The oxalato complexes of titanium(IV)—I

Abstract

Abstract--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(C204)22 units, pH studies of solutions of (NI-L)2TiO(C204)2.H20 in 0.5 M NaCIO4 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/31 = 7.90 +-0.02 and log/32 = 13.24 +-0.07, when using hydrolysis constants given by Nazarenko et al.In an attempt to determine the stability constant/32 spectrophotometrically using an exchange method with pyrocatechol, a mixed ligand complex was found with a Ti:pyrocatechol:oxalate ratio of 1:1:1.

Synthesis and Characterization of TiO2 Nanocrystals Prepared from n-Octadecylamine−Titanyl Oxalate Langmuir−Blodgett Films

“…Similar deposition attempts for the transfer of TiO 2 on the substrates were also carried out at pH = 1 for the subphase, obtained through controlled additions of diluted HCl. But under these circumstances no presence of colloidal TiO 2 onto the substrate has been detected, according to the distribution diagram proposed in ref in the case of (NH 4 ) 2 TiO(C 2 O 4 ) 2 . At this pH value, the Ti(OH) 4 concentration is practically negligible, while [Ti(OH) 2 (C 2 O 4 ) 2 ] 2- and Ti(OH) 2 (H 2 O) 2 (C 2 O 4 ) 2 are the prevalent species.…”

“…The subphase pH has been explained by other researchers through the existence of titanium hydroxo colloids: …”

“…Additionally, what makes the subject even more complex is that titanium aqueous solution chemistry is characterized by the development of several complexes and by sensitivity to processing parameters such as pH, temperature, concentration, and kind of anion. For example, Van De Velde in his studies on oxalate complexes of Ti(IV) in solution asserts that for pH above 3.0 it is possible to have Ti(OH) 4 precipitation . Furthermore, the distribution diagram proposed by Van de Velde in the case of (NH 4 ) 2 TiO(C 2 O 4 ) 2 evidences that at pH = 3.9 the species in solution are [Ti(OH) 2 (C 2 O 4 ) 2 ] 2- (about 80%) and Ti(OH) 4 (for the remaining 20%).…”

“…The investigation aimed at clearing up and proposing a mechanism accounting for the film formation is also supported by other experimental data reported in the literature. Titanyl oxygens exhibit a larger basicity with respect to other metals [for example, V(IV)]; it is also specified that the second protonation of titanyl is easier than the first one, and the rationale is that the stability loss induced by protonation of the yl bond is more influential than the charge effect. It has been already observed that lysine and glutammic acid adsorb on the colloidal TiO 2 surface even with the occurrence of physically powerful electrostatic repulsion. , In this case the formation of hydrogen bonding has been advocated between the protonated amino group of stearylamine and TiO 2 surface hydroxyl groups.…”

Exploring titanium(IV) chemical proximity to iron(III) to elucidate a function for Ti(IV) in the human body

“…3. Citric acid [39–43], lactic acid [44], and oxalic acid [45, 46] are able to coordinate Ti(IV) through carboxylate moieties. Citric acid and lactic acid also bind through hydroxylate groups, a property they share with ascorbic acid [47–49].…”