Dimethyl Phthalate, a Neutral Bidentate Oxygen-Donor Ligand to Divalent Metal Ions

A series of new coordination compounds is reported with dimethyl phthalate (MPH) as the ligand, viz. [M(MPH)3](InCl4)2 with M=Mg(II), Ca(II), Mn(II), Fe(II), Co(II), Ni(II), and Zn(II). Each of the metal ions is bonded to three dimethyl phthalate molecules, the six carbonyl oxygens forming a regular octahedron. The carbonyl stretching vibration shifts to lower frequencies, the carbonyl bending vibration shifts to higher frequencies. The magnitudes of the shifts of these vibrations, the frequencies of the metal-ligand vibrations, and the melting points follow the Irving-Williams sequence.