Indium(III)_chloride

Indium(III) chloride

Indium(III) chloride

Chemical compound

Indium(III) chloride is the chemical compound with the formula InCl3 which forms a tetrahydrate. This salt is a white, flaky solid with applications in organic synthesis as a Lewis acid. It is also the most available soluble derivative of indium.[2] This is one of three known indium chlorides.

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Synthesis and structure

Being a relatively electropositive metal, indium reacts quickly with chlorine to give the trichloride. Indium trichloride is very soluble and deliquescent.[3] A synthesis has been reported using an electrochemical cell in a mixed methanol-benzene solution.[4]

Like AlCl3 and TlCl3, InCl3 crystallizes as a layered structure consisting of a close-packed chloride arrangement containing layers of octahedrally coordinated In(III) centers,[5] a structure akin to that seen in YCl3.[6] In contrast, GaCl3 crystallizes as dimers containing Ga2Cl6.[6] Molten InCl3 conducts electricity,[5] whereas AlCl3 does not as it converts to the molecular dimer, Al2Cl6.[7]

Reactions

InCl3 is a Lewis acid and forms complexes with donor ligands, L, InCl3L, InCl3L2, InCl3L3. For example, with the chloride ion it forms tetrahedral InCl4−, trigonal bipyramidal InCl52−, and octahedral InCl63−.[5]

In diethyl ether solution, InCl3 reacts with lithium hydride, LiH, to form . This unstable compound decomposes below 0 °C,[8] and is reacted in situ in organic synthesis as a reducing agent[9] and to prepare tertiary amine and phosphine complexes of InH3.[10]

Trimethylindium, InMe3, can be produced by reacting InCl3 in diethyl ether solution either with the Grignard reagent or methyllithium, LiMe. Triethylindium can be prepared in a similar fashion but with the grignard reagent EtMgBr.[11]

InCl3 reacts with indium metal at high temperature to form the lower valent indium chlorides In5Cl9, In2Cl3 and InCl.[5]

Catalyst in chemistry

Indium chloride is a Lewis acid catalyst in organic reactions such as Friedel-Crafts acylations and Diels-Alder reactions. As an example of the latter,[12] the reaction proceeds at room temperature, with 1 mole% catalyst loading in an acetonitrile-water solvent mixture. The first step is a Knoevenagel condensation between the barbituric acid and the aldehyde; the second step is a reverse electron-demand Diels-Alder reaction, which is a multicomponent reaction of N,N'-dimethyl-barbituric acid, benzaldehyde and ethyl vinyl ether. With the catalyst, the reported chemical yield is 90% and the percentage trans isomer is 70%. Without the catalyst added, the yield drops to 65% with 50% trans product.

References

  1. [1]
    "Indium(III) Chloride". American Elements. Retrieved May 15, 2019.
  2. [2]
    Araki, S.; Hirashita, T. "Indium trichloride" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi:10.1002/047084289X.
  3. [3]
    Indium Trichloride
  4. [4]
    Habeeb, J. J.; Tuck, D. G. "Electrochemical Synthesis of Indium(III) Complexes" Inorganic Syntheses, 1979, volume XIX, ISBN 0-471-04542-X
  5. [5]
    Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0123526515
  6. [6]
    Wells, A.F. Structural Inorganic Chemistry, Oxford: Clarendon Press, 1984. ISBN 0-19-855370-6.
  7. [7]
    Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  8. [8]
    Anthony John Downs (1993). Chemistry of aluminium, gallium, indium, and thallium. Springer. ISBN 0-7514-0103-X.
  9. [9]
    Main Group Metals in Organic Synthesis vol 1, ed. Hisashi Yamamoto, Koichiro Oshima, Wiley VCH, 2004, ISBN 3527305084
  10. [10]
    The Group 13 Metals Aluminium, Gallium, Indium and Thallium: Chemical Patterns and Peculiarities, Simon Aldridge, Anthony J. Downs, Wiley, 2011, ISBN 978-0-470-68191-6
  11. [11]
    Main Group compounds in Inorganic Syntheses, vol 31, By Schultz, Neumayer, Marks; Ed., Alan H. Cowley, John Wiley & Sons, Inc., 1997, ISBN 0471152889
  12. [12]
    An efficient synthesis of novel pyrano[2,3-d]- and furopyrano[2,3-d]pyrimidines via Indium-Catalyzed Multicomponent Domino Reaction Prajapati, D. Mukut Gohain, M. Beilstein Journal of Organic Chemistry 2006, 2:11 doi:10.1186/1860-5397-2-11
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