Synthesis and crystal structures of palladium(II) complexes of 1,11-bis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane-5,7-dione

The two palladium(II) complexes, [PdL22222][ClO4]2·H2O 1 and [Pd(H−2L22222)]·H2O 2 with 1,11-bis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane-5,7-dione, L22222, were prepared and characterized by X-ray crystallography and UV-visible spectroscopy. In 1 the palladium centre is co-ordinated by the tertiary amines of the macrocycle and the two pyridylmethyl nitrogens, forming a square-planar geometry in which two amide nitrogen groups remain protonated and do not take part in co-ordination. Moreover, there is a weak interaction between palladium and H(–N(8)) [d(PdII ⋯ H) = 2.90 A]. In contrast, 2 isolated under basic conditions has a square-planar geometry but the palladium ion is co-ordi…