Tantalum(V) Chloride: Properties Applications in Organic Chemistry and Healthy Hazards

General Description

Tantalum(V) chloride exhibits a unique dimeric structure and versatile reactivity. It forms complexes with various ligands and plays a significant role in organic synthesis, facilitating the formation of complex molecules through distinct chemical pathways. However, it poses several health hazards, including skin burns upon contact, toxic effects upon ingestion, and inflammation of the lungs upon inhalation. Therefore, careful handling and adherence to safety measures are essential. Regulatory bodies monitor its use to mitigate potential risks. Overall, Tantalum(V) chloride's structure, solubility, and chemical behavior make it intriguing for potential applications in catalysis and coordination chemistry, but its health hazards require cautious management.

Figure 1. Tantalum(V) chloride

Properties

Tantalum(V) chloride, also known as TaCl5, exhibits unique characteristics in both its structure and properties. In terms of structure, Tantalum(V) chloride crystallizes in the monoclinic space group C2/m and forms a dimeric structure with the unit cell containing six molecules of the dimer Ta2Cl10. The tantalum atoms within this dimer occupy the centers of octahedra and are joined by two chlorine-bridge bonds. It's worth noting that while the dimeric structure is retained in non-complexing solvents and molten states, in the vapor state Tantalum(V) chloride exists as a monomeric form with a trigonal bipyramidal structure. In terms of physical properties, the solubility of Tantalum(V) chloride varies across different solvents, with aromatic hydrocarbons such as benzene, toluene, m-xylene, and mesitylene showing increased solubility compared to cyclohexane and carbon tetrachloride. This solubility trend is reflected in the color of the solutions, which deepens from pale yellow to orange. Additionally, solutions of TaCl5 are known to be poor conductors of electricity, indicating little ionization. From a chemical perspective, Tantalum(V) chloride is strongly electrophilic and behaves as a Friedel-Crafts type catalyst similar to AlCl3. It forms adducts with various ligands, showcasing its versatile reactivity. Overall, Tantalum(V) chloride's structure, solubility, and chemical behavior make it an intriguing compound with potential applications in catalysis and coordination chemistry. ¹

Applications in Organic Chemistry

Tantalum(V) chloride plays a significant role in organic synthesis due to its versatile reactivity. One common application of Tantalum(V) chloride in organic synthesis is the formation of stable complexes with ethers. When reacting with ethers such as dimethyl ether or diethyl ether, Tantalum(V) chloride forms adducts like TaCl5(OR2), where R represents methyl or ethyl groups. Furthermore, Tantalum(V) chloride can react with compounds like phosphorus pentachloride and phosphorus oxychloride to form various complexes. For instance, the reaction with phosphorus pentachloride produces [PCl4+][TaCl6], while with phosphorus oxychloride it forms [TaCl5(OPCl3)].  Moreover, Tantalum pentachloride can react with tertiary amines to yield crystalline adducts such as [TaCl5(NMe3)]. Additionally, Tantalum(V) chloride can undergo chloride displacement reactions with triphenyl phosphine oxide to generate oxychlorides like [TaOCl3(OP(C6H5)3)]. In the presence of ammonia or lithium methoxide, Tantalum(V) chloride can undergo ammonolysis and amide-forming reactions, leading to the displacement of chloride ligands and the formation of related derivatives like Ta(OEt)5 or Ta(OMe)4Cl. Overall, the diverse reactivity of Tantalum(V) chloride makes it a valuable reagent in various organic synthesis processes, facilitating the formation of complex molecules through distinct chemical pathways. ²

Healthy Hazards

Tantalum(V) chloride poses several health hazards that individuals should be aware of. When exposed to moist air and water, it decomposes and reacts to produce hydrochloric acid, which can cause burns on the skin. Ingestion of this compound is harmful and can lead to adverse effects. Additionally, Tantalum(V) chloride can act as a dermatotoxin, causing skin burns upon contact. Moreover, inhalation of tantalum fumes or toxic gases and vapors can result in toxic pneumonitis, an inflammation of the lungs. It is crucial to handle this compound with care and ensure proper safety measures are in place to prevent exposure to these health hazards. Regulatory bodies such as REACH and the New Zealand EPA Inventory of Chemical Status monitor the use of Tantalum(V) chloride to mitigate potential risks associated with its toxicity. ¹

Reference

1. Tantalum pentachloride. National Center for Biotechnology Information. 2024; PubChem Compound Summary for CID 24394.

2. Encyclopedia: Tantalum(V) chloride. Chemeurope.

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