Coordination properties of the diethyl 2-pyridylmethylphosphonate ligand (2-pmpe) with chloride transition-metal salts: X-ray crystal structure of Cd4(2-pmpe)4Cl8

A new series of the chloride transition-metal complexes containing the ligand diethyl 2-pyridylmethylphosphonate (2-pmpe) of general formula M(2-pmpe)2Cl2 (M = Ni, Co, Mn) and M(2-pmpe)Cl2 (M = Co, Zn,) were prepared. The complexes were identified and characterized by elemental analysis, spectroscopic and magnetic studies. For Cd4(2-pmpe)4Cl8 X-ray crystal structure was determined. The structure is based on a chloro-bridged tetranuclearcadmium quasi cubane cluster, in which each cadmium atom is chelated by one N,O-chelate 2-pmpe ligand and coordinated with four bridging chloride atoms. The ligand containing two donor atoms, heterocyclic pyridyl nitrogen and phosphoryl oxygen atoms binds in a didentate chelate manner in all complexes. Two compounds were obtained with cobalt chloride salt, exhibiting tetrahedral (1:1) and octahedral (1:2 metal to ligand molar ratio) arrangements of cobalt ions. The octahedral Ni(II), Co(II) and Mn(II) complexes are izostructural. Geometry of Zn(2-pmpe)Cl2 is consistent with a pseudotetrahedral environment of Zn(II) ion. The spectroscopic properties of Zn(II), and magnetic behavior of Ni(II), Co(II) and Mn(II) complexes indicate mononuclear structure of all compounds.