Synthesis, Properties, and Structures of Salts with the Reineckate Anion, [CrIII(NCS)4(NH3)2]-, and Large Organic Cations

A series of 9 new Reineckate salts, A[Cr-III(NCS)(4)(NH3)(2)] with various large organic cations A = tetraalkylammonium, [R4N](+), R = n-butyl, n-dodecyl; 1-alkyl-3-methylimidazolium, (RMIm)(+): R = methyl, ethyl, iso-propyl, n-butyl, and n-hexyl; A = 1,3-dimethyl-2,4,5-triphenylimidazolium and A = 1,2,3,4,5-pentamethylimidazolium was synthesized. The melting point of each compound was measured to see if any belongs to the group of metal-containing Ionic Liquids with low melting points. Each compound was further characterized by elemental analysis, NMR, IR, and UV/Vis spectroscopy. From NMR investigations information about the magnetic behavior was derived using the Evans method. It has been found that every compound is paramagnetic with effective magnetic moments of spin-only Cr-III. The structures of the Reineckates with A = tetra-n-butyl-ammonium, tetra-n-dodecyl-ammonium, 1-ethyl-3-methylimidazolium, and 1,2,3,4,5-pentamethylimidazolium were determined by single-crystal X-ray diffraction measurements: (nBu(4)N)[Cr(NCS)(4)(NH3)(2)]: monoclinic, C2/c (no. 15), a = 12.0818(8), b = 10.2425(8), c = 24.222(2) angstrom, beta = 98.324(3)degrees, Z = 4, R1(F)/wR2(F-2) = 0.0332/0.0871; {(C12H25)(4)N}[Cr(NCS)(4)(NH3)(2)]center dot 0.85H(2)O: triclinic, P (1) over bar (no. 2), a = 8.4049(1), b = 20.1525(4), c = 20.7908(4) angstrom, alpha = 67.487(1)degrees, beta = 81.328(1)degrees, gamma = 78.040(1)degrees, Z = 2, R1(F)/wR2(F-2) = 0.0533/0.1343; (EMIm)[Cr(NCS)(4)(NH3)(2)]: orthorhombic, Pbcm (no. 57), a = 8.765(2), b = 15.888(3), c = 14.191(3) angstrom, Z = 4, R1(F)/wR2(F-2) = 0.0466/0.1271; (PeMIm)[Cr(NCS)(4)(NH3)(2)] : monoclinic, P2(1)/n (no. 14), a = 6.0817(2), b = 13.9811(5), c = 25.2902(9) angstrom, beta = 90.075(2)degrees, Z = 4, R1(F)/wR2(F-2)= 0.0405/0.1111.