Gallium (III) chloride is used as lewis acid or precursor of organogallium reagents. It is used in detection of solar neutrinos. It is used in semiconductor devices for microelectronics and optics.

Microtubule-disrupting effects of gallium(III) chloride

Gallium(III) chloride (GaCl3), an antitumor agent with antagonistic action on iron, magnesium and calcium, was tested for its ability to alter the polymerization of purified tubulin (2.2 mg/ml) in a cell-free system in vitro. GaCl3 (250 microM) does not mimic the effect of 10 microM paclitaxel and, therefore, is not a microtubule (MT)-stabilizing agent that can promote tubulin polymerization in the absence of glycerol and block MT disassembly. In contrast, GaCl3 mimics the effect of 1 microM vincristine (VCR) and inhibits glycerol-induced tubulin polymerization in a concentration-dependent manner (IC50: 125 microM), indicating that Gallium(III) chloride is a MT de-stabilizing agent that prevents MT assembly. However, 150 microM GaCl3 must be used to match or surpass the inhibitions of tubulin polymerization caused by 0.25 microM of known MT de-stabilizing agents, such as colchicine (CLC), nocodazole, podophyllotoxin, tubulozole-C and VCR. The inhibitory effect of 250 microM GaCl3 persists in the presence of up to 9 mM MgCl2, suggesting that the exogenous Mg2+ cations absolutely required for the binding of GTP to tubulin and MT assembly cannot overcome the antitubulin action of Ga3+ ions of a higher valence. The binding of [3H]vinblastine (VBL) to tubulin (0.5 mg/ml) is inhibited by unlabeled VBL but enhanced by concentrations of GaCl3 > 200 microM.[1]

However, increasing concentrations of Gallium(III) chloride mimic the ability of cold CLC to reduce the amount of [3H]CLC bound to tubulin, suggesting that GaCl3 may interact with the CLC binding site to inhibit tubulin polymerization. The binding of [3H]GTP to tubulin is decreased by unlabeled GTP but markedly enhanced by GaCl3, especially when concentrations of this metal salt of 32 microM or higher are added to the reaction mixture before rather than after the radiolabeled nucleotide. These data suggest that changes in protein conformation following Gallium(III) chloride binding might increase the interactions of tubulin with nucleotides and Vinca alkaloids.Since GaCl3 (100-625 microM) increases the percentage of mitotic cells at 2-4 days, it might arrest tumor cell progression in M phase, but its antimitotic activity is much weaker than that of 0.25 microM VCR. Because the concentrations of Gallium(III) chloride that inhibit tubulin polymerization also increase the mitotic index and decrease the viability of L1210 cells in vitro, the antitubulin and antimitotic effects of GaCl3 might contribute, at least in part, to its antitumor activity.

Chlorination of Pu and U Metal Using GaCl3

The oxidative chlorination of the plutonium metal was achieved through a reaction with gallium(III) chloride (GaCl3). In DME (DME = 1,2-dimethoxyethane) as the solvent, substoichiometric (2.8 equiv) amounts of GaCl3 were added, which consumed roughly 60% of the plutonium metal over the course of 10 days. The salt species [PuCl2(dme)3][GaCl4] was isolated as pale-purple crystals, and both solid-state and solution UV–vis–NIR spectroscopies were consistent with the formation of a trivalent plutonium complex. The analogous reaction was performed with uranium metal, generating a dicationic trivalent uranium complex crystallized as the [UCl(dme)3][GaCl4]2 salt. The extraction of [UCl(dme)3][GaCl4]2 in DME at 70 °C followed by crystallization produced [{U(dme)3}2(μ-Cl3)][GaCl4]3, a product arising from the loss of GaCl3. This method of halogenation worked on a small scale for plutonium and uranium, providing a route to cationic Pu3+ and dicationic U3+ complexes using Gallium(III) chloride in DME.

The conjugate reductant of GaCl3, gallium dichloride (Ga2Cl4), is a stable complex, suggesting that GaCl3 has the potential to serve as a mild oxidant and halide source for the formation of UCl3 and PuCl3 from the respective metal via chlorine transfer, generating Ga2Cl4 as a side product. These negative heats of formation bolster the hypothesis that chlorine transfer from Gallium(III) chloride to plutonium or uranium metal will proceed smoothly. This work explores the products arising from halogen transfer to plutonium and uranium metal using GaCl3 as the oxidizing chlorine transfer agent in DME (DME = 1,2-dimethoxyethane). It is well established that Gallium(III) chloride is found as [GaCl2(dme)2][GaCl4] in DME. The reactivity described herein provides an anhydrous synthetic route to a Pu3+ complex under mild reaction conditions, generating a cationic coordination complex. The same reactivity with uranium generated a U3+ dicationic complex.[2]

Separation of GaCl3 from AlCl3

Separation of Gallium(III) chloride from other associating chloride compounds (e.g. AlCl3, SbCl3, and InCl3) is generally achieved by hydrometallurgical processes. In this study, we explore the separation of GaCl3 from these compounds on the basis of the exceptionally high solubility of GaCl3 in hydrocarbon solvents. We found that GaCl3 can be efficiently extracted by anhydrous n-dodecane from a solid mixture of GaCl3 and AlCl3; on the contrary, SbCl3 and InCl3 significantly reduce the extraction of Gallium(III) chloride. On the basis of Lewis acidity theory and study of the Raman spectra, it is shown that formation of the ionic compound [SbCl2][GaCl4] is responsible for the reduced GaCl3 extraction. Formation of [InCl2][GaCl4] is also likely, but further study is needed to support the existence of this compound. Further making use of the strong Lewis acidity of Gallium(III) chloride, GaCl3 can be efficiently stripped from the loaded n-dodecane phase by solid NaCl through formation of NaGaCl4. The extraction of GaCl3 by n-dodecane, in combination with its stripping by NaCl, is a solvometallurgical process that is essentially different from the hydrometallurgical processes for the separation of GaCl3 and AlCl3.[3]

A preliminary solvometallurgical process using only anhydrous n-dodecane and NaCl has been developed for the separation of GaCl3 and AlCl3, based on the exceptionally high solubility of GaCl3 in hydrocarbon solvents and on its Lewis acidity. Gallium(III) chloride can be efficiently extracted by anhydrous n-dodecane from binary solid mixtures of GaCl3/AlCl3 without formation of ionic compounds by chloride transfer thanks to the similarity of the Lewis acidity of these compounds. The loaded Gallium(III) chloride in n-dodecane can be stripped by NaCl by forming NaGaCl4. This solvometallurgical process is essentially different from, and can be supplementary to, the hydrometallurgical processes for GaCl3 and AlCl3 separations.

References

[1]Perchellet, E M et al. “Microtubule-disrupting effects of gallium chloride in vitro.” Anti-cancer drugs vol. 10,5 (1999): 477-88. doi:10.1097/00001813-199906000-00008

[2]Carpenter SH, Klamm BE, Fetrow TV, Scott BL, Gaunt AJ, Anderson NH, Tondreau AM. Chlorination of Pu and U Metal Using GaCl3. Inorg Chem. 2023 Jun 5;62(22):8462-8466. doi: 10.1021/acs.inorgchem.3c00522. Epub 2023 May 23. PMID: 37220066; PMCID: PMC10246562.

[3]Li Z, Bruynseels B, Zhang Z, Binnemans K. Separation of GaCl3 from AlCl3 by Solid-Liquid Extraction and Stripping Using Anhydrous n-Dodecane and NaCl. Ind Eng Chem Res. 2019 Jul 10;58(27):12459-12464. doi: 10.1021/acs.iecr.9b00768. Epub 2019 Jun 21. PMID: 31327891; PMCID: PMC6630954.