Molecular weight, electrodialysis and anion exchange measurements between pH 1 and 4 showed that the titanyl oxalate anion is present in solution as mononuclear Ti(OH)2(C2O4)22 units. pH studies of solutions of (NH4)2TiO(C2O4)2·H2O in 0.5 M NaClO4 medium and computer evaluation and simulation by LETAGROP and HALTAFALL showed that the behaviour of such solutions can be simulated by applying stability constants of log β1 = 7.90 ± 0.02 and log β2 = 13.24 ± 0.07, when using hydrolysis constants given by Nazarenko et al. In an attempt to determine the stability constant β2 spectrophotometrically using an exchange method with pyrocatechol, a mixed ligand complex was found with a Ti:pyrocatechol:oxalate ratio of 1 : 1 : 1.
van de Velde, G. M. H. (1977). The oxalato complexes of titanium(IV)—I : Mononuclear Ti(OH)2(C2O4)22− in solution. Journal of Inorganic and Nuclear Chemistry, 39(8), 1357-1362. https://doi.org/10.1016/0022-1902(77)80298-4