A number of complexes of iron(II) dichlorides with 2-, 3- and 4-position carbonyl-substituted pyridines, i.e. Fe(RCO-py)2Cl2 (R = CH3, C6H5, H, OH and NH2) have been prepared and characterized by means of Mössbauer, IR spectroscopy and magnetic measurements. These complexes have distorted octahedral structures. The quadrupole splittings (ΔEO) for the 2-position substituted complexes are much larger than those of 3-, or 4-position substituted complexes, since the 2- and 3-, 4-derivatives do not coordinate in the same way. The 2-substituted complexes are bidentate and the 3- and 4-substituted complexes are monodentate. The ground state 3d orbital of the iron in the complexes was identified and the energy separation of the levels estimated. The effect on the isomer shift of substituent group(R) in the 2-position substituted complexes is discussed.
Journal of inorganic and nuclear chemistry 40(2), pp.221-224