Synthesis and characterization of anionic transition metal isothiocyanate complexes prepared from metal powders and thiourea

Three new isothiocyanate-4-methylpyridine anionic compounds were prepared by refluxing metal powders (Mn, Fe, and Cu) with thiourea in 4-methylpyridine (γ-picoline). The isothiocyanate ligand is believed to be generated in situ by the isomerization of thiourea to NH4 +SCN− at reflux temperatures. The complexes (Hpic)2[Mn(NCS)4(pic)2]·2pic (1), (Hpic)2[Fe(NCS)4(pic)2]·2pic (2), and (Hpic)[Cu(NCS)3(pic)2]·pic (3) (where pic=γ-picoline) were characterized by single crystal X-ray crystallography. Compounds 1 and 2 are isostructural with four equatorially bound isothiocyanate ligands and two axially bound γ-picoline molecules. Compound 3 is a five-coordinate Cu(II) molecule with a distorted square pyramidal geometry. Coordinated picoline and two isothiocyanates form the basal plane and the remaining isothiocyanate is bound at the apex. The structural data for compounds 1, 2, and 3 are presented.