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51.
Production and Decomposition of (NH4)[BF4] and H3N‐BF3 (NH4)[BF4] is produced as single crystals during the reaction of elemental boron and NH4HF2 (B : NH4HF2 = 1 : 2) and NH4F (B : NH4F = 1 : 4), respectively, in sealed copper ampoules at 300 °C. The crystal structure (baryte type, orthorhombic, Pnma, Z = 4) was redetermined at ambient temperature (a = 909.73(18), b = 569.77(10), c = 729.47(11) pm, Rall = 0.0361) and at 140 K (a = 887.3(2), b = 574.59(12), c = 717.10(12) pm, Rall = 0.0321). Isolated (NH4)+ and [BF4]— tetrahedra are the important building units. The thermal behaviour of (NH4)[BF4] was investigated under inert (Ar, N2) and reactive conditions (NH3) with the aid of DTA/TG and DSC measurements and with in‐situ X‐ray powder diffraction as well. Finally, (NH4)[BF4] is decomposed yielding NH3 and BF3, BN is not produced under the current conditions. Colourless single crystals of H3N‐BF3 were prepared directly from the components NH3 and BF3. The crystal structure was determined anew at 293 and 170 K (orthorhombic, Pbca, Z = 8, a = 815.12(10), b = 805.91(14), c = 929.03(12) pm, Rall = 0.0367; a = 807.26(13), b = 800.48(10), c = 924.31(11) pm, Rall = 0.0292, T = 170 K). The crystal structure contains isolated molecules H3N‐BF3 in staggered conformation with a B‐N distance of 158 pm. The thermal behaviour of H3N‐BF3 was studied likewise. 相似文献
52.
Daewon Hong Patrick J. Carroll Larry G. Sneddon 《Journal of organometallic chemistry》2003,680(1-2):61-65
The new 11-vertex nido-diphosphaborane, 7,9-Ph2-nido-7,9-P2B9H9, has been synthesized by the reaction of Me4N+[nido-B9H12−] with PhPCl2 in the presence of NaH. A single crystal X-ray diffraction determination and DFT/GIAO/NMR methods have both established that the compound has an open cage structure containing the phosphorus atoms in non-adjacent positions on the open face. 相似文献
53.
Detlef Gabel Claudia Bauer Mohamed E. El-Zaria Afaf R. Genady Udo Drfler 《Journal of organometallic chemistry》2003,680(1-2):23-26
The preparation and properties of the R1R2NH---B8H11NHR cluster are described. The cluster is stable to aqueous solutions and can be made water-soluble by the introduction of a few hydrophilic groups. This makes the cluster a good candidate as the boron moiety in compounds for boron neutron capture therapy. The chemistry of the cluster preparation, the stability of the cluster, and conditions for reactions of the organic moieties are reviewed. Pyridine derivatives of the cluster show electronic interaction between the cluster and the pyridine. 相似文献
54.
Harald Hillebrecht Natascha Vojteer Vanessa Sagawe Kathrin Hofmann Barbara Albert 《无机化学与普通化学杂志》2019,645(3):362-369
Transparent and nearly colorless single crystals of r‐LiB13C2 were obtained by reaction of boron with Li2CO3 in a Cu melt at 1250–1300 °C. The structure analysis [R3 m, a = 5.6535(1), c = 12.5320(2) Å, 421 independent reflections, 22 parameters, R1 = 0.034, wR2 = 0.093] revealed a crystal structure that can be described as a filling variant of rhombohedral B13C2. Li+ is located in a void above or below the linear CBC unit. The site occupation is close to 50 % resulting in an electron‐precise composition according to Wade's rules if a positive charge is given to the CBC entity: Li+(B12)2–(CBC)+. The displacement parameters of the CBC unit indicate disorder in the [001] direction, that relates to the short Li–C distance and the partial occupation of the Li+ site. The composition is confirmed by EELS measurements of single crystals. Band gap calculations give a value of 2.94 eV, which is in agreement to the crystals being colorless. The evaluation of the electron density by application of the QTAIM formalism as proposed by Bader modifies the assignment pictured above according to Wade's rules. In agreement to the electronegativities the carbon atoms carry a negative charge (–2.31/–2.42) and the effective charges are: Li+0.81(B12)+2.02(CBC)–2.83. 相似文献
55.
Au/TiO2 nanorod composites with different ratios of [TiO2]:[Au] have been prepared by chemically reducing AuCl4‐ on the positively charged TiO2 nanorods surface and used to modify boron‐doped diamond (BDD) electrodes. The electrochemical behaviors of catechol on the bare and different Au/TiO2 nanorod composites‐modified BDD electrodes are studied. The cyclic voltammetric results indicate that these different Au/TiO2 nanorod composites‐modified BDD electrodes can enhance the electrocatalytic activity toward catechol detection, as compared with the bare BDD electrode. Among these different conditions, the Au/TiO2‐BDD3 electrode (the ratio of [TiO2]:[Au] is 27:1) is the most choice for catechol detection. The electrochemical response dependences of the Au/TiO2‐BDD3 electrode on pH of solution and the applied potential are studied. The detection limit of catechol is found to be about 1.4 × 10‐6 M in a linear range from 5 × 10‐6 M to 200 × 10‐6 M on the Au/TiO2‐BDD3 electrode. 相似文献
56.
Rb2Co3(H2O)2[B4P6O24(OH)2]: A Borophosphate with ‐Tetrahedral Anionic Partial Structure and Trimers of Octahedra (Co O12(H2O)2) Rb2Co3(H2O)2[B4P6O24(OH)2] is formed under mild hydrothermal conditions (T = 165 °C) from mixtures of RbOH(aq), CoCl2, H3BO3, and H3PO4 (molar ratio 1 : 1 : 1 : 2). The crystal structure (orthorhombic system) was solved by X‐ray single crystal methods (space group Pbca, No. 61; R‐values (all data): R1 = 0.0699, wR2 = 0.0878): a = 950.1(1) pm, b = 1227.2(2) pm, c = 2007.4(2) pm; Z = 4. The anionic partial structure consists of tetrahedral [B4P6O24(OH)28–] layers, which contain three‐ and nine‐membered rings. CoII is octahedrally coordinated by oxygen and oxygen and H2O ligands, respectively (coordination octahedra CoO6 and CoO4(H2O)2). Three adjacent coordination octahedra are condensed via common edges to form trimeric units (CoO12(H2O)2). The oxidation state +2 of cobalt was confirmed by magnetic measurements. The octahedral trimers are quasi‐isolated. No long‐range magnetic ordering occurs down to 2 K. Rb+ is disordered over three crystallographically independent sites within channels of the structure running parallel [010]; the coordination sphere of Rb+ is formed by nine oxygen species of the tetrahedral layers, one OH group and one H2O molecule. 相似文献
57.
The oxonium derivative P(C6H5)4[2-B10H9O(CH2)4] (1) has been prepared from [B10H10]2− by a solvent-addition reaction route, promoted by Et2O · BF3. Its structure has been confirmed by single crystal X-ray analysis. 1 is assumed to be a useful synthon for the derivative chemistry of [B10H10]2−. As an illustration, ring-opening reaction occurred in presence of the strong nucleophilic agent OH−, giving the monoanionic derivative [P(C6H5)4]2[2-B10H9O(CH2)4OH] (2). 相似文献
58.
Densification of boron carbide during sintering may be improved by a two-stage process, namely heating to 2000°C under vacuum and sintering at 2190°C under argon. This sintering regime allows achieving a relative density of the ceramic bodies fabricated from a fine powder higher than 95%. The nitrogen treatment of the boron carbide phase at 1900°C leads to the formation of the BN phase and precipitation of graphite. Vacuum treatment of these samples at 2000°C leads to decomposition of the boron nitride phase. The liberated free boron may again react with graphite to form in situ boron carbide particles. The experimental investigations of the sintering behavior of the boron carbide phase under various atmospheres supported the thermodynamic predictions regarding the phase transformation. No evidence, however, was found for enhanced sintering under a nitrogen atmosphere. 相似文献
59.
Carlos A.M Fraga Lis Helena P Teixeira Carla Maria de S Menezes Maria da Conceição K.V Ramos Eliezer J Barreiro 《Tetrahedron》2004,60(12):2745-2755
Reduction of 2-allyl-2-carboalkoxycyclohexanones (3d-f), 2-propyl-2-carboethoxycyclohexanone (3g) and 2-benzyl-2-carboethoxycyclohexanone (3h) with boron hydrides in the presence and absence of several chelating agents were studied. Molecular modeling studies using semiempirical PM3 method were performed in order to find a suitable explanation of the diastereoselection of ketone carbonyl faces during the reductive process, which yielded trans-2-allyl-2-carboethoxycyclohexanol (6e) and cis-2-allyl-2-carboethoxycyclohexanol (7e) in good diastereomeric excess by using inexpensive sodium and tetrabutylammonium borohydrides. 相似文献
60.
Charlotta Naeslund 《Tetrahedron》2005,61(5):1181-1186
The enantiomers of the highly lipophilic α-amino acid m-carboranyl-alanine [3-(1,7-dicarba-closo-dodecaborane(12)-1-yl)-2-aminopropanoic acid], a carborane containing analogue of phenylalanine, have been synthesised via hydroxyamination of the N-acyl derivative formed from 3-(m-carboranyl)propionic acid [3-(1,7-dicarba-closo-dodeca-borane(12)-1-yl)-2-propanoic acid] and Oppolzer's camphor sultam. The enantiomeric excess of both enantiomers of the amino acid was >98%. (S)-Configuration was assigned to the (+)-enantiomer (CH3OH, 589 nm). 相似文献