Composition of overheated vapors and molecular structure of monomeric tris-hexafluoroacetylacetonates of lanthanum, neodymium and samarium

► Structure and vapor composition of Ln(hfa) 3(Ln=La,Nd,Sm) determined by gas electron diffraction and mass-spectrometry. ► Vapors are highly oligomerized. ► Monomeric molecules have D 3-symmetry. ► Lanthanide contraction in the Ln(hfa)3 series is 0.198(18) Å. Molecular structure of lanthanum, neodymium and samarium tris-hexafluoroacetylacetonates has been studied by means of simultaneous gas electron diffraction and mass-spectrometric experiment and quantum-chemical calculations. The coordination polyhedron LnO 6 was confirmed to be a distorted antiprism of D 3-symmetry, and the experimental lanthanide contraction for hfa-complexes within La–Lu series was found to be 0.198(18) Å. Molecular species of La(hfa) 3, Nd(hfa) 3 and Sm(hfa) 3 present in vapor at various degrees of overheating have been identified.