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 D3-symmetry. ► Lanthanide contraction in the Ln(hfa)3 series is 0.198(18) Å.