Transformation of tri-titanium(IV)-substituted α-keggin polyoxometalate (POM) into tetra-titanium(IV)-substituted POMs: Reaction products of titanium(IV) sulfate with the dimeric keggin POM precursor under acidic conditions

Abstract

Reaction products of titanium(IV) sulfate in HCl-acidic aqueous solution with the dimeric species linked through three intermolecular Ti-O-Ti bonds of the two trititanium(IV)-substituted α-Keggin polyoxometalate (POM) subunits are described. Two novel titanium(IV)-containing α-Keggin POMs were obtained under different conditions. One product was a dimeric species through two intermolecular Ti-O-Ti bonds of the two tetra-titanium(IV)-substituted α-Keggin POM subunits, i.e., [[{Ti(H2O)3}2(μ-O)](α-PW9Ti2O38)]2 6- (1). The other product was a monomeric α-Keggin species containing the tetra-titanium(IV) oxide cluster and two coordinated sulfate ions, i.e., [{Ti4(μ-O)3(SO4)2(H2O)8}(α-PW9O34)]3- (2). Molecular structures of 1 and 2 were also discussed based on host (lacunary site)-guest (titanium atom) chemistry. © 2010 by the authors.