Heheropolyoxo-and Heteropolyoxofluorotungstates A. Review of Syntheses and Procedures

Abstract

This review covers the tabulation of heteropolytungstate anions with the most common structures they adopt, i.e., the Keggin structure and the closely related structures, the Dawson and the Weakley structures. The review also describes the best synthetic procedures to prepare many of these anions. We include in our descriptions the conditions under which each structure will be likely to prevail. At lower pH 4-5, anions having the Dawson structure will be more dominant. In the pH range 6-7, anions having the Keggin or distorted Keggin structure will form. Around pH 8, the Weakley structure will form provided appropriate heteroatoms are present. For the preparation of anions that have the regular 1:12 Keggin structure detailed procedures are included. The review also covers the listing and synthetic procedures for the preparation of fluorinated heteropolytungstate anions in which up to six fluoride ions replace six oxide ions as it happens in large numbers of anions that adopt the Dawson structure. Several fluoride ions replace oxide ions in anions that have the Keggin structure.