Karl Mennemann

Structure and properties of the fluorine-rich oxofluoromolybdates Cs3[Mo2O6F3], (NH4)3[Mo2O2F9] and (NH4)2[MoOF5]

Abstract The structures of the dinuclear oxofluoromolybdates Cs3[Mo2O6F3] and (NH4)3[Mo2O2F9] and of (NH4)2[MoOF5] were determined by X-ray crystallography. Cs3[Mo2O6F3] crystallizes in the hexagonal space group P6 3 mmc with a = 6.389(1) A , c = 15.100(2) A and Z = 2 . The structure contains the dinuclear anion [Mo2O6F3]3−. The vibrational spectra show that oxygen and fluorine are disordered statistically over the terminal and bridging ligand positions. The main species is the [O2FMoO2FMoO2F] 3− ion. (NH4)3[Mo2O2F9] crystallizes in the trigonal space group P 3 m1 with a = 20.438(3) A , c = 8.096(1) A and Z = 9 . The dinuclear anions are built up from octahedra sharing a corner. The terminal oxygen atoms are located in trans positions to the bridge bond. Approximately 10% of the molybdenum-(V) atoms are oxidized to molybdenum(VI). The additional positive charge is balanced by replacing a fluoro ligand by an oxo ligand. (NH4)2[MoOF5] crystallizes in the orthorhombic space group Cmc21 with a = 6.047(2) A , b = 14.355(5) A , c = 7.056(5) A and Z = 4 . Here molybdenum(V) is also partly substituted by molybdenum(VI).