Coordination of Amines to Palladium(II) Complexes of N^21,N^22-Bridged Porphyrins

Pyridine and ethylenediamine reacted with Pd(II) complexes of N^21,N^22-bridged porphyrins to give mixed-ligand Pd(II) complexes. The UV-vis and 1H NMR spectral features of the porphyrin ligand provide information regarding the nature of the coexisting ligands and Pd(II) coordination geometry in the products. That is, the splitting pattern in the Soret region of the UV-vis spectra was dependent on whether porphyrinatopalladium(II) was coordinated by neutral ligands or anionic ligands. In the 1H NMR spectra of ethylenediamine complexes of porphyrinatopalladium(II), signal broadening of porphyrin (beta)-pyrrole protons and a chemical shift change of ethylenediamine protons were seen in the dichloride in comparison with the bis(perchlorate). These phenomena indicate the equilibrium of the coordination and dissociation of chloride and amine at the apical and basal sites in the square pyramid. The H-D exchange in the ethylenediamine ligand was promoted by the presence of chloride.