Structure of tetrakis-pivaloyltrifluoroacetonates of heavy rare earth elements and sodium. Crystal structure of NaEr(C8H10O2F3)4

The structure of a compound from an isostructural series of pivaloyltrifluoroacetonates of heavy rare- earth elements (REE) (Cd- Lu) and sodium, NaEr(C₈H₁₀O₂F₃)₄, was studied by X- ray diffractometry (“Syntex P2₁,” λMoK_α, 1891 reflections, R =0.0601);a =13.114(4), c =21.004(9) å, V =3128(2) å ³, Z =3,space group P3 ₁. The structures of this series are of ionic type and contain the [Ln(pta) ₄]^? complex anion and the Na⁺ cation. The coordination polyhedron of Ln is a tetragonal antiprism, an ssss stereoisomer. Na is surrounded by 4O +4F in the form of an octahedron with two centered faces. Both polyhedra are distorted (average Er- 0 distances are 2.325 å, Na- O 2.397 å, Na- F 2.682 å) and linked by common faces into polymeric helicoidal ribbons extended along the c axis and arranged according to the closest packing law. It is established that the Na cation affects the stereochemistry of the anion. A relationship between the structure of the compound and its volatility and crystal morphology is discussed.