Hydrogen Fluoride Adducts with the Strontium Cation: Sr(HF)3(TaF6)2 and Sr(HF)(BF4)2

Tina Bunič, Melita Tramšek, Evgeny Goreshnik* and Boris Žemva*

Department of Inorganic Chemistry and Technology, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
* Corresponding author: E-mail: evgeny.goreshnik@ijs.siboris.zemva@ijs.si

By slow crystallization from anhydrous HF solution crystals of two new HF adducts with the composition Sr(HF)3(TaF6)2 and Sr(HF)(BF4)2 were obtained and investigated by X-ray single crystal technique and Raman spectroscopy. Sr(HF)3(TaF6)2 (I) crystallizes in a monoclinic P21/c space group, a = 8.663(17) Å, b = 12.714(5) Å, c = 10.759(10) Å, β= 94.24(2)°, V=1181.77(300) Å3, Z = 4. The metal coordination sphere consists of nine fluorine atoms and adopts the shape of tri-capped trigonal prism. Six F atoms belong to six TaF6 anions and 3 fluorine atoms are from three terminal HF molecules. Owing to the bridging function of TaF6 anions infinite double layers lying in bc plane appear. These layers are interconnected into 3-D structure by F–H…F(Ta) hydrogen bonds. Sr(HF)(BF4)2 (II) crystallizes in an orthorhombic Pmn21 space group with a = 5.1566(17) Å, b = 9.637(3) Å, c = 6.900(2) Å, V=342.89(18) Å3, Z = 2. Seven F atoms from BF4 anions and two F atoms from two bridging HF molecules form tri-capped trigonal prismatic surrounding of Sr cation. One of BF4 anions is connected to 4 metal centres, another one to 3 Sr cations and H atom of HF molecule. Owing to bridging function of both HF and BF4 moieties the complex 3-D structure appears.

Keywords: Strontium, weakly bonded anion, HF adduct, TaF6, BF4