Reaction of 2-pyridylmethylthiourea derivatives with [(en) ₂Co(OSO₂CF₃)₂]⁺ induces hypodentate coordination of an ethylenediamine ligand

Pyridylmethylthiourea derivatives coordinate with [(en)2Co(OSO ₂CF₃)₂]+ in a tridentate manner resulting in the formation of a hypodentate ethylenediamine ligand. Four ligands were studied: N-(R)phenyl-N′-2-pyridylmethylthiourea (R≤H (1a), CH ₃ (1b), OCH₃ (1c)) and N-benzyl-N′-2- pyridylmethylthiourea (2). These bind through the sulfur, a deprotonated exo nitrogen, and the pyridyl nitrogen atoms forming four and five-membered rings, respectively. The ligand also coordinates in a bidentate manner through the sulfur and deprotonated endo or exo nitrogen atoms, forming two additional coordination isomers. The solid state structure (X-ray) of one of the bidentate isomers of Co-1b2+ (endo isomer) shows that the coordinated thiourea sulfur induces a structural trans effect of 0.035Å on the trans Co-N bond while that of the tridentate isomer of Co-1a3+ confirms the coordination mode of the ligand and the presence of a protonated hypodentate ethylenediamine ligand as suggested by 1H and 13C NMR spectroscopy.