The synthesis and characterization of transition-metal coordi-oxygen atoms of the four organic ligands. The non-participation of the pyridine nitrogen atom is unusual. The two water nation compounds containing the ligand diethyl 2-quinolylmethylphosphonate (2-qmpe) is described. Complexes of molecules occupy the fifth and the sixth coordination sites in a trans configuration. The coordinated water molecules are Co II , Mn II , Ni II , Cd II , and Zn II were found to be mutually isomorphous according to their X-ray powder diffraction pat-strongly hydrogen-bonded to the pyridine nitrogen atom of the 2-qmpe, further stabilizing the solid-state structure. The terns and IR spectra. The new coordination compounds were identified and characterized by elemental analysis, magnetic geometry of the metal ion can be described as distorted octahedral. For the Cu II complex, a hydroxo-bridged dinuclear measurements, infrared and ligand-field spectra. The crystal structures of the complexes [M(2-qmpe) 4 (H 2 O) 2 ](ClO 4 ) 2 (M = structure of the type [Cu(2-qmpe) 2 (OH)(H 2 O) 2 ] 2 (ClO 4 ) 2 is proposed, based on its spectroscopic and magnetic proper-Ni, 1; Mn, 2) reveal six-coordinate [M(2-qmpe) 4 (H 2 O) 2 ] cations with the qmpe ligand coordinating via the oxygen rather ties. Ligand-field spectra of the Co and Ni compounds were found to be in agreement with the tetragonally distorted oc-than via the nitrogen atom, as well as lattice perchlorate anions. The metal ion is octahedrally surrounded by the four tahedral geometry.