NEW TUBULAR TRANSITION-METAL OXOANIONIC DERIVATIVES - A SYSTEMATIC-APPROACH TO CONDENSED PHASES OF THE DUMORTIERITE FAMILY

An unified synthetic approach has allowed us to isolate a wide set of highly condensed oxoanionic derivatives of transition metals by using solution chemistry procedures. New phases are described [Ni12+xH6-2x(A sO4)8(OH)6. Ni6(SeO3)4(OH)4], and the preparation of other already kno wn [Ni12+xH6-2x(PO4)8(OH)6, Ni3Te2O6(OH)2] is significantly simplified . The structure of these derivatives, as well as that of other phases such as M11(HPO3)8(OH)6 (M=Zn, Co, Ni), previously characterized by us , can be related to that of the dumortierite mineral. The main feature s of the tubular channels that characterize this structure and the pos sibility to modulate their chemistry are discussed on the basis of the nature of both cationic and anionic components.