Cu(VO)(SeO3)(2) (A) and (B) forms: Synthesis and crystal structures of newcopper(II)-vanadyl(IV) diselenites

Two forms of copper(II) vanadyl(IV) diselenite CuVO(SeO3)(2) have been synt hesized by solid state reaction. The form (A) belongs to the monoclinic sys tem space group P2(1)/c with a = 7.983(1) Angstrom, b = 8.877(2) Angstrom, 8.437(2) A, and beta = 100.62(2)degrees, It is a layered structure built up of CuO6 and VO6 octahedra associated, respectively, by pairs via edge shar ing which are making [Cu2O10] and [V2O10] dimers, These dimers are building a layer [CuVO7](n) upon which are fixed the selenium (IV) cations, The lon e pairs of the selenium (IV) are packed in a double layer perpendicular to the [001] direction. Form (B) crystallizes in the orthorhombic system, spac e group Pnma with 7.071(2) A, b = 8.223(2) Angstrom, and c = 9.500(2) Angst rom The structure also exhibits dimers associated via edge and corner shari ng along the [100] and [010] directions, which build up layers parallel to the (001) plane; they are held together by Se-O bonds. The connection via V -O-Cu induces a local order that does not respect the three-dimensional ord er of the network. (C) 1999 Academic Press.