New Ionic Liquid Compounds Based on Tantalum Pentachloride TaCl5: Synthesis, Structural, and Spectroscopic Elucidation of the (μ-Oxido)-Chloridotantalates(V) [BMPy][TaCl6], [BMPy]4[(TaCl6)2(Ta2OCl10)], and [EMIm]2[Ta2OCl10]

1-Butyl-4-methylpyridinium hexachloridotantalate(V), [BMPy][TaCl6] (1), tetrakis(1-butyl-4-methylpyridinium) bis(hexachloridotantalate(V) (μ-oxido)-decachloridotantalate(V), [BMPy]4[(TaCl6)2(Ta2OCl10)] (2), and bis(1-ethyl-3-methylimidazolium)-(μ-oxido)-decachloridoditantalate(V), [EMIm]2[Ta2OCl10] (3) were synthesized and characterized by single-crystal X-ray diffraction and vibrational spectroscopy. Compounds 1 and 3 crystallize in the monoclinic space group P21/c (no. 14), whereas compound 2 crystallizes in the triclinic space group P (no. 2). All compounds are built up by the mentioned bulky organic cations and octahedral [TaCl6]– respective linear [Ta2OCl10]2– anions. Coulomb interactions are dominant between the ionic species. FT-IR and FT-Raman spectra were recorded and interpreted, especially with respect to the inorganic species [TaCl6]– (Oh) and [Ta2OCl10]2– (Ci symmetry, approximately D4h). The melting temperatures of compounds 1–3 are given.