Tellurium(II) chloride (tellurium dichloride)

Composition and bonding

In TeCl2 the central tellurium atom is formally divalent and is associated with two chloride ligands. The +2 state of tellurium is less common than the +4 state (as in TeCl4), and compounds in this oxidation level often show tendencies to further react or rearrange. The bonding in low-valent tellurium compounds can include contributions from lone pairs on tellurium, and Te–Cl interactions may be covalent with some ionic character. More detailed discussions of tellurium electronic structure are available at element chemistry resources.

Physical properties and behavior

Tellurium(II) chloride is typically described as a moisture-sensitive solid that hydrolyzes on contact with water, producing hydrochloric acid and oxidized tellurium species. It can disproportionate under certain conditions to give a mixture of elemental tellurium and higher-valent tellurium chlorides. Because of this reactivity, pure well-characterized samples are less commonly encountered than TeCl4 and require careful handling and storage under inert atmosphere.

Preparation and reactivity

Preparations reported in the literature often involve controlled reduction of tellurium(IV) chlorides or the reaction of tellurium metal with a chlorine source under conditions that favor the +2 state. TeCl2 reacts readily with water (hydrolysis) and with donor ligands; coordination by donor solvents or chelating ligands can stabilize Te(II) and give isolable complexes. General synthetic notes and safety information can be found at preparation and reactivity.

Uses, significance and related compounds

The principal applications of TeCl2 are in research: it serves as a reagent or intermediate in the synthesis of organotellurium compounds and in studies of low-valent p-block chemistry. Comparatively, tellurium tetrachloride (TeCl4) is a more common reagent and is often used when a stable Te(IV) source is needed. For comparisons among halides and related tellurium species see related tellurium halides.

Precautions and notable facts

Compounds of tellurium can be toxic and malodorous; tellurium chlorides that hydrolyze release corrosive hydrogen chloride gas and oxidized tellurium residues. Work with TeCl2 should be performed in a fume hood with appropriate protective equipment and under inert conditions when required. Further reading on safety and handling is available at safety guidance.

• Typical behaviors: hydrolysis, disproportionation, ligand stabilization.
• Compared to TeCl4: less stable, more reactive, primarily of research interest.