β-Technetium trichloride: formation, structure, and first-principles calculations.

Area of Science:

• Solid-state chemistry
• Inorganic chemistry
• Materials science

Background:

• Technetium trichloride (TcCl3) exists in multiple forms.
• Understanding the structural and bonding properties of technetium halides is crucial for materials science.

Purpose of the Study:

• To identify and characterize a new polymorph of technetium trichloride.
• To investigate the structural features and stability of the newly identified phase.

Main Methods:

• Synthesis of beta-technetium trichloride (β-TcCl(3)) via reaction of technetium metal with chlorine gas.
• Structural analysis of the resulting compound.

Main Results:

• Identification of a second polymorph of technetium trichloride, β-TcCl(3).
• The structure features infinite layers of edge-sharing octahedra with a Tc-Tc distance of 2.861(3) Å, indicating metal-metal bonding.
• β-TcCl(3) was found to be less stable than the alpha polymorph, slowly transforming into α-TcCl(3) (Tc(3)Cl(9)) at elevated temperatures.

Conclusions:

• The discovery of β-TcCl(3) expands the known structural diversity of technetium halides.
• The observed metal-metal bonding in β-TcCl(3) provides insights into the electronic properties of technetium compounds.
• The lower stability of β-TcCl(3) compared to α-TcCl(3) is consistent with theoretical predictions and highlights the importance of polymorph stability in chemical synthesis.