Synthesis, Crystal Structure, and Structural Features of Hexa(isothiocyanate)chromates(III) of Lanthanum(III) and Neodymium(III) Complexes with Nicotinic Acid

摘要

[M(C_5H_5NCOO)_3(H_2O)_2][Cr(NCS)_6] - nH_2O complexes, where M = La and n = 2 (1) or M = Nd and n = 1 (2), were synthesized by reacting M(NO_3)_3 (M = La, Nd, K_3[Cr(NCS)_6]) and nicotinic acid (C_5H_5NCOO) in aqueous solution. Their structure was established by IR spectroscopy and X-ray diffraction analysis. The crystals of complexes 1 and 2 are monoclinic, space group P2_1, Z = 2; for complex l,a = 9.66800( 10) A, b = 25.7662(2) A, c = 15.4843(2) A, β = 106.4700( 10)°, V= 3698.99(7) A~3, ρ_(calcd) = 1.761 g/cm~3; for complex 2, a = 9.53120(10) A, b = 25.5166(4) A, c= 15.3843(3) A, β= 104.9450(10)°, V= 3614.96(10) A~3, ρ_(calcd) = 1.779 g/cm~3. Different hydrate compositions of the given compounds may be due to the specific features of intermolecular interactions in their structures.