Syntheses, crystal structures and Raman spectra of Ba(BF4)(PF6), Ba(BF4)(AsF6) and Ba2(BF4)2(AsF6)(H3F4); the first examples of metal salts containing simultaneously tetrahedral BF4- and octahedral AF6- anions

In the system BaF2/BF3/PF5/anhydrous hydrogen fluoride (aHF) a compound Ba(BF4)(PF6) was isolated and characterized by Raman spectroscopy and X-ray diffraction on the single crystal. Ba(BF4)(PF6) crystallizes in a hexagonal P (6) over bar 2m space group with a = 10.2251(4) angstrom, c = 6.1535(4) angstrom(3), V = 557.17(5) angstrom(3) at 200 K, and Z = 3. Both crystallographically independent Ba atoms possess coordination polyhedra in the shape of tri-capped trigonal prisms, which include F atoms from BF4- and PF6- anions. In the analogous system with AsF5 instead of PF5 the compound Ba(BF4)(AsF6) was isolated and characterized. It crystallizes in an orthorhombic Pnma space group with a = 10.415(2) angstrom, b = 6.325(3) angstrom, c = 11.8297(17) angstrom, V = 779.3(4) angstrom(3) at 200 K, and Z = 4. The coordination around Ba atom is in the shape of slightly distorted tri-capped trigonal prism which includes five F atoms from AsF6- and four F atoms from BF4- anions. When the system BaF2/BF3/AsF5/aHF is made basic with an extra addition of BaF2, the compound Ba-2(BF4)(2)(AsF6)(H3F4) was obtained. It crystallizes in a hexagonal P6(3)/MMC space group with a = 6.8709(9) angstrom, c = 17.327(8) angstrom, V = 708.4(4) angstrom(3) at 200 K, and Z = 2. The barium environment in the shape of tetra-capped distorted trigonal prism involves 10 F atoms from four BF4-, three AsF6- and three H3F4- anions. All F atoms, except the central atom in H3F4 moiety, act as mu(2)-bridges yielding a complex 3-D structural network. (C) 2009 Elsevier Inc. All rights reserved.