Trimethylgallium

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| Watchedfields = changed

| verifiedrevid = 434968600

| ImageFile = Trimethylgallium-2D.png

| ImageName = Structural formula of trimethylgallium

| ImageFile1 = Trimethylgallium-from-xtal-3D-balls.png

| ImageName1 = Ball-and-stick model of trimethylgallium

| IUPACName = trimethylgallane, trimethanidogallium

| OtherNames =

|Section1={{Chembox Identifiers

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChemSpiderID = 14323

| EC_number = 215-897-6

| InChI = 1/3CH3.Ga/h3*1H3;/rC3H9Ga/c1-4(2)3/h1-3H3

| InChIKey = XCZXGTMEAKBVPV-YHXBHQJBAF

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| StdInChI = 1S/3CH3.Ga/h3*1H3;

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| StdInChIKey = XCZXGTMEAKBVPV-UHFFFAOYSA-N

| CASNo_Ref = {{cascite|correct|CAS}}

| CASNo = 1445-79-0

| PubChem = 15051

| SMILES = [Ga](C)(C)C

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|Section2={{Chembox Properties

| Formula = Ga(CH3)3

| MolarMass = 114.827 g/mol

| Appearance = colourless liquid

| Density =

| MeltingPtC = -15

| BoilingPtC = 55.7

| Solubility = Reacts with water

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|Section7={{Chembox Hazards

| MainHazards = Pyrophoric (can ignite spontaneously in air), reacts with water to release methane

| FlashPt =

| AutoignitionPt =

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| Section9 = {{Chembox Related

| OtherCompounds = {{ubl|Triethylgallium|Trimethylborane|Trimethylaluminium|Trimethylindium}}

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Trimethylgallium, often abbreviated to TMG or TMGa, is the organogallium compound with the formula Ga(CH3)3. It is a colorless, pyrophoric liquid.{{cite book |doi=10.1002/9780470132623.ch8|title=Inorganic Syntheses|year=1997|last1=Bradley|first1=D. C.|last2=Chudzynska|first2=H. C.|last3=Harding|first3=I. S.|chapter=Trimethylindium and Trimethylgallium |pages=67–74|volume=31|isbn=978-0-470-13262-3}} Unlike trimethylaluminium, TMG adopts a monomeric structure.{{Greenwood&Earnshaw2nd}} When examined in detail, the monomeric units are clearly linked by multiple weak Ga---C interactions, reminiscent of the situation for trimethylindium.{{cite journal |doi=10.1002/1521-3773(20020715)41:14<2519::AID-ANIE2519>3.0.CO;2-2|title=Luminescence Phenomena and Solid-State Structures of Trimethyl- and Triethylgallium |year=2002 |last1=Mitzel |first1=Norbert W. |last2=Lustig |first2=Christian |last3=Berger |first3=Raphael J. F. |last4=Runeberg |first4=Nino |journal=Angewandte Chemie International Edition |volume=41 |issue=14 |pages=2519–2522 |pmid=12203520 }}

Preparation

Two forms of TMG are typically investigated: Lewis base adducts or TMG itself. All are prepared by reactions of gallium trichloride with various methylating agents. When the methylation is conducted with methylmagnesium iodide in diethyl ether, the product is the poorly volatile diethyl ether adduct. As noted by TMG discoverers Kraus and Toonder in 1933, the ether ligand is not readily lost, although it may be displaced with liquid ammonia.{{ cite journal |author1=Kraus, C. A. |author2=Toonder, F. E. | title = Trimethyl Gallium, Trimethyl Gallium Etherate and Trimethyl Gallium Ammine | journal = PNAS | year = 1933 | volume = 19 | issue = 3 | pages = 292–8 | doi = 10.1073/pnas.19.3.292 | pmc = 1085965 | pmid = 16577510 | bibcode = 1933PNAS...19..292K |doi-access=free }} When the alkylation is conducted with methyl lithium in the presence of a tertiary phosphine the air-stable phosphine adduct is obtained:

:{{chem2| GaCl3 + 3 MeLi + PR3 -> R3P\sGaMe3 + 3 LiCl}}

Heating the solid phosphine adduct under vacuum liberates the base-free TMG:

:{{chem2| R3P\sGaMe3 -> R3P + GaMe3}}

Other non-volatile bases have been described.{{cite book | last1= Foster | first1=Douglas F. | last2= Cole-Hamilton|first2=David J. | title=Inorganic Syntheses | chapter=Electronic Grade Alkyls of Group 12 and 13 Elements|page =29-66|volume=31|year=1997|doi=10.1002/9780470132623.ch7| isbn=978-0-471-15288-0 }}

Other methylating agents for the synthesis of TMG include dimethylzinc and trimethylaluminium.

Applications

TMG is the preferred metalorganic source of gallium for metalorganic vapour phase epitaxy (MOVPE) of gallium-containing compound semiconductors, such as GaAs, GaN, GaP, GaSb, InGaAs, InGaN, AlGaInP, InGaP, AlInGaNP and Ga2O3.{{cite journal | last1 = Shenai-Khatkhate | first1 = D. V. | last2 = Goyette | first2 = R. J. | last3 = Dicarlo | first3 = R. L. Jr | last4 = Dripps | first4 = G. | title = Environment, health and safety issues for sources used in MOVPE growth of compound semiconductors | journal = Journal of Crystal Growth | year = 2004 | volume = 272 | issue = 1–4 | pages = 816–21 | doi = 10.1016/j.jcrysgro.2004.09.007 | bibcode = 2004JCrGr.272..816S }}

These material are used in the production of LED lighting and semiconductors as a metalorganic chemical vapor deposition precursor.

References