Structural and spectroscopic elucidation of imidazolium and pyridinium based hexachloridophosphates and niobates

Abstract

1-Ethyl-3-methylimidazolium hexachloridophosphate, [EMIm][PCl₆] (1), 1-ethyl-3-methylimidazolium hexachloridoniobate, [EMIm][NbCl₆] (2), 1-butyl-4-methylpyridinium hexachloridophosphate, [1,4-BMPy][PCl₆] (3), 1-butyl-4-methylpyridinium hexachloridoniobate, [1,4-BMPy][NbCl₆] (4), and 1-butyl-3-methylpyridinium hexachloridoniobate, [1,3-BMPy] [NbCl₆] (5) have been synthesized and characterized by single-crystal X-ray diffraction and Raman spectroscopy. All the saltlike compounds crystallize in the monoclinic space group: [EMIm][PCl₆] (1): P2₁/c (no. 14), a = 7.698(1), b = 12.266(2), c = 15.019(2) Å, β = 101.45(1)°, V = 1389.9(3) ų and Z = 4; [EMIm][NbCl₆] (2): P2₁/n (no. 14), a = 20.186(1), b = 7.084(1), c = 20.549(1) Å, β = 98.46(1)°, V = 2906.6(4) ų and Z = 8; [1,4-BMPy][PCl₆] (3): P2₁/c (no. 14), a = 14.681(2), b = 7.242(1), c = 16.157(2) Å, β = 101.55(1)°, V = 1683.0(3) ų and Z = 4; [1,4-BMPy][NbCl₆] (4): P2₁/c (no. 14), a = 15.163(2), b = 7.323(1), c = 16.205(2) Å, β = 101.92(1)°, V = 1760.5(4) ų and Z = 4; [1,3-BMPy][NbCl₆] (5): P2₁/c (no. 14), a = 10.396(1), b = 23.050(2), c = 14.974(2) Å, β = 102.28(1)°, V = 3505.9(6) ų and Z = 8. Title compounds are built up by the mentioned bulky organic cations and octahedral [PCl₆]⁻respective [NbCl₆]⁻ anions. No significant hydrogen bonding is observed between the organic cations and respective inorganic anions. FT-Raman spectra of the title compounds have been recorded and interpreted, especially with respect to the inorganic parts [PCl₆]⁻ and [NbCl₆]⁻. NMR spectra and the melting temperatures of 1–5 are given.