SYNTHESIS AND X-RAY-POWDER DIFFRACTION DATA FOR MNBF6 (M=FE, CO) COMPOUNDS

X-ray diffraction experiments performed on the compounds (FeNbF6)-Nb-I I-F-IV and (CoNbF6)-Nb-II-F-IV have shown that they crystallize in the rhombohedral system, space group <R(3)over bar> with a cationic order ing. Unit cell parameters were determined: a = 5.4201(8) Angstrom, c = 14.072(2) Angstrom, V = 357.8(1) Angstrom, Z =3 for FeNbF6, and a = 5 .351(2) Angstrom, c = 13.960(6) Angstrom, V = 346.2(2) Angstrom, Z = 3 for CoNbF6. Synthesis and powder diffraction data are reported. (C) 1 998 International Centre for Diffraction Data. [S0885-7156(97)00501-0]