Unlike the structures of the three heavier trihalides, aluminium fluoride (AlF3) features six-coordinate aluminium, which explains its involatility and insolubility as well as high heat of formation. Each aluminium atom is surrounded by six fluorine atoms in a distorted octahedral arrangement, with each fluorine atom being shared between the corners of two octahedra.
Unlike the structures of the heavier trihalides, aluminum fluoride (AlF3) has a unique structure where each aluminum atom is surrounded by six fluorine atoms in a distorted octahedron. This configuration contributes to its insolubility and high heat of formation.