Syntheses, crystal structures and properties of tetra­kis­(3-methyl­pyridine-κN)bis­(iso­thio­cyanato-κN)manganese(II) and tetra­kis­(3-methyl­pyridine-κN)bis­(iso­thio­cyanato-κN)iron(II)

The reaction of Mn(NCS)$_{2}$ or Fe(NCS)$_{2}$ with 3-methylpyridine (C$_{6}$H$_{7}$N) leads to the formation of two isostructural compounds with compositions [Mn(NCS)$_{2}$(C$_{6}$H$_{7}$N)$_{4}$] ($\textbf{1}$) and [Fe(NCS)$_{2}$(C$_{6}$H$_{7}$N)$_{4}$] ($\textbf{2}$). IR spectroscopic investigations indicate that only terminally coordinated thiocyanate anions are present. This is confirmed by single-crystal structure analysis, which shows that their crystal structures consist of discrete centrosymmetric complexes, in which the metal cations are octahedrally coordinated by two N-bonded thiocyanate anions and four 3-methylpyridine ligands. X-ray powder diffraction (XRPD) proves that pure samples have been obtained. Thermogravimetric measurements show that decomposition starts at about 90$^{\circ}$C and that the two coligands are removed in one step for $\textbf{1}$ whereas for $\textbf{2}$ no clearly resolved steps are visible. XRPD measurements of the residue obtained after the first mass loss of $\textbf{1}$ show that a new and unknown crystalline compound has been formed.