Gallium Halides - Trihalides

Trihalides

All four trihalides are known. They all contain gallium in the +3 oxidation state. Their proper names are gallium(III) fluoride, gallium(III) chloride, gallium(III) bromide and gallium(III) iodide.

GaF₃

GaF₃ is a white solid which sublimes before it melts, with an estimated melting point above 1000 °C. It contains 6 co-ordinate gallium atoms with a three-dimensional network of GaF₆ octahedra sharing common corners.

GaCl₃, GaBr₃ and GaI₃

These all have lower melting points than GaF₃, (GaCl₃ mp 78 °C, GaBr₃ mp 122 °C, GaI₃ mp 212 °C) reflecting the fact that their structures all contain dimers with 4 coordinate gallium atoms and 2 bridging halogen atoms. They are all Lewis acids, forming mainly 4 co-ordinate adducts. GaCl₃ is the most commonly used trihalide.