Vanadium(III) chloride describes theinorganic compound with theformula VCl3 and its hydrates. It forms a purple anhydrous form and a green hexahydrate [VCl2(H2O)4]Cl·2H2O. Thesehygroscopic salts are common precursors to other vanadium(III) complexes and is used as a mildreducing agent.[5]
VCl3 has the common layeredBiI3 structure, a motif that features hexagonally closest-packed chloride framework with vanadium ions occupying the octahedral holes.[6]VBr3 andVI3 adopt the same structure, butVF3 features a structure more closely related toReO3.[3] The V3+cation has ad2 electronic configuration with two unpaired electrons, making the compoundparamagnetic.[7] VCl3 is aMott insulator and undergoes anantiferromagnetic transition at low temperatures.[6][8]
Solid hexahydrate, [VCl2(H2O)4]Cl·2H2O, has amonoclinic crystal structure and consists of slightly distorted octahedraltrans-[VCl2(H2O)4]+ centers as well as chloride and two molecules ofwater of crystallization.[9][10] The hexahydrate phase loses twowater of crystallization to form the tetrahydrate if heated to 90 °C in a stream ofhydrogen chloride gas.[1]
Plan view of a single layer in the crystal structure of vanadium(III) chloride
Layer stacking in the crystal structure of vanadium(III) chloride
Unit cell of hexahydrate, featuring [VCl2(H2O)4]+ centres
Solutions of vanadium(III) chloride insulfuric acid andhydrochloric acid are used as electrolytes invanadium redox batteries.[11] It is also used as a mildLewis acid in organic synthesis. One example of such is its use as a catalyst in the cleavage of theacetonide group.[12] Another example of the use of VCl3 as a reducing agent is shown in the determination ofnitrate andnitrite concentration in water, where VCl3 reduces nitrate to nitrite. This method is a safer alternative to the cadmium column method.[13]
VCl3 is prepared by heatingVCl4 at 160–170 °C under a flowing stream of inert gas, which sweeps out theCl2. The bright red liquid converts to a purple solid.[14]
When dissolved in water, the compound forms the greenhydrate:[15]
VCl3 + 4 H2O → [VCl2(H2O)4]+ + Cl−
Heating of VCl3 decomposes with volatilization of VCl4, leaving VCl2 above 350 °C.[2][15] Upon heating under H2 at 675 °C (but less than 700 °C), VCl3 reduces to greenish VCl2.
The heating of the hexahydrate does not give the anhydrous form, instead undergoes partial hydrolysis and formsvanadium oxydichloride at 160 °C. In an inert atmosphere, it forms a trihydrate at 130 °C and at higher temperatures, it forms vanadium oxychloride.[17]
Vanadium trichloride catalyses thepinacol coupling reaction of benzaldehyde (PhCHO) to 1,2-diphenyl-1,2-ethanediol by various reducing metals such as zinc:[18]
VCl3 forms colorful adducts and derivatives with a broad scale of ligands. VCl3 dissolves in water to give theaquo complexes. From these solutions, the hexahydrate [VCl2(H2O)4]Cl.2H2O crystallizes. In other words, two of the water molecules are not bound to the vanadium, whose structure resembles the corresponding Fe(III) derivative. Removal of the two bound chloride ligands gives the green hexaaquo complex [V(H2O)6]3+.[9][19]
Structure of VCl3(thf)3.[20]A solution of vanadium(III) chloride
Withtetrahydrofuran, VCl3 forms the red/pink complex VCl3(THF)3,[21] and the red complex [VCl3(THF)2]2.[22] Reduction of VCl3(THF)3 gives [(V(THF)3)2Cl3]2[Zn2Cl6], Caulton's reagent".[23]
Vanadium(III) chloride reacts withacetonitrile to give the green adduct VCl3(MeCN)3. When treated with KCN, VCl3 converts to [V(CN)7]4− (early metals commonly adopt coordination numbers greater than 6 with compact ligands). Complementarily, larger metals can form complexes with rather bulky ligands. This aspect is illustrated by the isolation of VCl3(NMe3)2, containing two bulky NMe3 ligands. Vanadium(III) chloride is able to form complexes with other adducts, such aspyridine ortriphenylphosphine oxide.[19]
^abcSally M. Horner; S. Y. Tyree (1964). "Chloro-Aquo Complexes of Vanadium(III)".Inorganic Chemistry.3 (8):1173–1176.doi:10.1021/ic50018a024.
^abYajima Akimasa; Matsuzaki Ryoko; Saeki Yuzo (1979). "The Thermal Decomposition of Vanadium(III) Chloride Oxide and Its Reaction with Oxygen".Bulletin of the Chemical Society of Japan.52 (11):3292–3295.doi:10.1246/bcsj.52.3292.
^abcdWilhelm Klemm; Ehrhard Krose (1947). "Die Kristallstrukturen von ScCl3, TiCl3 und VCl3" [The Crystal Structures of ScCl3, TiCl3 and VCl3].Zeitschrift für anorganische Chemie (in German).253 (3–4):218–225.doi:10.1002/zaac.19472530313.
^John Rumble (June 18, 2018).CRC Handbook of Chemistry and Physics (99 ed.). CRC Press. pp. 5–40.ISBN978-1-138-56163-2.
^Holleman, A. F.; Wiberg, E.Inorganic Chemistry Academic Press: San Diego, 2001.ISBN0-12-352651-5.
^abDonovan, William F.; Smith, Peter W. (1975). "Crystal and Molecular Structures of Aquahalogenovanadium(III) Complexes. Part I. X-Ray Crystal Structure oftrans-Tetrakisaquadibromo-Vanadium(III) Bromide Dihydrate and the Isomorphous Chloro- Compound".Journal of the Chemical Society, Dalton Transactions (10): 894.doi:10.1039/DT9750000894.
^Fiona H. Fry; Brenda Dougan; Nichola McCann; Anthony C. Willis; Christopher J. Ziegler; Nicola E. Brasch (2008). "Synthesis and X-ray structural characterization of tris(l-glycinato)vanadium(III) and trans-tetraquadichlorovanadium(III) chloride".Inorganica Chimica Acta.361 (8):2321–2326.doi:10.1016/j.ica.2007.11.025.
^Günter Bauer; Volker Güther; Hans Hess; Andreas Otto; Oskar Roidl; Heinz Roller; Siegfried Sattelberger; Sven Köther-Becker; Thomas Beyer (2017).Vanadium and Vanadium Compounds. Wiley-VCH Verlag GmbH & Co. KGaA. p. 16.doi:10.1002/14356007.a27_367.pub2.ISBN978-3-527-30385-4.
^Gowravaram Sabitha; G.S. Kiran Kumar Reddy; K. Bhaskar Reddy; N. Mallikarjuna Reddy; J.S. Yadav (2005). "Vanadium(III) chloride: A mild and efficient catalyst for the chemoselective deprotection of acetonides".Journal of Molecular Catalysis A: Chemical.238 (1–2):229–232.doi:10.1016/j.molcata.2005.05.028.
^Bernhard Schnetger; Carola Lehners (2014). "Determination of nitrate plus nitrite in small volume marine water samples using vanadium(III)chloride as a reduction agent".Marine Chemistry.160:91–98.Bibcode:2014MarCh.160...91S.doi:10.1016/j.marchem.2014.01.010.
^G. Brauer (1963). "Vanadium Oxydichloride". In G. Brauer (ed.).Handbook of Preparative Inorganic Chemistry, 2nd Ed. NY: Academic Press. p. 1263.
^Ray Colton; J. H. Canterford (1969).Halides of the first row transition metals. Wiley. p. 131.ISBN978-0-471-16625-2.
^Xu; Hirao, Toshikazu (2005). "Vanadium-Catalyzed Pinacol Coupling Reaction in Water".The Journal of Organic Chemistry.70 (21):8594–8596.doi:10.1021/jo051213f.PMID16209617.
^abD. Nicholls (1966). "The coordination chemistry of vanadium".Coordination Chemistry Reviews.1 (3):379–414.doi:10.1016/S0010-8545(00)80145-9.
^Albert Cotton, F.; Duraj, Stan A.; Powell, Gregory L.; Roth, Wieslaw J. (1986). "Comparative Structural Studies of the First Row Early Transition Metal(III) Chloride Tetrahydrofuran Solvates".Inorganica Chimica Acta.113: 81.doi:10.1016/S0020-1693(00)86863-2.
^Sobota, Piotr; Ejfler, Jolanta; Szafert, Sławomir; Szczegot, Krzysztof; Sawka-Dobrowolska, Wanda (1993). "New intermediates for the Synthesis of Olefin Polymerization Catalysts: The Complexes [M2(μ-Cl)2Cl4(THF)4] (M = Ti or V, THF = Tetrahydrofuran); Crystal Structures and Properties".Journal of the Chemical Society, Dalton Transactions (15):2353–2357.doi:10.1039/dt9930002353.
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