Synthesis and characterization of chromium-isothiocyanate-4-methylpyridine complexes

The synthesis and single crystal X-ray structure of trans-[HNC6H7][Cr(NCS)4(NC6H7)2] (1) and mer-[Cr(NCS)3(NC6H7)3] (2) are reported. Compound 1 was synthesized by refluxing chromium powder and thiourea in 4-methylpyridine. The isothiocyanate ligand is believed to be generated from the isomerization of thiourea to ammonium thiocyanate during synthesis. Compound 2 was prepared from CrCl3 and KSCN in 4-methylpyridine. The reaction conditions for both compounds yielded a mixture of [Cr(NCS)x(NC6H7)6−x]3−x isomers (x = 0–6), which were analyzed by HPLC. The thermal properties of trans-[HNC6H7][Cr(NCS)4(NC6H7)2] were analyzed by thermogravimetric analysis/differential scanning calorimetry–mass spectroscopy (TGA/DSC–MS), and the compound was found to oxidize to CrO2 in three major weight loss steps when heated to 1000 °C in dry air.