Cobalt(II), nickel(II) and copper(II) compounds derived from template reactions of enantiomerically pure 2-amino-thiazoles

Herein we report the syntheses and structural analyses of three coordination compounds Co(L)2 (3), Ni(L)2, (4) and Cu(L)2 (5) (L = bis[(4R,5R)-4-methyl-5-phenyl-4,5-dihydro-thiazol-2-yl]-amine) prepared by template reactions from the optically active ligand (4R,5R)-4-methyl-5-phenyl-4,5-dihydro-thiazol-2-yl-amine (1) and CoCl2·6H2O, NiBr2·3H2O or Cu(OAc)2·H2O The template reactions involve the condensation of two molecules of thiazol-2-yl-amine and elimination of one NH3. The resulting bidentate ligand coordinates to the metal ion through the imine nitrogen atoms forming a six-membered ring, presenting an electronic delocalization which averages the four M–N bond lengths. The distorted tetrahedral geometry of the metal atoms gives place to complex electronic spectra for compounds 3–5. A mixed ionic compound (6) formed by three cations (4S,5S)-3,4-dimethyl-5-phenyl-thiazolidin-2-ylidene ammonium, one dianion tris-(thiocyano)bromide cobaltate and one bromide, obtained from reaction of (4S,5S)-3,4-dimethyl-5-phenyl-thiazolidin-2-ylidene ammonium thiocyanate (2) and CoBr2 is also described. Compounds 3–6 were characterized in the solid state by UV–Vis–NIR and IR spectroscopy, mass spectrometry and X-ray diffraction analyses. Metal···H–C, S···H–C interactions were observed in 3–6, whereas in 6, also Br···H–N, Br···H–C and Br···S, S···S short contacts were found.

Graphical abstractThree coordination compounds Co(L)2, Ni(L)2, and Cu(L)2 (L = bis[(4R,5R)-4-methyl-5-phenyl-4,5-dihydro-thiazol-2-yl]-amine) prepared by template reactions from the optically active ligand (4R,5R)-4-methyl-5-phenyl-4,5-dihydro-thiazol-2-yl-amine and the metal salts. The ligand coordinates to the metal ion through the imine forming a six-membered ring. A mixed ionic compound with three cations (4S,5S)-3,4-dimethyl-5-phenyl-thiazolidin-2-ylidene ammonium, one dianion tris-(thiocyano)bromide cobaltate and one bromide, is also described.Figure optionsDownload full-size imageDownload as PowerPoint slide