Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 9, pp. 1359−1363.
Pleiades Publishing, Ltd., 2013.
Original Russian Text © M.V. Revin, A.N. Artemov, E.V. Sazonova, 2013, published in Zhurnal Prikladnoi Khimii, 2013, Vol. 86, No. 9, pp. 1389−1393.
AND INDUSTRIAL ORGANIC CHEMISTRY
A New Synthetic Route to Trimethylgallium
M. V. Revin, A. N. Artemov, and E. V. Sazonova
Lobachevsky Nizhni Novgorod State University, Nizhni Novgorod, Russia
Received February 20, 2013
Abstract—A new synthetic route to trimethylgallium was developed. It is based on preparation of gallium methyl
derivatives by the Green reaction, followed by their alkylation with methyl Grignard reagent. The suggested pro-
cedure is well reproducible, with the yield of pure trimethylgallium exceeding 90%.
Successful implementation of a process for prepar-
ing semiconductor epitaxial gallium arsenide structures,
accomplished for the ﬁ rst time by Manasevit, gave an
impetus to wide use of trimethylgallium as one of the
main precursors for the production of A
structures, primarily of GaAs, GaN, and Ga
МОCVD (metalorganic chemical vapor deposition) [1,
2]. Today, the most widely used method for commercial
production of high-purity trimethylgallium is the reaction
of a Ga–Mg mixture or alloy with methyl iodide in ether,
following the overall equation [3–5]
2Ga + 3Mg + 6CH
I → 2Ga(CH
·L + 3MgI
where L = (C
O, or THF.
This method is the simplest in implementation, be-
cause the starting compounds do not exhibit high reactiv-
ity toward the surrounding medium, oxygen, and mois-
ture. However, practical experience revealed a number of
signiﬁ cant drawbacks of this route to trimethylgallium,
the main of which is the gallium aggregation (agglutina-
tion of ﬁ ne metal particles) in the course of the reaction.
This phenomenon was more pronounced at larger scales
of the synthesis . At the same time, the occurrence of
a side reaction, dealkylation of the intermediate Grignard
reagent with methyl iodide (Wurtz reaction), makes it
necessary to take magnesium and methyl iodide in excess
relative to the overall reaction stoichiometry [6, 7].
The goal of this study was elimination of the above
drawbacks of the direct synthetic route to trimethylgal-
lium with the aim to optimize the synthesis process and
reduce the production cost. According to published data,
agglomeration may be caused by rapid destruction of
the oxide ﬁ lm on the gallium surface under the action
of Grignard reagent . To conﬁ rm this conclusion, we
performed a synthesis of trimethylgallium by adding a
mixture of gallium metal and methyl iodide to an ether
solution of methylmagnesium iodide prepared in advance.
In this case, the Ga agglomeration was 65%, and the target
product yield did not exceed 10% .
Therefore, it seemed necessary to improve the direct
method for preparing trimethylgallium by dividing it into
two steps . The ﬁ rst step involved a convenient proce-
dure for preparing gallium methyl derivatives, developed
by Green et al. . This method consisted in ultrasonic
activation of a mixture of gallium metal, iodine, and
methyl iodide in a toluene solution. The mechanism of
this reaction involved intermediate formation of highly
reactive gallium monoiodide “GaI” whose further reac-
tion with methyl iodide resulted in rapid dissolution of
the metal with the formation of methylgallium diiodide
as the only product (as stated by the authors):
Ga + 0.5I
“GaI” + CH
I → CH