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1.
The closo‐undecaborate A 2[B 11H 11] (A = NBzlEt 3) can be halogenated with excess N‐chlorosuccine imide, bromine or iodine, respectively, to give the perhalo‐ closo‐undecaborates A 2[B 11Hal 11] (Hal = Cl, Br, I). The chlorination in the 11 : 1 ratio of the reagents yields A 2[B 11HCl 10], whose subsequent iodination makes A 2[B 11Cl 10I] available. The three type [B 11Hal 11] 2– anions show only one and the two type [B 11Cl 10X] 2– anions (X = H, I) only two 11B NMR peaks in the ratio 10 : 1, thus exhibiting the same degenerate rearrangement of the octadecahedral B 11 skeleton as is well‐known for [B 11H 11] 2–. The crystal structure analysis of A 2[B 11Br 11] and A 2[B 11I 11] reveals a rigid octadecahedral skeleton in the solid state, up to 330 K, whose B–B bond lengths deviate more or less from the idealized C2v gas phase structure, but are in good accordance with the distances of A 2[B 11H 11]. Electrochemical experiments elucidate the mechanism of the known oxidation of [B 11H 11] 2– to give [B 22H 22] 2–: A first one‐electron transfer is followed by the dimerization of the [B 11H 11] – monoanion, whereas neutral B 11H 11, a presumably most reactive species, does not play a role as an intermediate. The electrochemical oxidation of [B 11Hal 11] 2– anions also starts with a one‐electron transfer, which is perfectly reversible only in the case of Hal = Br. There is no electrochemical indication for the formation of [B 22Hal 22] 2–. The neutral species B 11Hal 11 should be a short‐lived, very reactive species. 相似文献
2.
The deprotonation of the nido‐anion [B 11H 14] – by two equivalents of Li tBu yields the anion [B 11H 12] 3–. Three observed 11B NMR shifts of this anion in the ratio 1 : 5 : 5 are in agreement with shifts calculated by the GIAO method on the basis of the ab initio computed geometry. The deprotonation can be reversed, giving back [B 11H 14] – via [B 11H 13] 2–. The thermolysis of [Li(thp) x] 3[B 11H 12] in thp at 80 °C leads to the closo‐borate [Li(thp) 3] 2[B 11H 11] under elimination of LiH. Anhydrous air transforms [B 11H 12] 3– into the known oxa‐ nido‐dodecaborate [OB 11H 12] –. The rhoda‐ closo‐dodecaborate [L 2RhB 11H 11] 3– is formed from [B 11H 12] 3– and RhL 3Cl (L = PPh 3). 相似文献
3.
closo-Undecaborates were synthesized by the deprotonation of B 11H 13(SMe 2) with Li tBu in thp or K[BHEt 3] in thf, [Li(thp) 3] 2[B 11H 11] and K 2[B 11H 11] being obtained in 83 and 93% yield, respectively. K 2[B 11H 11] can be transformed into A 2[B 11H 11] with the corresponding ammonium chlorides in aqueous solution (A = [NMe 3Ph], [NBzlEt 3], [N(PPh 3) 2]). The crystal structure analysis of [Li(thp) 3] 2[B 11H 11] (space group P2 1/ c) reveals a rather distorted octadecahedron for the [B 11H 11] 2– anion, whereas the corresponding octadecahedron in [NBzlEt 3] 2[B 11H 11] (space group P2 12 12 1) exhibits a structure close to C2v symmetry, expected for the free anion. The protonation of [B 11H 11] 2– at low temperature gives [B 11H 12] –, whose structure could be elucidated by NMR methods; it is formed, apparently, by the opening of the B1–B4 edge of [B 11H 11] 2– in the course of its known degenerate skeletal rearrangement, followed by the protonation of the B2–B4 edge. The reaction of [B 11H 12] – with a second molecule of the acid HX (X = CF 3COO) gives nido-[B 11H 13X] –. The addition of BH 3 to [B 11H 11] 2– yields closo-[B 12H 12] 2– under loss of H 2. Two [B 11H 11] 2– units are fused by the aid of FeCl 3, with the known anion [B 22H 22] 2– as the product, whose 11B-NMR signals could completely be assigned on the basis of Cs symmetry. The compound [NBzlEt 3][N(PPh 3) 2][B 22H 22] crystallizes in the space group Pna2 1. 相似文献
4.
The closo‐dodecaborate [B 12H 12] 2? is degraded at room temperature by oxygen in an acidic aqueous solution in the course of several weeks to give B(OH) 3. The degradation is induced by Ag 2+ ions, generated from Ag + by the action of H 2S 2O 8. Oxa‐ nido‐dodecaborate(1?) is an intermediate anion, that can be separated from the reaction mixture as [NBzlEt 3][OB 11H 12] after five days in a yield of 18 %. The action of FeCl 3 on the closo‐undecaborate [B 11H 11] 2? in an aqueous solution gives either [B 22H 22] 2? (by fusion) or nido‐B 11H 13(OH) ? (by protonation and hydration), depending on the concentration of FeCl 3. In acetonitrile, however, [B 11H 11] 2? is transformed into [OB 11H 12] ? by Fe 3+ and oxygen. The radical anions [B 12H 12] ˙ ? and [B 11H 11] ˙ ? are assumed to be the primary products of the oxidation with the one‐electron oxidants Ag 2+ and Fe 3+, respectively. These radical anions are subsequently transformed into [OB 11H 12] ? by oxygen. The crystal structure analysis shows that the structure of [OB 11H 12] ? is derived from the hypothetical closo‐oxaborane OB 12H 12 by removal of the B3 vertex, leaving a non‐planar pentagonal aperture with a three‐coordinate O vertex, as predicted by NMR spectra and theory. 相似文献
5.
A [H 3Ag I(H 2O)PW 11O 39] 3?-TiO 2/ITO electrode was fabricated by immobilizing a molecular polyoxometalate-based water oxidation catalyst, [H 3Ag I(H 2O)PW 11O 39] 3? (AgPW 11), on a TiO 2 electrode. The resulting electrode was characterized by X-ray powder diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Linear sweep voltammetry, chronoamperometry, and electrochemical impedance measurements were performed in aqueous Na 2SO 4 solution (0.1 mol L ?1). We found that a higher applied voltage led to better catalytic performance by AgPW 11. The AgPW 11-TiO 2/ITO electrode gave currents respectively 10 and 2.5 times as high as those of the TiO 2/ITO and AgNO 3-TiO 2/ITO electrodes at an applied voltage of 1.5 V vs Ag/AgCl. This result was attributed to the lower charge transfer resistance at the electrode-electrolyte interface for the AgPW 11-TiO 2/ITO electrode. Under illumination, the photocurrent was not obviously enhanced although the total anode current increased. The AgPW 11-TiO 2/ITO electrode was relatively stable. Cyclic voltammetry of AgPW 11 was performed in phosphate buffer solution (0.1 mol L ?1). We found that oxidation of AgPW 11 was a quasi-reversible process related to one-electron and one-proton transfer. We deduced that disproportionation of the oxidized [H 2Ag II(H 2O)PW 11O 39] 3? might have occurred and the resulting [H 3Ag IIIOPW 11O 39] 3? oxidized water to O 2. 相似文献
6.
The oxidation of 1,2-C2B10H12 (1) with 100% nitric acid was studied in two solvents (CH2C12 and CCl4). Under the action of superacid (CF3SO3H), the compound 9-HO-1,2-C2B10H11 (2) gives the onium cation 9-H2O+-1,2-C2B10H11 involved in the salt [9-H2O+-1,2-C2B10Hn]-CF3SO3?, as demonstrated by uB NMR spectroscopy. The experimental and simulated uB NMR spectra of the cation 9-H2O+-1,2-C2B10H11 are in satisfactory agreement with each other. In the presence of a base, compound 2 is transferred from an ethereal solution to an aqueous alkaline solution giving the anion 9-O?- 1,2-C2B10H11. The structure of compound 2 was confirmed by 1H, 11B, 11B1H, 11B-11B COSY NMR spectroscopy, IR spectroscopy, and gas chromatography mass spectrometry and was additionally established by X-ray diffraction. 相似文献
7.
The catalytic hydrogenation in acidic solution (pH ~ 2) of the title compound 1 In order to represent this and the related compounds by meaningful abbreviations, we shall adopt the numerotation system proposed in the literature [8] [12]. The complete abbreviation of the title compound is [Ni(5, 7, 7, 12, 14, 14-Me6-[14]-4, 11-diene-1, 4, 8, 11-N4)]2+. As in the present work the 14-membered ring system with six methyl groups remains unchanged, we shall use [Ni(4, 11-dieneN4)]2+ and [Ni(4, 11-aneN4)]2+ and [Ni(4, 11-aneN4)]2+ for the complex with the unsaturated and saturated ligand, respectively. [Ni(4, 11-dieneN 4)] 2+ (I) has been studied. The reaction yields only C- meso- 5, 7, 7, 12, 14, 14-hexa-methyl-1, 4, 8, 11-tetraaza-cyclotetradecane-nickel (II) (C- meso-[Ni(4, 11-aneN 4)] 2+), when meso-[Ni(4, 11-dieneN 4)] 2+ is the starting material. Rac-[Ni(4, 11-dieneN 4)] 2+ yields the unstable α-C- rac-[Ni(4, 11-aneN 4)] 2+. When optically active [Ni(4, 11-dieneN 4)] 2+ is reduced, optically active α-[Ni(4, 11-aneN 4)] 2+ is obtained, which in neutral or basic solution shows mutarotation due to conversion into optically active β-[Ni(4, 11-aneN 4)] 2+ no racemization is observed. Reaction with cyanide ions yields the optically active free tetramine ligand. The reaction mechanism of this asymmetric synthesis is discussed. 相似文献
8.
Superelectrophilic monoanions [B 12(BO) 11] − and [B 12(OBO) 11] −, generated from stable dianions [B 12(BO) 12] 2− and [B 12(OBO) 12] 2−, show great potential for binding with noble gases (Ngs). The binding energies, quantum theory of atoms in molecules (QTAIM), natural population analysis (NPA), energy decomposition analysis (EDA), and electron localization function (ELF) were carried out to understand the B−Ng bond in [B 12(BO) 11Ng] − and [B 12(OBO) 11Ng] −. The calculated results reveal that heavier noble gases (Ar, Kr, and Xe) bind covalently with both [B 12(BO) 11] − and [B 12(OBO) 11] − with large binding energies, making them potentially feasible to be synthesized. Only [B 12(OBO) 11] − could form a covalent bond with helium or neon but the small binding energy of [B 12(OBO) 11He] − may pose a challenge for its experimental detection. 相似文献
9.
The addition of neutral (L = py, NEt 3, NHEt 2, NH 2tBu) and anionic Lewis bases (X ‐ = OH ‐, Br ‐, N 3‐, Me ‐, NHBu ‐, NH tBu ‐, [FeCp(CO) 2] ‐) to aza‐ closo‐dodecaboranes RNB 11H 11 ( 1 ) or to derivatives thereof with boron bound non‐hydrogen ligands yields nido‐clusters RNB 11H 11L or [RNB 11H 11X] ‐ or derivatives thereof, respectively, the non‐planar pentagonal aperture N—B4—B9—B8—B5 of which hosts a B8—B9 hydrogen bridge. The base is either bound to B8 ( 3 )or B4 ( 5 )or B2( 7 ). The structures of these adducts are concluded from 1H and 11B NMR including 2D‐NMR spectra, and in the case of MeNB 11H 11(NHEt 2) (type 3 ) also by a crystal structure analysis. With two of the adducts MeNB 11H 11L (L = py, NHEt 2), isomers of the type 3 , 5 , and 7 , and with two of the adducts, MeNB 11H 11(NH 2tBu) and {MeNB 11H 11[FeCp(CO) 2]} ‐, isomers of the type 3 and 7 could be identified. The position of boron‐bound ligands during the addition of bases to 1 shows, that only vertices of the ortho‐belt of 1 are involved in the opening process. A mechanism is made plausible that starts by the attack of the base at B2 of 1 and opening of the N‐B2 bond, denoted as a [3c, 1c]‐collocation, to give 2 with an endo‐H atom, whose migration into an adjacent bridge position and opening of a second B—N bond, denoted as a [3c, 2c]‐translocation, gives 3 ; this isomer can be transformed into 7 by a sequence of [3c, 2c]‐translocations via the isomers 4 , 5 , and 6 . The chiral type 3 species MeNB 11H 11L with L = NHEt 2, NH 2tBu undergo a rapid enantiomerization, for whose mechanism the exchange of the bridging and the amine‐H atom has been made plausible. 相似文献
10.
High-voltage alkali metal-ion batteries (AMIBs) require a non-hazardous, low-cost, and highly stable electrolyte with a large operating potential and rapid ion conductivity. Here, we have reported a halogen-free high-voltage electrolyte based on SiB 11(BO) 12−. Because of the weak π-orbital interaction of −BO as well as the mixed covalent and ionic interaction between SiB 11-cage and −BO ligand, SiB 11(BO) 12− has colossal stability. SiB 11(BO) 12− possesses extremely high vertical detachment energy (9.95 eV), anodic voltage limit (∼10.05 V), and electrochemical stability window (∼9.95 V). Furthermore, SiB 11(BO) 12− is thermodynamically stable at high temperatures, and its large size allows for faster cation movement. The alkali salts MSiB 11(BO) 12 (M=Li, Na, and K) are easily dissociated into ionic components. Electrolytes based on SiB 11(BO) 12− greatly outperform commercial electrolytes. In short, SiB 11(BO) 12−-based compound is demonstrated to be a high-voltage electrolyte for AMIBs. 相似文献
11.
The 14N/p, / 11C-reaction was studied in different N 2/H 2-mixtures. The products are [ 11C]-CO 2, [ 11C]-CO and [ 11C]-CH 4. The yield ratio may be controlled by varying the bombardment conditions. High pressure, high H 2-content, high beam current and high proton energy shift the ratio towards [ 11C]-CH 4. Lower beam current and lower proton energy increase the yield of [ 11C]-CO 2. The production of [ 11C]-CO is constant over a wide range of conditions /about 10%/. For the production of [ 11C]-CH 4 in good yield a target gas holder for high pressures has been developed. Details are given in Fig. 7. This target gas holder was filled with 5% H 2 in N 2 at 3×10 6 Pa. Proton irradiation of the mixture gives a typical yield of [ 11C]-CH 4 of 400–500 mCi at a beam current of 15–20 A within 20 min. Only traces of other 11C-labelled compounds could be detected under these conditions. 相似文献
12.
Stoichiometric reduction of Os 3CO) 12 and Ru 3(CO) 12 with K and Ca, respectively; yields the two new cluster dianions [Os 3(CO) 11] 2? and [Ru 3(CO) 11] 2? which have been isolated and characterized. Temperature-dependent 13C NMR spectra for [Os 3(CO) 11] 2? and infrared spectra of [Os 3(CO) 11] 2? and [Ru 3(CO) 11] 2? suggest a similar structure for these dianions in which there is a single edge-bridging carbonyl. 相似文献
13.
Electrophilic deuteration of closo-[1-CB 11H 12] − in the DCl/D 2O system confirmed the expected order of reactivity on individual skeletal atoms, decreasing in the series B(12) > B(7–11) > B(2–6) > C(1). In contrast, electrophilic B-substitution of closo-[1-CB 11H 12] − with H 2NOSO 3H is consistent with the preference of the B(7)-substitution to suggest a different mechanism for almost exclusive formation of 7-H 3N- closo-1-CB 11H 11. 7-Me 3N- closo-1-CB 11H 11 was isolated along with the remaining 2- and 12-Me 3N-1-CB 11H 11 isomers as side products of the thermal decomposition of [BH 2(NMe 3) 2] +[ nido-7-CB 10H 13] − at 270°C, which is inconsistent with a specific insertion of the BNMe 3 fragment into the open face of nido-[7-CB 10H 13] −. Nevertheless, clean 10B-insertion was observed in the reactions of Et 3N 10BH 3 with both nido-[7-CB 10H 13] − and 7-Me 3N- nido-7-CB 10H 12 to give respectively closo-[1-CB 11H 12] − and [1-Me 2N-1-CB 11H 11] − labelled by 10B exclusively at the B(2) site. Cage rearrangement was observed, however, in the reaction of 7-Me 3N-8-PhCH 2- nido-7-CB 10H 11 with Et 3NBH 3 under similar conditions to produce only the 1-Me 3N-7-PhCH 2-1-CB 11H 10 closo-isomer. 相似文献
14.
Measurements of core and valence electronic states of single crystals of the rare earth transition metal Zintl phases Yb 14MnSb 11 and Yb 14ZnSb 11 were performed using the X-ray photoelectron spectroscopy station of Beamline 7 at the Advanced Light Source. Sample surfaces of Yb 14MnSb 11 and Yb 14ZnSb 11 were measured as received, after Ar + ion bombardment, and after cleaving in situ. The single crystal structure of Yb 14ZnSb 11 is also reported. Both compounds are air-sensitive and show Yb 3+ due to surface oxidation. In the case of Yb 14MnSb 11, there is no evidence for Yb 3+ that would be intrinsic to the sample, consistent with previously reported X-ray magnetic circular dichroism studies. Detailed analyses of the Yb 14ZnSb 11 surfaces reveal a significant contribution of both Yb 3+ and Yb 2+ 4 f states in the valence band region. This result is predicted for the Zn analog by Zintl counting rules and support the mixed valency of Yb for Yb 14ZnSb 11. Further detailed analysis of the core and valence band structure of both Yb 14MnSb 11 and Yb 14ZnSb 11 is presented. 相似文献
15.
Aimed at substantiating the formation mechanism of the heteropolytungstates of the 2:11 type: [H hM m+O 6X x+O 11O 30] (14-m-x-h)-, via complexes of the 1:11 type, attempts were made to introduce a second heteroatozn in the latter. A new, simple synthesis method was established for the 2:11 heteropolytungstates (X = P, Si; M = Ni), starting with complexes of the type [X x+W 11O 39] 12-x (X = P, Si) and by using an ion exchange method (Amberlite I.R. 120. Ni 2+, K +). The correctness of the supposed reaction way was demonstrated and at the same time, the close structural relationship between the hetero-polytung?states of the type 1:11 and 2:11 -was pointed out. 相似文献
16.
The Stille cross-coupling reaction of [1- 11C]acetyl chloride with tributylphenylstannane leading to [ carbonyl- 11C]acetophenone was studied with the goal of developing a new 11C-labeling method for positron emission tomography tracer synthesis. The coupled product [ carbonyl- 11C]acetophenone was synthesized using the Pd 2(dba) 3/P(MeNCH 2CH 2) 3N·HCl system with a 60-61% radiochemical conversion from [1- 11C]acetyl chloride (decay-corrected, n = 3). 相似文献
17.
DFT‐calculations of the geometries of the closo‐anion [B 11H 11] 2– in its ground state and in the transition state of its skeletal rearrangement and of the protonated species [B 11H 12] – in its ground state were performed at the B3LYP/6‐31++G(d,p) level. The corresponding NMR shifts were computed on the basis of the optimized geometry by the GIAO method at the same level. Calculated and observed NMR data are in good agreement and thus prove the structure of [B 11H 12] –, previously deduced from 2 D‐NMR spectra. The addition of water, ethanol, and pyridine to [B 11H 12] – at low temperature gave the nido‐species [B 11H 13(OH)] –, [B 11H 13(OEt)] –, and [B 11H 12(py)] –, respectively. The structures of these anions were investigated by NMR methods and the last two of them by crystal structure analyses of appropriate salts. The course of the addition reactions can be rationalized on the basis of the structurally characterized reaction components. 相似文献
18.
The AlX 3-catalyzed (X = Cl, Br, and I) halogenation of arachno-4,5-C 2B 7H 13 with anhydrous hydrogen halides produces a series of 6-substituted derivatives, 6-X-4,5-C 2B 7H 12. The same compounds along with 6,8-I 2-4,5-C 2B 7H 11 are obtained in non-catalyzed reactions with elemental halogens. The electrophile-induced nucleophilic substitution concept (EINS) of the substitution with hydrogen halides is suggested. The constitution of all compounds isolated was unambiguously determined via 1H, 13C, 11B, and two-dimensional (2-D) 11B- 11B NMR spectra. 相似文献
19.
Geometry, vibrational and NMR spectra of the icosahedral aza- closo-dodecaborane MeNB 11H 11 are calculated by ab initio methods. The results are compared with experimental data. They are in accord with local C5v symmetry of the cluster unit and local C3v symmetry of the methyl group. The boron atoms B7–B11 are coupled to B12 by the small constant 1J ( 11B, 11B) = 12 Hz. 相似文献
20.
Aggregated β‐amyloid (Aβ) is widely considered as a key factor in triggering progressive loss of neuronal function in Alzheimer's disease (AD), so targeting and inhibiting Aβ aggregation has been broadly recognized as an efficient therapeutic strategy for curing AD. Herein, we designed and prepared an organic platinum‐substituted polyoxometalate, (Me 4N) 3[PW 11O 40(SiC 3H 6NH 2) 2PtCl 2] (abbreviated as Pt II‐PW 11) for inhibiting Aβ 42 aggregation. The mechanism of inhibition on Aβ 42 aggregation by Pt II‐PW 11 was attributed to the multiple interactions of Pt II‐PW 11 with Aβ 42 including coordination interaction of Pt 2+ in Pt II‐PW 11 with amino group in Aβ 42, electrostatic attraction, hydrogen bonding and van der Waals force. In cell‐based assay, Pt II‐PW 11 displayed remarkable neuroprotective effect for Aβ 42 aggregation‐induced cytotoxicity, leading to increase of cell viability from 49 % to 67 % at a dosage of 8 μm . More importantly, the Pt II‐PW 11 greatly reduced Aβ deposition and rescued memory loss in APP/PS1 transgenic AD model mice without noticeable cytotoxicity, demonstrating its potential as drugs for AD treatment. 相似文献
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