Crystal-Chemical Study of two Fluorinated Scandium(III) Complexes

An XRD study is conducted at 150(2) K for two complexes: tris-(1,1-difluoroacetylacetonato)scandium(III) ([Sc(dfac)₃]) and tris-(5,5,6,6,6-pentafluorohexane-2,4-dionato)scandium(III) ([Sc(5Fac)₃]). Crystal data for C₁₅H₁₅F₆O₆Sc: Pbca space group, a = 15.5725(3), b = 13.8414(3), c = 17.2587(3) Å, V = 3720.03(13) Å³, Z = 8; for C₁₈H₁₂F₁₅O₆Sc: \(P\bar{1}\) space group, a = 12.2258(5), b = 13.0513(5), c = 15.6120(6) Å, α = 86.740(1), β = 88.605(1), γ = 81.479(1)°, V = 2459.29(17) Å³, Z = 4. Both structures are composed of neutral molecules, the metal atom coordinates six oxygen atoms of three β-diketone ligands. The Sc–O distances vary from 2.074(3) Å to 2.093(3) Å in [Sc(dfac)₃] and from 2.069(3) Å to 2.118(3) Å in [Sc(5Fac)₃]. The molecules in the crystals of both compounds are connected only Van der Waals interactions and form a pseudo-layered structure with a hexagonal molecular arrangement inside the layer. The shortest Sc⋯Sc distances are 7.673(1) Å in [Sc(dfac)₃] and 7.4359(9) Å and 7.4007(9) Å in [Sc(5Fac)₃]. The analysis of Hirshfeld surfaces shows that H⋯H, F⋯H, and F⋯F are the main intermolecular contacts in the packing of these complexes. A comparison with known tris-β-diketonate scandium complexes is performed, and the influence of the structure and the nature and number of intermolecular interactions in the crystals of the studied compounds on their thermal properties is analyzed.