| 词条 | Niobium(V) chloride |
| 释义 |
| Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 431997260 | Name = Niobium(V) chloride | ImageFile = Niobium pentachloride solid.jpg | ImageName = Sample of niobium(V) chloride | ImageFile1 = Niobium-pentachloride-dimer-2D.png | ImageName2 = Niobium pentachloride liquid and vapor | IUPACName = Niobium(V) chloride Niobium pentachloride |Section1={{Chembox Identifiers | CASNo1_Ref = {{cascite|correct|chemspider}} | CASNo1 = 10026-12-7 | CASNo1_Comment = NbCl5 | CASNo2_Ref = {{cascite|changed|??}} | CASNo2 = 17499-28-4 | CASNo2_Comment = Nb2Cl10 | CASNo_Ref = {{cascite}} | UNII_Ref = {{fdacite|changed|FDA}} | UNII = 9S1BC7865F | EINECS = 233-059-8 | RTECS = QU0350000 | PubChem = 24818 | ChemSpiderID = 23203 | StdInChI=1S/5ClH.Nb/h5*1H;/q;;;;;+5/p-5 | StdInChIKey = YHBDIEWMOMLKOO-UHFFFAOYSA-I | SMILES = Cl[Nb](Cl)(Cl)(Cl)Cl | SMILES1 = Cl[Nb-]1(Cl)(Cl)(Cl)[Cl+][Nb-]([Cl+]1)(Cl)(Cl)(Cl)Cl | SMILES1_Comment = dimer |Section2={{Chembox Properties | Formula = NbCl5 | Appearance = yellow monoclinic crystals deliquescent | MolarMass = 270.17 g/mol | Density = 2.75 g/cm3 | Solubility = decomposes | SolubleOther = HCl, chloroform, CCl4 | MeltingPtC = 204.7 | BoilingPtC = 248.2 |Section4={{Chembox Thermochemistry | DeltaHf = -797.47 kJ/mol | Entropy = 214.05 J K−1 mol−1 |Section7={{Chembox Hazards | ExternalSDS = | FlashPt = Non-flammable | PEL = | GHSPictograms = {{GHS05}}{{GHS07}} | GHSSignalWord = Danger | HPhrases = {{H-phrases|302|312|314|332}} | PPhrases = {{P-phrases|260|261|264|270|271|280|301+312|301+330+331|302+352|303+361+353|304+312|304+340|305+351+338|310|312|321|322|330|363|405|501}} |Section8={{Chembox Related | OtherAnions = Niobium(V) fluoride Niobium(V) bromide Niobium(V) iodide | OtherCations = Vanadium(IV) chloride Tantalum(V) chloride | OtherFunction = Niobium(III) chloride Niobium(IV) chloride | OtherFunction_label = niobium chlorides }}Niobium(V) chloride, also known as niobium pentachloride, is a yellow crystalline solid. It hydrolyzes in air, and samples are often contaminated with small amounts of NbOCl3. It is often used as a precursor to other compounds of niobium. NbCl5 may be purified by sublimation.[1] Structure and propertiesNiobium(V) chloride forms chloro-bridged dimers in the solid state (see figure). Each niobium centre is six-coordinate, but the octahedral coordination is significantly distorted. The equatorial niobium–chlorine bond lengths are 225 pm (terminal) and 256 pm (bridging), whilst the axial niobium-chlorine bonds are 229.2 pm and are deflected inwards to form an angle of 83.7° with the equatorial plane of the molecule. The Nb–Cl–Nb angle at the bridge is 101.3°. The Nb–Nb distance is 398.8 pm, too long for any metal-metal interaction.[2] NbBr5, TaCl5 and TaBr5 are isostructural with NbCl5, but NbI5 and TaI5 have different structures. PreparationIndustrially, niobium pentachloride is obtained by direct chlorination of niobium metal at 300 to 350 °C:[3] 2 Nb + 5 Cl2 → 2 NbCl5 In the laboratory, niobium pentachloride is often prepared from Nb2O5, the main problem being incomplete reaction to give the oxyhalides. The conversion can be effected with thionyl chloride:[4] It also can be prepared by chlorination of niobium pentoxide in the presence of carbon at 300 °C. The products, however, contain small amounts of NbOCl3. {{clear|left}}UsesNiobium(V) chloride is the main precursor to the alkoxides of niobium, which find niche uses in sol-gel processing. It is also the precursor to many other laboratory reagents. In organic synthesis, NbCl5 is a specialized Lewis acid in activating alkenes for the carbonyl-ene reaction and the Diels-Alder reaction. Niobium chloride can also generate N-acyliminium compounds from certain pyrrolidines which are substrates for nucleophiles such as allyltrimethylsilane, indole, or the silyl enol ether of benzophenone.[5] References1. ^{{Cotton&Wilkinson4th}} 2. ^{{cite journal | author = Cotton, F.A., P. A. Kibala, M. Matusz and R. B. W. Sandor | year = 1991 | title = Structure of the Second Polymorph of Niobium Pentachloride | journal = Acta Crystallogr. C | volume = 47 | pages = 2435–2437 | doi = 10.1107/S0108270191000239 | issue = 11}} 3. ^{{cite encyclopedia|authors=Joachim Eckert, Hermann C. Starck|title=Niobium and Niobium Compounds|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry|year=2005|publisher=Wiley-VCH|place=Weinheim|doi=10.1002/14356007.a17_251}} 4. ^D. Brown "Niobium(V) Chloride and Hexachloroniobates(V)" Inorganic Syntheses, 1957 Volume 9, pp. 88–92.{{DOI|10.1002/9780470132401.ch24}} 5. ^{{cite journal | author1 = Andrade, C. K. Z. | author2 = Rocha, R. O. | author3 = Russowsky, D. | author4 = Godoy, M. N. | last-author-amp = yes | year = 2005 | title = Studies on the Niobium Pentachloride-Mediated Nucleophilic Additions to an Enantiopure Cyclic N-acyliminium Ion Derived from (S)-malic acid | journal = J. Braz. Chem. Soc. | volume = 16 | pages = 535–539 | url = http://jbcs.sbq.org.br/online/2005/vol16_n3B/06-144-04.pdf | doi = 10.1590/S0103-50532005000400007 | issue = 3b | deadurl = yes | archiveurl = https://web.archive.org/web/20071012041838/http://jbcs.sbq.org.br/online/2005/vol16_n3B/06-144-04.pdf | archivedate = 2007-10-12 | df = }} External links
3 : Niobium compounds|Chlorides|Metal halides |
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