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

Two novel metal chelates with MN₂S₂ coordination: bis[N-(2-pyridyl)thiosalicylidene-kS-amino-kN]nickel(II) 1 and bis{1-isopropyl-3-methyl-4-[N-(2-pyridyl)imino-kN-methyl]pyrazole-5-thiolato-kS}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&z.dotdot;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&z.dotdot;S distance 3.178(4) Å].