Volatile and Thermally Stable Polymeric Tin Trifluoroacetates.

Area of Science:

• Materials Science
• Inorganic Chemistry
• Solid-State Chemistry

Background:

• Tin trifluoroacetates are established single-source precursors for F-doped SnO2.
• The precise solid and gas phase structures of these compounds have remained largely unknown for decades.

Purpose of the Study:

• To elucidate the complex structures of tin trifluoroacetates in both solid and gas phases.
• To understand their thermal decomposition and polymerization behavior for precursor design.

Main Methods:

• Single-crystal X-ray crystallography for solid-state structure determination.
• Gas phase electron diffraction for gas phase molecular structure analysis.
• Density functional theory (DFT) calculations for theoretical validation.

Main Results:

• Tin(II) bis(trifluoroacetate) (1) undergoes thermal decomposition and polymerization to hexatin(II)-di-μ3-oxyoctakis(μ-trifluoroacetate) (3) upon sublimation and solidification.
• Tin(IV) tetrakis(trifluoroacetate) (5) is polymeric in the solid state but evaporates as a monomer at lower temperatures than (3).
• Polymerization of (5) surprisingly enhances volatility due to entropic effects during sublimation.

Conclusions:

• The structural complexity and thermal dynamics of tin trifluoroacetates are critical for their function as vapor phase precursors.
• Understanding these relationships provides a strategic pathway for designing improved precursors for F-doped SnO2 deposition.
• The counterintuitive volatility enhancement in polymeric tin(IV) tetrakis(trifluoroacetate) presents a novel design principle for precursors.