STRUCTURE OF TETRAKIS-PIVALOYLTRIFLUOROACETONATES OF HEAVY RARE-EARTHELEMENTS AND SODIUM - CRYSTAL-STRUCTURE OF NAER(C8H10O2F3)(4)

The structure of a compound from an isostructural series of pivaloyltr ifluoroacetonates of heavy rare-earth elements (REE) (Cd-Lu) and sodiu m, NaEr(C8H10O2F3)(4), was studied by X-ray diffractometry (''Syntex P 2(1),'' lambda MoKalpha, 1891 reflections R = 0.0601); a = 13.114(4), c = 21.004(9) Angstrom, V = 3128(2) Angstrom(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 poly hedron of Ln is a tetragonal antiprism, an ssss stereoisomer. Na is su rrounded by 4O + 4F in the form of an octahedron with two centered fac es. Both polyhedra are distorted (average Er-O distances are 2.325 Ang strom Na-O 2.397 Angstrom Na-F 2.682 Angstrom) and linked by common fa ces into polymeric helicoidal ribbons extended along the c axis and ar ranged according to the closest packing law. It is established that th e Na cation affects the stereochemistry of the anion. A relationship b etween the structure of the compound and ifs volatility and crystal mo rphology is discussed.