Technetium trichloride is an inorganic compound of

technetium Technetium is a chemical element; it has Symbol (chemistry), symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive. Technetium and promethium are the only radioactive elements whose neighbours in the sense ...

and

chlorine Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...

with the formula TcCl₃.

Preparation and properties

Two polymorphs of technetium trichloride are known. The α-polymorph is prepared as a black solid from ditechnetium(III) tetraacetate dichloride and

hydrogen chloride The Chemical compound, compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hyd ...

at 300 °C. It has a bioctahedral structure, consisting of triangular Tc₃Cl₉ units with ''C''_3v symmetry, with each Tc atom coordinated to two Tc neighbors and five chloride ligands (Tc-Tc

bond length In molecular geometry, bond length or bond distance is defined as the average distance between Atomic nucleus, nuclei of two chemical bond, bonded atoms in a molecule. It is a Transferability (chemistry), transferable property of a bond between at ...

2.44

angstrom The angstrom (; ) is a unit of length equal to m; that is, one ten-billionth of a metre, a hundred-millionth of a centimetre, 0.1 nanometre, or 100 picometres. The unit is named after the Swedish physicist Anders Jonas Ångström (1814–18 ...

). The Tc-Tc distances are indicative of double bonded Tc atoms. Tc₃Cl₉ is isostructural to its rhenium homologue, trirhenium nonachloride. β-TcCl₃ is obtained by the reaction between technetium metal and chlorine gas. Its structure consists of infinite layers of edge-sharing octahedra, similar to MoCl₃ and ReCl₃, with distances that also indicate metal-metal bonding. It is less stable than α-TcCl₃ and slowly transforms into it.

References

{{Chlorides Technetium compounds Metal halides Chlorides