Direct Evidence for Bidentate Character of Potentially Tridentate N,S-Ligands. Molecular Structures of Bis[N-(2-pyridyl)thiosalicylidene-κS-amino-κN]nickel(II) and Bis{1-isopropyl-3-methyl-4-[N-(2-pyridyl)imino-κN-methyl]pyrazole-5-thiolato-κS}copper(II)

Two novel metal chelates with MN₂S₂ coordination: bis[N-(2-pyridyl)thiosalicylidene-_κS-amino-_κN]nickel(II) 1 and bis{1-isopropyl-3-methyl-4-[N-(2-pyridyl)imino-_κN-methyl]pyrazole-5-thiolato-_κS}copper(II) 2 have been investigated; both contain an additional potentially active nitrogen centre in the α-pyridyl substituents on the imino groups, but X-ray structural investigation shows that in neither case is the pyridyl nitrogen atom coordinated to the metal; complex 1 has a slightly distorted cis-planar configuration with a dihedral angle between the NNiS and N’NiS’planes of 13.5° and a shortened S S distance, 2.864(5) Å, while the Cu atom in 2 has a cis-distorted tetrahedral coordination [dihedral angle between NCuS and N’CuS’ planes 57.6°, S S distance 3.178(4) Å].