐doped CNTs, indicating multiple‐site interaction pattern when atomic Pt is confined inside the nanotubes. However, the internal surface of Si‐doped CNT presents limited enhancement in Pt adsorption with respect to that of pristine CNT because of their similar binding geometries. © 2016 Wiley Periodicals, Inc. 相似文献
3.
Sandeep Yadav Rohit Kumar K. Vipin Raj Prashant Yadav Kumar Vanka Sakya S. Sen 《化学:亚洲杂志》2020,15(19):3116-3121
Despite the explosive growth of germylene compounds as ligands in transition metal complexes, there is a modicum of precedence for the germylene zinc complexes. In this work, the synthesis and characterization of new germylene zinc complexes [PhC(NtBu)2Ge{N(SiMe3)2}→ZnX2]2 (X= Br ( 2 ) and I ( 3 )) supported by (benz)‐amidinato germylene ligands are reported. The solid‐state structures of 2 and 3 have been validated by single‐crystal X‐ray diffraction studies, which revealed the dimeric nature of the complexes, with distorted tetrahedral geometries around the Ge and Zn center. DFT calculations reveal that the Ge–Zn bonds in 2 and 3 are dative in nature. The reaction of 2 with elemental sulfur resulted in the first structurally characterized germathione stabilized ZnBr2 complexes PhC(NtBu)2Ge(=S){N(SiMe3)2}→ZnBr2 ( 5 ). Therefore, the Ge=S in 5 is in‐between Ge–S single and Ge=S double bond length, owing to the coordination of a sulfur lone pair of electrons to ZnBr2. 相似文献
4.
Exploiting Electrostatics To Generate Unsaturation: Oxidative GeE Bond Formation Using a Non π‐Donor Stabilized [R(L)Ge:]+ Cation 下载免费PDF全文
Dr. Arnab Rit Dr. Rémi Tirfoin Prof.Dr. Simon Aldridge 《Angewandte Chemie (International ed. in English)》2016,55(1):378-382
The two‐coordinate germanium cation [(IDipp){(Me3Si)2CH}Ge:]+ has been synthesized, which lacks π‐donor stabilization of the metal center and consequently has a very small HOMO–LUMO gap (187 kJ mol?1). It undergoes a variety of facile oxidative bond‐forming reactions, most notably allowing access to the first examples of Group 14 metal cations containing M?E multiple bonds (E=C, N). The use of an electrostatic (rather than purely steric) strategy to discourage aggregation means that less bulky systems (for example, containing a primary alkylidene fragment, ?CHR) are accessible. 相似文献
5.
Germacyclobutenes: Generation by 1,1‐Carbalumination or 1,1‐Carbagallation and Their Photophysical Properties 下载免费PDF全文
Prof. Dr. Werner Uhl Stefan Pelties Jens Tannert Prof. Dr. Bart Jan Ravoo Prof. Dr. Ernst‐Ulrich Würthwein 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2629-2637
Aluminium‐ and gallium‐functionalised alkenylalkynylgermanes, R12Ge(C?C?R2)[C{E(CMe3)2}?C(H)?R2] (E=Al, Ga), exhibit a close contact between the coordinatively unsaturated Al or Ga atoms and the α‐C atoms of the intact ethynyl groups. These interactions activate the Ge?C(alkynyl) bonds and favour the thermally induced insertion of these C atoms into the E?C(vinyl) bonds by means of 1,1‐carbalumination or 1,1‐carbagallation reactions. For the first time the latter method was shown to be a powerful alternative to known metallation processes. Germacyclobutenes with an unsaturated GeC3 heterocycle and endo‐ and exocyclic C?C bonds resulted from concomitant Ge?C bond formation to the β‐C atoms of the alkynyl groups. These heterocyclic compounds show an interesting photoluminescence behaviour with Stokes shifts of >110 nm. The fascinating properties are based on extended π‐delocalisation including σ*‐orbitals localised at Ge and Al. High‐level quantum chemical DFT and TD‐DFT calculations for an Al compound were applied to elucidate their absorption and emission properties. They revealed a biradical excited state with the transfer of a π‐electron into the empty p‐orbital at Al and a pyramidalisation of the metal atom. 相似文献
6.
Dimethyl Earth‐Metal Heterocycles – Derivatives of Trimethyl‐silylated, ‐germylated, and ‐stannylated Phosphanes and Arsanes – Syntheses, Spectra, and Structures The organo earth‐metal heterocycles [Me2MIII–E(MIVMe3)2]n with MIII = Al, Ga, In; E = P, As; MIV = Si, Ge, Sn and n = 2, 3 (Me = CH3) have been prepared from the dimethyl metal compounds Me2MIIIX (X = Me, H, Cl, OMe, OPh) and the pnicogen derivatives HnE(MIVMe3)3–n (n = 0, 1) according to known preparation methods. The mass, 1H, 13C, 31P, 29Si, 119Sn nmr, as well as the ir and Raman spectra have been discussed comparatively; selected representatives are characterized by X‐ray structure analyses. The dimeric species with four‐membered (E–MIII)2 rings are isotypic and crystallize in the triclinic space group P1, the trimer [Me2In–P(SnMe3)2]3 with a strongly puckered (In–P)3‐ring skeleton crystallizes with two formula units per cell in the same centrosymmetric triclinic space group. 相似文献
7.
Xue Liu Yi Luo Wenting Mao Jingang Jiang Hao Xu Lu Han Junliang Sun Peng Wu 《Angewandte Chemie (International ed. in English)》2020,59(3):1166-1170
A novel crystalline high‐silica zeolite with 12×8‐membered ring (R) channel system is prepared with the aid of the 3D electron diffraction (3D ED) technique. A crystal with the same topology as one of the predicted daughter structures of CIT‐13 germanosilicate, named ECNU‐23 (East China Normal University 23) was coincidentally detected by the 3D ED investigation during the structure characterization of the “pure” powder sample of existing one‐dimension (1D) 10‐R ECNU‐21. By controlling the alkaline‐assisted hydrolysis under moderate conditions, we purified the phase of ECNU‐23 by selectively breaking and removing the chemically weak Ge(Si)‐O‐Ge and metastable Si‐O‐Si bonds. Its structure was determined based on the 3D ED data, and confirmed by high‐resolution TEM images and powder X‐ray diffraction (PXRD) data. The aluminosilicate Al‐ECNU‐23 shows unique catalytic properties in the isomerization/ disproportionation of m‐xylene as solid‐acid catalyst. 相似文献
8.
Post‐Synthesis Stabilization of Germanosilicate Zeolites ITH,IWW, and UTL by Substitution of Ge for Al 下载免费PDF全文
Dr. Mariya V. Shamzhy Dr. Pavla Eliašová Dr. Dana Vitvarová Dr. Maksym V. Opanasenko Daniel S. Firth Prof. Russell E. Morris 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(48):17377-17386
Germanosilicate zeolites often suffer from low hydrothermal stability due to the high content of Ge. Herein, we investigated the post‐synthesis introduction of Al accompanied by stabilization of selected germanosilicates by degermanation/alumination treatments. The influence of chemical composition and topology of parent germanosilicate zeolites ( ITH , IWW , and UTL ) on the post‐synthesis incorporation of Al was studied. Alumination of ITH (Si/Ge=2–13) and IWW (Si/Ge=3–7) zeolites resulted in the partial substitution of Ge for Al (up to 80 %), which was enhanced with a decrease of Ge content in the parent zeolite. In contrast, in extra‐large pore zeolite UTL (Si/Ge=4–6) the hydrolysis of the interlayer Ge?O bonds dominated over substitution. The stabilization of zeolite UTL was achieved using a novel two‐step degermanation/alumination procedure by the partial post‐synthesis substitution of Ge for Si followed by alumination. This new method of stabilization and incorporation of strong acid sites may extend the utilization of germanosilicate zeolites, which has been until now been limited. 相似文献
9.
Patricia J. Nance Niklas B. Thompson Paul H. Oyala Jonas C. Peters 《Angewandte Chemie (International ed. in English)》2019,58(19):6220-6224
Species with 2‐center, 3‐electron (2c/3e?) σ bonds are of interest owing to their fascinating electronic structures and potential for interesting reactivity patterns. Report here is the synthesis and characterization of a pair of zerovalent (d9) trigonal pyramidal Rh and Ir complexes that feature 2c/3e? σ bonds to the Si atom of a tripodal tris(phosphine)silatrane ligand. X‐ray diffraction, continuous wave and pulse electron paramagnetic resonance, density‐functional theory calculations, and reactivity studies have been used to characterize these electronically distinctive compounds. The data available highlight a 2c/3e? bonding framework with a σ*‐SOMO of metal 4‐ or 5dz2 parentage that is partially stabilized by significant mixing with Si (3pz) and metal (5‐ or 6pz) orbitals. Metal‐ligand covalency thus buffers the expected destabilization of transition‐metal (TM)‐silyl σ*‐orbitals by d–p mixing, affording well‐characterized examples of TM–main group, and hence polar, 2c/3e? σ “half‐bonds”. 相似文献
10.
Patricia J. Nance Niklas B. Thompson Paul H. Oyala Jonas C. Peters 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(19):6286-6290
Species with 2‐center, 3‐electron (2c/3e?) σ bonds are of interest owing to their fascinating electronic structures and potential for interesting reactivity patterns. Report here is the synthesis and characterization of a pair of zerovalent (d9) trigonal pyramidal Rh and Ir complexes that feature 2c/3e? σ bonds to the Si atom of a tripodal tris(phosphine)silatrane ligand. X‐ray diffraction, continuous wave and pulse electron paramagnetic resonance, density‐functional theory calculations, and reactivity studies have been used to characterize these electronically distinctive compounds. The data available highlight a 2c/3e? bonding framework with a σ*‐SOMO of metal 4‐ or 5dz2 parentage that is partially stabilized by significant mixing with Si (3pz) and metal (5‐ or 6pz) orbitals. Metal‐ligand covalency thus buffers the expected destabilization of transition‐metal (TM)‐silyl σ*‐orbitals by d–p mixing, affording well‐characterized examples of TM–main group, and hence polar, 2c/3e? σ “half‐bonds”. 相似文献
11.
Silanylidene and Germanylidene Anions: Valence‐Isoelectronic Species to the Well‐Studied Phosphinidene 下载免费PDF全文
Dr. Mujahuddin M. Siddiqui Dr. Soumen Sinhababu Sayan Dutta Dr. Subrata Kundu Paul Niklas Ruth Annika Münch Dr. Regine Herbst‐Irmer Prof. Dietmar Stalke Dr. Debasis Koley Prof. Herbert W. Roesky 《Angewandte Chemie (International ed. in English)》2018,57(36):11776-11780
The reduction of TipMCl3 (Tip=2,4,6‐triisopropylphenyl) (M=Si, Ge) with KC8 in the presence of cyclic alkyl(amino) carbene (cAAC) afforded the acyclic silanylidene and germanylidene anions in the form of potassium salt [K(cAAC)MTip]2 (M=Si ( 1 ); Ge ( 2 )). The silanylidene and germanylidene anions are valence‐isoelectronic to the well‐studied phosphinidene and are a new class of acyclic anions of Group 14. Compounds 1 and 2 were isolated and well characterized by NMR and single‐crystal X‐ray structure analysis. Furthermore, the structure and bonding of compounds 1 and 2 was investigated by computational methods. 相似文献
12.
The Assembly‐Disassembly‐Organization‐Reassembly Mechanism for 3D‐2D‐3D Transformation of Germanosilicate IWW Zeolite 下载免费PDF全文
Pavla Chlubná‐Eliášová Yuyang Tian Dr. Ana B. Pinar Dr. Martin Kubů Prof. Jiří Čejka Prof. Russell E. Morris 《Angewandte Chemie (International ed. in English)》2014,53(27):7048-7052
Hydrolysis of germanosilicate zeolites with the IWW structure shows two different outcomes depending on the composition of the starting materials. Ge‐rich IWW (Si/Ge=3.1) is disassembled into a layered material (IPC‐5P), which can be reassembled into an almost pure silica IWW on treatment with diethoxydimethylsilane. Ge‐poor IWW (Si/Ge=6.4) is not completely disassembled on hydrolysis, but retains some 3D connectivity. This structure can be reassembled into IWW by incorporation of Al to fill the defects left when the Ge is removed. 相似文献
13.
We discuss the dynamic solid‐state properties of crystalline phases E(XMe3)4 as seen by solid‐state NMR and powder X‐ray diffraction. In the first part we will qualitatively describe some of the NMR tools suitable for such investigations. In the second part we will give examples from the group of solid compounds E(XMe3)4 with E = C, Si, Ge and X = Si, Sn. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
14.
Genevieve Cerveau Ernesto Colomer Robert J.P. Corriu 《Journal of organometallic chemistry》1982,236(1):33-52
The cleavages of some new optically active complexes containing CoSi (orGe), MnSi (orGe), ReGe and WGe bonds are described. Electrophiles cleave the CoSi bond with good retention of configuration at silicon, while the MnSi bond is not cleaved under the same conditions. The M′Si and M′Ge bonds (where M' transition metal) are cleaved by nucleophiles with retention or inversion of configuration. In the case of triginal bipyramidal geometry (cobalt complexes) the stereochemical outcome of the reaction is strongly dependent upon electronic effects, the size of the ligand trans to the CoSi (orGe) bond, and the nature of the nucleophilic reagant, in accord with the general rules for nucleophilic substitution at silicon. In contrast the transition metalsilicon orgermanium bonds in the octahedral complexes of manganese, rhenium and tungsten are always cleaved with poor retention of configuration regardless of the nature of the ligands or the nucleophilic reagent. The results provide the first cases in which the stereochemistry of nucleophilic displacement at silicon is independent of the electronic features of both the leaving group and the nucleophile. 相似文献
15.
Dr. Israel Fernández Prof. Dr. F. Matthias Bickelhaupt Prof. Dr. Fernando P. Cossío 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(39):12395-12403
To understand the factors that control the activation barrier of type‐I 1,2‐dyotropic reactions (X‐EH2‐CH2‐X*→X*‐EH2‐CH2‐X, with E=C and Si, X=H, CH3, SiH3, F to I) and trends therein as a function of the migrating groups X, we have explored ten archetypal model reactions of this class using relativistic density functional theory (DFT) at ZORA‐OLYP/TZ2P. The main trends in reactivity are rationalized using the activation strain model of chemical reactivity, which had to be extended from bimolecular to unimolecular reactions. Thus, the above type‐I dyotropic reactions can be conceived as a relative rotation of the CH2CH2 and [X???X] fragments in X‐CH2‐CH2‐X. The picture that emerges from these analyses is that reduced C? X bonding in the transition state is the origin of the reaction barrier. Also the trends in reactivity on variation of X can be understood in terms of how sensitive the C? X interaction is towards adopting the transition‐state geometry. A valence bond analysis complements the analyses and confirms the picture emerging from the activation strain model. 相似文献
16.
The nature of structure and bonding between transition metal and mixed Si‐Ge tetramers: A 20‐electron superatom system 下载免费PDF全文
A novel superatom species with 20‐electron system, SixGeyM+ (x + y = 4; M = Nb, Ta), was properly proposed. The trigonal bipyramid structures for the studied systems were identified as the putative global minimum by means of the density functional theory calculations. The high chemical stability can be explained by the strong p‐d hybridization between transition metal and mixed Si‐Ge tetramers, and closed‐shell valence electron configuration [1S21P62S21D10]. Meanwhile, the chemical bondings between metal atom and the tetramers can be recognized by three localized two‐center two‐electron (2c‐2e) and delocalized 3c‐2e σ‐bonds. For all the doped structures studied here, it was found that the π‐ and σ‐electrons satisfy the 2(N + 1)2 counting rule, and thus these clusters possess spherically double (π and σ) aromaticity, which is also confirmed by the negative nucleus‐independent chemical shifts values. Consequently, all the calculated results provide a further understanding for structural stabilities and electronic properties of transition metal‐doped semiconductor clusters. © 2016 Wiley Periodicals, Inc. 相似文献
17.
Preparation, Characterization, and Structure of Functionalized Fluorophosphaalkenes of the Type R3E–P=C(F)NEt2 (R/E = Me/Si, Me/Ge, CF3/Ge, Me/Sn) P‐functionalized 1‐diethylamino‐1‐fluoro‐2‐phosphaalkenes of the type R3E–P=C(F)NEt2 [R/E = Me/Si ( 2 ), Me/Ge ( 3 ), CF3/Ge ( 4 ), Me/Sn ( 5 )] are prepared by reaction of HP=C(F)NEt2 ( 1 , E/Z = 18/82) with R3EX (X = I, Cl) in the presence of triethylamine as base, exclusively as Z‐Isomers. 2–5 are thermolabile, so that only the more stable representatives 2 and 4 can be isolated in pure form and fully characterized. 3 and 5 decompose already at temperatures above –10 °C, but are clearly identified by 19F and 31P NMR‐measurements. The Z configuration is established on the basis of typical NMR data, an X‐ray diffraction analysis of 4 and ab initio calculations for E and Z configurations of the model compound Me3Si–P=C(F)NMe2. The relatively stable derivative 2 is used as an educt for reactions with pivaloyl‐, adamantoyl‐, and benzoylchloride, respectively, which by cleavage of the Si–P bond yield the push/pull phosphaalkenes RC(O)–P=C(F)NEt2 [R = tBu ( 6 ), Ad ( 7 ), Ph ( 8 )], in which π‐delocalization with the P=C double bond occurs both with the lone pair on nitrogen and with the carbonyl group. 相似文献
18.
Carbene Homologues of Germanium, Tin, and Lead with 2‐substituted N ‐Pyrrolyl Ligands A series of germylenes, stannylenes, and plumbylenes could be prepared by reacting the appropriate bis(trimethylsilyl)amino‐substituted carbene homologue E[N(SiMe3)2]2 (E = Ge, Sn, and Pb) with an α‐carbonyl substituted pyrrole derivative under elimination of bis(trimethylsilyl)amine. The isolated compounds have been analysed spectroscopically, and the resulting NMR and IR data were contrasted with parameters obtained from quantumchemical calculations. The good agreement between experimental and theoretical results gives us the opportunity to discuss the vibrations in more detail, particularly those in which the group 14 element is involved. X‐ray crystal structure analyses obtained for five examples show the title compounds essentially to be monomers with primary E–N bonds and, in addition to that, coordinative E ← O contacts. 相似文献
19.
Klaus Weber Klaus Korn Andrea Schorm Jennifer Kipke Martin Lemke Alexander Khvorost Klaus Harms Jrg Sundermeyer 《无机化学与普通化学杂志》2003,629(5):744-754
The focus of the current report lies on recent developments of synthetic methods applied to the synthesis of some high‐valent complexes containing the nitrido functionality [N]3— as a link between a group 4, 5 or 6 transition metal and a main group element E (E = B, Si, Ge, P, S). Emphasis is put on results, that have been obtained within the “Schwerpunktprogramm “Nitridobrücken” funded by the Deutsche Forschungsgemeinschaft. The synthetic methods include condensation reactions of reactive chloro and oxo complexes (M = V, Nb, Ta, Cr, Mo, W) with silylamines, sulfonylamides, with N‐silyl and N‐lithio iminophosphoranes, furthermore methatesis reactions of oxo complexes with N‐sulfonyl sulfinyl amides (M = V, Cr, Mo, W), the oxidative addition of element azides to d2 metal centers (M = V, W), and finally transamination reactions of N‐H iminophosphoranes with amido complexes (M = Ti, Sm). 相似文献
20.
The first silicon analogues of carbonic (carboxylic) esters, the silanoic thio‐, seleno‐, and tellurosilylesters 3 (Si?S), 4 (Si?Se), and 5 (Si?Te), were prepared and isolated in crystalline form in high yield. These thermally robust compounds are easily accessible by direct reaction of the stable siloxysilylene L(Si:)OSi(H)L′ 2 (L=HC(CMe)2[N(aryl)2], L′=CH[(C?CH2)‐CMe][N(aryl)]2; aryl=2,6‐iPr2C6H3) with the respective elemental chalcogen. The novel compounds were fully characterized by methods including multinuclear NMR spectroscopy and single‐crystal X‐ray diffraction analysis. Owing to intramolecular N→Si donor–acceptor support of the Si?X moieties (X=S, Se, Te), these compounds have a classical valence‐bond N+–Si–X? resonance betaine structure. At the same time, they also display a relatively strong nonclassical Si?X π‐bonding interaction between the chalcogen lone‐pair electrons (nπ donor orbitals) and two antibonding Si? N orbitals (σ*π acceptor orbitals mainly located at silicon), which was shown by IR and UV/Vis spectroscopy. Accordingly, the Si?X bonds in the chalcogenoesters are 7.4 ( 3 ), 6.7 ( 4 ), and 6.9 % ( 5 ) shorter than the corresponding Si? X single bonds and, thus, only a little longer than those in electronically less disturbed Si?X systems (“heavier” ketones). 相似文献