Mononuclear and homobinuclear o -cresolphthalein complexone complexes with VO 2 , Cr 3 , MoO , and UO 2 2 have been prepared and their structures investigated. The empirical formulas, the mode of bonding, and the geometry of the complexes were obtained from elemental and thermal analyses, IR, electronic and ESR spectra, magnetic moment determinations, DC and CV polarographic studies.