Synthesis and crystal structure of octa(ε-caprolactam)neodymium(III) hexa(isothiocyanate)chromate(III)

The novel mixed-ligand ionic complex compound [Nd(ε-caprolactam)8][Cr(NCS)6] was prepared by the reaction between NdCl3, ε-caprolactam and K3[Cr(NCS)6] in water solution and structurally characterized. Crystals are triclinic, space group image, a = 14.2438(6) AA, b = 14.5641(6) Å, c = 17.0308(7) Å, α = 92.5180(10)°, β = 91.0130(10)°, γ = 108.6020(10)°, V = 3343.3(2) Å3, Z = 2, T = 90 K, Dx = 1.440 g cm−3, R = 0.0342 for 16,296 (I > 2σI). Caprolactam ligands are completely ordered. The neodymium(III) atom is in distorted square-antiprismatic environment of eight oxygen atoms of L ligands, Nd–O = 2.37–2.54 Å. NH groups of caprolactam ligands are involved in hydrogen bonding forming NH…O intramolecular and NH…S(CN) inter-ionic contacts so that each cation is joined to three anions and vice versa.