Indium halides

In all of the trihalides the oxidation state of indium is +3, and their proper names are indium(III) fluoride, indium(III) chloride, indium(III) bromide, and indium(III) iodide. The trihalides are Lewis acidic. Indium trichloride is a starting point in the production of trimethylindium which is used in the semiconductor industry.

InF₃ is a white solid, m.p. 1170 °C. Its structure contains 6 coordinate indium.

InCl₃ is a white solid, m.p. 586 °C. It is obtained by oxidation of indium with chlorine.{{cite book|author=E. Donges|chapter=Indium(III) chloride|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=1|pages=858–859}} It is isostructural with AlCl₃.

InBr₃ is a pale yellow solid, m.p. 435 °C. It is isostructural with AlCl₃. It is prepared by combining the elements.{{cite book|author=E. Donges|chapter=Indium(III) bromide|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=1|pages=859–860}} InBr₃ finds some use in organic synthesis as a water tolerant Lewis acid.{{cite journal | last=Zhang | first=Zhan-Hui | title=Indium Tribromide: A Water-Tolerant Green Lewis Acid | journal=Synlett | publisher=Georg Thieme Verlag KG | issue=4 | year=2005 | issn=0936-5214 | doi=10.1055/s-2005-863726 | pages=711–712| doi-access=free }}

File:Indium(III)-iodide-3D-balls.png

InI₃ is a yellow solid. It is obtained by evaporation of a solution of indium in HI.{{cite book|author=E. Donges|chapter=Indium(III) Iodide|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=1|pages=861–2}} Distinct yellow and a red forms are known. The red form undergoes a transition to the yellow at 57 °C. The structure of the red form has not been determined by X-ray crystallography, however spectroscopic evidence indicates that indium may be six coordinate.{{cite journal | last1=Taylor | first1=Michael J. | last2=Kloo | first2=Lars A. | title=Raman investigations of indium iodide complexes: evidence for the In₂I₇⁻ ion | journal=Journal of Raman Spectroscopy | publisher=Wiley | volume=31 | issue=6 | year=2000 | issn=0377-0486 | doi=10.1002/1097-4555(200006)31:6<465::aid-jrs557>3.0.co;2-7 | pages=465–468}} The yellow form consists of In₂I₆ with 4 coordinate indium centres. It is used as an "iodide getter" in the Cativa process.{{citation needed|date=January 2021}}

A surprising number of intermediate chlorides and bromides are known, but only one iodide, and no difluoride. Rather than the apparent oxidation state of +2, these compounds contain indium in the +1 and +3 oxidation states. Thus the diiodide is described as In^IIn^IIIX₄. It was some time later that the existence of compounds containing the anion {{chem2|In2Br6(2-)}} were confirmed which contains an indium-indium bond. Early work on the chlorides and bromides involved investigations of the binary phase diagrams of the trihalides and the related monohalide. Many of the compounds were initially misidentified as many of them are incongruent and decompose before melting. The majority of the previously reported chlorides and bromides have now either had their existence and structures confirmed by X Ray diffraction studies or have been consigned to history. Perhaps the most unexpected case of mistaken identity was the surprising result that a careful reinvestigation of the InCl/InCl₃ binary phase diagram did not find InCl₂.{{cite journal | last1=Meyer | first1=Gerd | last2=Blachnik | first2=Roger | title=Neue Untersuchungen an gemischtvalenten Indium(I, III)- chloriden: Das Phasendiagramm In/Cl im Bereich 30-50 mol-% In und die Kristallstruktur von In₅Cl₉ | journal=Zeitschrift für anorganische und allgemeine Chemie | publisher=Wiley | volume=503 | issue=8 | year=1983 | issn=0044-2313 | doi=10.1002/zaac.19835030813 | pages=126–132 | language=de}}
The reason for this abundance of compounds is that indium forms 4 and 6 coordinate anions containing indium(III) e.g. {{chem2|InBr4(-)}}, {{chem2|InCl6(3-)}} as well as the anion {{chem2|In2Br6(2-)}} that surprisingly contains an indium-indium bond.

In₇Cl₉ is yellow solid stable up to 250 °C that is formulated In^I₆(In^IIICl₆)Cl₃{{cite journal | last1=Beck | first1=Horst Philipp | last2=Wilhelm | first2=Doris | title=In₇Cl₉—A New "Old" Compound in the System In-Cl | journal=Angewandte Chemie International Edition in English | publisher=Wiley | volume=30 | issue=7 | year=1991 | issn=0570-0833 | doi=10.1002/anie.199108241 | pages=824–825}}

In₇Br₉ has a similar structure to In₇Cl₉ and can be formulated as In^I₆(In^IIIBr₆)Br₃{{cite journal | editor-last=Dronskowski | editor-first=R. | title=The crystal structure of In₇Br₉ | journal=Zeitschrift für Kristallographie - Crystalline Materials | publisher=Walter de Gruyter GmbH | volume=210 | issue=12 | date=1995-12-01 | issn=2194-4946 | doi=10.1524/zkri.1995.210.12.920 | pages=920–923| bibcode=1995ZK....210..920D | last1=Dronskowski | first1=R. }}

In₅Br₇ is a pale yellow solid. It is formulated In^I₃(In^II₂Br₆)Br. The In^II₂Br₆ anion has an eclipsed ethane like structure with a metal-metal bond length of 270 pm.{{cite journal | last1=Ruck | first1=Michael | last2=Bärnighausen | first2=Hartmut | title=Zur Polymorphie von In₅Br₇ | journal=Zeitschrift für anorganische und allgemeine Chemie | publisher=Wiley | volume=625 | issue=4 | year=1999 | issn=0044-2313 | doi=10.1002/(sici)1521-3749(199904)625:4<577::aid-zaac577>3.0.co;2-b | pages=577–585 | language=de}}

In₂Cl₃ is colourless and is formulated In^I₃ In^IIICl₆{{cite journal | last=Meyer | first=Gerd | title=Das Indiumsesquichlorid, In₂Cl₃: ein pseudobinäres, gemischtvalentes Indium(I)-hexachloroindat(III) | journal=Zeitschrift für anorganische und allgemeine Chemie | publisher=Wiley | volume=478 | issue=7 | year=1981 | issn=0044-2313 | doi=10.1002/zaac.19814780705 | pages=39–51 | language=de}} In contrast In₂Br₃ contains the In₂Br₆ anion as present in In₅Br₇, and is formulated In^I₂(In^II₂Br₆) with a structure similar to Ga₂Br₃.{{cite journal | last1=Staffel | first1=Thomas | last2=Meyer | first2=Gerd | title=The mono-, sesqui-, and dibromides of indium: InBr, In₂Br₃, and InBr₂ | journal=Zeitschrift für anorganische und allgemeine Chemie | publisher=Wiley | volume=552 | issue=9 | year=1987 | issn=0044-2313 | doi=10.1002/zaac.19875520913 | pages=113–122 | language=de}}

In₄Br₇ is near colourless with a pale greenish yellow tint. It is light sensitive (like TlCl and TlBr) decaying to InBr₂ and In metal. It is a mixed salt containing the {{chem2|InBr4(-)}} and {{chem2|InBr6(3-)}} anions balanced by In⁺ cations. It is formulated In^I₅(In^IIIBr₄)₂(In^IIIBr₆) The reasons for the distorted lattice have been ascribed to an antibonding combination between doubly filled, non-directional indium 5s orbitals and neighboring bromine 4p hybrid orbitals.{{cite journal | last=Dronskowski | first=Richard | title=Synthesis, Structure, and Decay of In₄Br₇ | journal=Angewandte Chemie International Edition in English | publisher=Wiley | volume=34 | issue=10 | date=1995-06-02 | issn=0570-0833 | doi=10.1002/anie.199511261 | pages=1126–1128}}

In₅Cl₉ is formulated as In^I₃In^III₂Cl₉. The {{chem2|In2Cl9(3-)}} anion has two 6 coordinate indium atoms with 3 bridging chlorine atoms, face sharing bioctahedra, with a similar structure to {{chem2|Cr2Cl9(2-)}} and {{chem2|Tl2Cl9(2-)}}.{{cite journal | last=Meyer | first=Gerd | title=Zur Kenntnis der Chloro- und Bromo-Indate (III). A₃In₂Cl₉ (A = Cs, Rb, In, Tl) und Cs₃In₂Br_9−xCl_x (x = 0, 3, 6, 7, 8) | journal=Zeitschrift für anorganische und allgemeine Chemie | publisher=Wiley | volume=445 | issue=1 | year=1978 | issn=0044-2313 | doi=10.1002/zaac.19784450117 | pages=140–146 | language=de}}

InBr₂ is a greenish white crystalline solid, which is formulated In^IIn^III Br₄. It has the same structure as GaCl₂. InBr₂ is soluble in aromatic solvents and some compounds containing η⁶-arene In(I) complexes have been identified. (See hapticity for an explanation of the bonding in such arene-metal ion complexes). With some ligands InBr₂ forms neutral complexes containing an indium-indium bond.{{cite journal | last1=Sinclair | first1=Ian | last2=Worrall | first2=Ian J. | title=Neutral complexes of the indium dihalides | journal=Canadian Journal of Chemistry | publisher=Canadian Science Publishing | volume=60 | issue=6 | date=1982-03-15 | issn=0008-4042 | doi=10.1139/v82-102 | pages=695–698| doi-access=free }}

InI₂ is a yellow solid that is formulated In^IIn^IIII₄.

The solid monohalides InCl, InBr and InI are all unstable with respect to water, decomposing to the metal and indium(III) species. They fall between gallium(I) compounds, which are more reactive and thallium(I) that are stable with respect to water. InI is the most stable. Up until relatively recently the monohalides have been scientific curiosities, however with the discovery that they can be used to prepare indium cluster and chain compounds they are now attracting much more interest.{{cite journal |doi=10.1021/cr068027+|pmid=17212469|year=2007|last1=Pardoe|first1=J. A.|last2=Downs|first2=A. J.|title=Development of the chemistry of indium in formal oxidation States lower than +3|journal=Chemical Reviews|volume=107|issue=1|pages=2–45}}

InF only known as an unstable gaseous compound.

{{main|Indium monochloride}}

The room temperature form of InCl is yellow, with a cubic distorted NaCl structure. The red high temperature (>390 K) form has the \beta-TlI structure.

InBr is a red crystalline solid, mp 285 °C. It has the same structure as \beta-TlI, with an orthorhombic distorted rock salt structure. It can be prepared from indium metal and InBr₃.

InI is a deep red purple crystalline solid. It has the same structure as \beta-TlI. It can be made by direct combination of its constituent elements at high temperature. Alternatively it can be prepared from InI₃ and indium metal in refluxing xylenes.Organic Syntheses, Coll. Vol. 10, p.170 (2004); Vol. 79, p.59 (2002) It is the most stable of the solid monohalides and is soluble in some organic solvents. Solutions of InI in a pyridine/m-xylene mixture are stable below 243 K.

The trihalides are Lewis Acids and form addition compounds with ligands. For InF₃ there are few examples known however for the other halides addition compounds with tetrahedral, trigonal bipyramidal and octahedral coordination geometries are known.

With halide ions there are examples of all of these geometries along with some anions with octahedrally coordinated indium and with bridging halogen atoms, {{chem2|In2X9(3-)}} with three bridging halogen atoms and {{chem2|In2X7(-)}} with just one.

Additionally there are examples of indium with square planar geometry in the InX₅²⁻ ion. The square planar geometry of {{chem2|InCl5(2-)}} was the first found for a main group element.

Salts of {{chem2|InCl4(-)}}, {{chem2|InBr4(-)}} and {{chem2|InI4(-)}} are known. The salt LiInF₄ has been prepared,{{cite journal |doi=10.1107/S0108270191011915|title=Structure of lithium tetrafluoroindate|year=1992|last1=Gravereau|first1=P.|last2=Chaminade|first2=J. P.|last3=Gaewdang|first3=T.|last4=Grannec|first4=J.|last5=Pouchard|first5=M.|last6=Hagenmuller|first6=P.|journal=Acta Crystallographica Section C Crystal Structure Communications|volume=48|issue=5|pages=769–771|bibcode=1992AcCrC..48..769G }}{{cite journal | last1=Gravereau | first1=P. | last2=Chaminade | first2=J. P. | last3=Gaewdang | first3=T. | last4=Grannec | first4=J. | last5=Pouchard | first5=M. | last6=Hagenmuller | first6=P. | title=Structure of lithium tetrafluoroindate | journal=Acta Crystallographica Section C Crystal Structure Communications | publisher=International Union of Crystallography (IUCr) | volume=48 | issue=5 | date=1992-05-15 | issn=0108-2701 | doi=10.1107/s0108270191011915 | pages=769–771| bibcode=1992AcCrC..48..769G }} however it has an unusual layer structure with octahedrally coordinated indium center. Salts of InF₆³⁻, {{chem2|InCl6(3-)}} and {{chem2|InBr6(3-)}} {{cite journal | last=Spiro | first=Thomas G. | title=Raman Spectra of Crystalline Chlorothallates | journal=Inorganic Chemistry | publisher=American Chemical Society (ACS) | volume=4 | issue=9 | year=1965 | issn=0020-1669 | doi=10.1021/ic50031a013 | pages=1290–1293}} have all been made.

The {{chem2|InCl5(2-)}} ion has been found to be square pyramidal in the salt (NEt4)₂InCl₅, with the same structure as (NEt₄)₂ TlCl₅, but is trigonal bipyramidal in tetraphenylphosphonium pentachloroindate acetonitrile solvate.{{cite journal | last1=Bubenheim | first1=W. | last2=Frenzen | first2=G. | last3=Müller | first3=U. | title=Die Chloroindate [PPh₄]₂[In₂Cl₆] und [PPh₄]₂[InCl₅].CH₃CN | journal=Acta Crystallographica Section C Crystal Structure Communications | publisher=International Union of Crystallography (IUCr) | volume=51 | issue=6 | date=1995-06-15 | issn=0108-2701 | doi=10.1107/s0108270194011789 | pages=1120–1124| bibcode=1995AcCrC..51.1120B }}

The {{chem2|InBr5(2-)}} ion has similarly been found square pyramidal, albeit distorted, in the Bis(4-chloropyridinium) salt {{cite journal | last1=Ishihara | first1=Hideta | last2=Dou | first2=Shi-qi | last3=Gesing | first3=Thorsten M | last4=Paulus | first4=Helmut | last5=Fuess | first5=Hartmut | last6=Weiss | first6=Alarich | title=Crystal structures of [(CH₃)₂NH₂]₃InBr₆ and [4-ClC₅H₄NH]₂InBr₅ | journal=Journal of Molecular Structure | publisher=Elsevier BV | volume=471 | issue=1–3 | year=1998 | issn=0022-2860 | doi=10.1016/s0022-2860(98)00444-x | pages=175–182| bibcode=1998JMoSt.471..175I }} and trigonal bipyramidal {{cite journal | last1=Dubenskyy | first1=Vitaly | last2=Ruck | first2=Michael | title=Bi₃₇InBr₄₈: Eine polares Subhalogenid mit Bi₉⁵⁺-Polykationen, komplexen Bromobismutat(III)-Anionen [Bi₃Br₁₃]^4— und [Bi₇Br₃₀]^9— sowie Pentabromoindat(III)-Anionen [InBr₅]^2— | journal=Zeitschrift für anorganische und allgemeine Chemie | publisher=Wiley | volume=629 | issue=3 | year=2003 | issn=0044-2313 | doi=10.1002/zaac.200390062 | pages=375–380 | language=de}} in Bi₃₇InBr₄₈.

The {{chem2|In2X7(-)}} ions contain a single bridging halogen atom. Whether the bridge is bent or linear cannot be determined from the spectra. The chloride and bromide have been detected using electrospray mass spectrometry. The {{chem2|In2I7(-)}} ion has been prepared in the salt CsIn₂I₇.

The caesium salts of {{chem2|In2Cl9(3-)}} and {{chem2|In2Br9(3-)}} both contain binuclear anions with octahedrally coordinated Indium atoms.

In^IX₂⁻ is produced when the In₂X₆²⁻ ion disproportionates. Salts containing the {{chem2|In^{I}X3(2-)}} ions have been made and their vibrational spectra interpreted as showing that they have C_3v symmetry, trigonal pyramidal geometry, with structures similar to the isoelectronic {{chem2|SnX3(-)|auto=1}} ions.

Salts of the chloride, bromide and iodide ions {{chem2|(Bu4N)2In2X6}} have been prepared. In non-aqueous solvents this ion disproportionates to give {{chem2|In^{I}X2-}} and {{chem2|In^{III}X4-}}.

Following the discovery of the In₂Br₆²⁻ a number of related neutral compounds containing the In^II₂X₄ kernel have been formed from the reaction of indium dihalides with neutral ligands. Some chemists refer to these adducts, when used as the starting point for the synthesis of cluster compounds as ‘In₂X₄’ e.g. the TMEDA adduct.{{cite journal | last1=Li | first1=Xiao-Wang | last2=Robinson | first2=Gregory H. | last3=Pennington | first3=William T. | title=Disproportionation of Low Valent Indium Bromide: Synthesis and Molecular Structure of Bis (2, 6-Dimesityl-Phenyl) Indium Bromide, (2, 6-Mes₂C₆H₃)₂InBr (Mes = 2, 4, 6-Me₃C₆H₂). When does Trigonal Planar Become T-Shaped? | journal=Main Group Chemistry | publisher=IOS Press | volume=1 | issue=3 | year=1996 | issn=1024-1221 | doi=10.1080/13583149612331338587 | pages=301–307}}

• [https://www.webelements.com/indium/compounds.html WebElements Periodic Table » Indium » compounds information]
• {{Greenwood&Earnshaw}}
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Category:Indium compounds

Category:Metal halides

Category:Mixed valence compounds