Organogallium chemistry

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Trimethylgallium Trimethylgallium-2D.png
Trimethylgallium

Organogallium chemistry is the chemistry of organometallic compounds containing a carbon to gallium (Ga) chemical bond. Despite their high toxicity [ citation needed ], organogallium compounds have some use in organic synthesis. The compound trimethylgallium is of some relevance to MOCVD as a precursor to gallium arsenide via its reaction with arsine at 700 °C:

Contents

Ga(CH3)3 + AsH3 → GaAs + 3CH4

Gallium trichloride is an important reagent for the introduction of gallium into organic compounds.

The main gallium oxidation state is Ga(III), as in all lower group 13 elements (such as aluminium). [1] [2]

Organogallium(I) chemistry

Organometallic complexes of gallium(I) are significantly rarer than that of gallium(III). Some common species include arene-gallium(I) complexes and sterically hindered aryl gallium(I) complexes. [3] [4]

An example of an aryl organogallium(I) compound, note its reversible dimerization Arylgallium(I).png
An example of an aryl organogallium(I) compound, note its reversible dimerization

Organogallium(III) chemistry

Compounds of the type R3Ga are monomeric. Lewis acidity decreases in the order Al > Ga > In and as a result organogallium compounds do not form bridged dimers as organoaluminum compounds do. Organogallium compounds are also less reactive than organoaluminum compounds. They do form stable peroxides. [5]

Organogallium compounds can be synthesized by transmetallation, for example the reaction of gallium metal with dimethylmercury:

2Ga + 3Me2Hg → 2Me3Ga + 3 Hg

or via organolithium compounds or Grignards:

GaCl3 + 3MeMgBr → Me3Ga + 3MgBrCl

The electron-deficient nature of gallium can be removed by complex formation, for example

Me2GaCl + NH3 → [Me2Ga(NH3)Cl]+Cl

Pi complex formation with alkynes is also known.

Organogallium compounds are reagents or intermediates in several classes of organic reactions:

See also

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Gallium compounds are compounds containing the element gallium. These compounds are found primarily in the +3 oxidation state. The +1 oxidation state is also found in some compounds, although it is less common than it is for gallium's heavier congeners indium and thallium. For example, the very stable GaCl2 contains both gallium(I) and gallium(III) and can be formulated as GaIGaIIICl4; in contrast, the monochloride is unstable above 0 °C, disproportionating into elemental gallium and gallium(III) chloride. Compounds containing Ga–Ga bonds are true gallium(II) compounds, such as GaS (which can be formulated as Ga24+(S2−)2) and the dioxan complex Ga2Cl4(C4H8O2)2. There are also compounds of gallium with negative oxidation states, ranging from -5 to -1, most of these compounds being magnesium gallides (MgxGay).

References

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