Crystal structure, synthesis and thermal properties of bis-(aceto-nitrile-κN)bis-(4-benzoyl-pyridine-κN)bis-(iso-thio-cyanato-κN)nickel(II)

Synthesis, characterization and thermal behaviour of solid phases in the quasi-ternary system Mg(SCN)2-H2O-THF

Mg(SCN)2·4H2O can be converted into previously unknown compounds Mg(SCN)2·(4 - x) H2O·xTHF with x = 0, 2 and 4 by multiple recrystallization in tetrahydrofuran (THF). The phases were characterized by infrared spectroscopy (IR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and their crystal structures were solved from X-ray powder diffraction (XRPD) data. In the crystal structures isolated Mg(NCS)2(H2O)4-x(THF)x units form layered motifs. The thermal behavior of Mg(SCN)2·4H2O and Mg(SCN)2·4THF was investigated by temperature dependent in situ XRPD, where Mg(SCN)2·4THF was found to acquire a room temperature (α-form) and high temperature modification (β-form). The phase transformation is associated with an order-disorder transition of the THF molecules and with a reversion of the stacking order of the layered motifs. Further heating eventually leads to the formation of Mg(SCN)2·2THF. There thiocyanate related sulfur atoms fill the voids in the coordination sphere of magnesium, which leads to the formation of one dimensional electroneutral ∞[Mg(NCS)2/2(SCN)2/2(THF)2] chains. All investigated Mg(SCN)2·(4 - x) H2O·xTHF phases exhibit a remarkable anisotropic thermal expansion, and Mg(SCN)2·4H2O and Mg(SCN)2·2THF were found to show both positive and negative thermal expansion coefficients.

Crystal structure, synthesis and thermal properties of bis-(4-benzoyl-pyridine-κN)bis-(iso-thio-cyanato-κN)bis-(methanol-κN)iron(II)

In the crystal structure of the title compound, [Fe(NCS)2(C12H9NO)2(CH4O)2], the FeII cations are octa-hedrally coordinated by two N atoms of 4-benzoyl-pyridine ligands, two N atoms of two terminal iso-thio-cyanate anions and two methanol mol-ecules into discrete complexes that are located on centres of inversion. These complexes are linked via inter-molecular O-H⋯O hydrogen bonds between the methanol O-H H atoms and the carbonyl O atoms of the 4-benzoyl-pyridine ligands, forming layers parallel to (101). Powder X-ray diffraction proved that a pure sample was obtained but that this compound is unstable and transforms into an unknown crystalline phase within several weeks. However, the solvent mol-ecules can be removed by heating in a thermobalance, which for the aged sample as well as the title compound leads to the formation of a compound with the composition Fe(NCS)2(4-benzoyl-pyridine)2, which exhibits a powder pattern that is similar to that of Mn(NCS)2(4-benzoyl-pyridine)2.