Site-specific vanadates Co4Fe3.33(VO4)(6) and Mn3Fe4(VO4)(6)

Single crystals of Co4Fe3.33(VO4)(6) and Mn3Fe4(VO4)(6) were grown from equ ivalent CoO/Fe2O3/V2O5 and MnO/Fe2O3/V2O5 melts, respectively. The former c rystallizes in the orthorhombic space group Pnma with parameters a = 4.965( 1) Angstrom, b = 10.211(1) Angstrom, c = 17.188(3) Angstrom, and Z = 2 and is a homeotype of such catalysts as Mg-2.5-VMoO8. The lader crystallizes in the triclinic space group P (1) over bar with parameters a = 6.703(2) Angs trom, b = 8.137(1) Angstrom, c = 9.801(2) Angstrom, alpha = 105.56(1)degree s, beta = 105.58(2)degrees, gamma = 102.35(1)degrees, and Z = 1 and is a ho meotype of beta-Cu3Fe4(VO4)(6), the low-pressure form of alpha-Cu3Fe4(VO4)( 6). The cobalt analogue deviates in stoichiometry from the reactant melt to form the more dense alpha-Cu3Fe4(VO4)(6) structure type comprised of parti ally occupied face-sharing octahedral and trigonal prismatic coordination s ites.