Dinuclear oxofluorometallates as a new structural type of d ⁰ transition metal oxofluoride compound

Abstract

Five isomorphous d(0) transition metal oxofluoride compounds A(3)[M(2)O(x)F(11-x)]·(AF)(0.333) (A = K, Rb, NH(4); M = Nb, Mo, W; x = 2, 4) have been synthesized from acid fluoride solutions, and their crystal structures have been determined by single-crystal X-ray diffraction. The basic structural building units are dinuclear M(2)X(11) (dimers) formed from NbOF(5) or Mo(W)O(2)F(4) octahedra connected by the fluorine bridging atom. In the Nb(2)O(2)F(9) dimer, the O atoms occupy apical corners. In the M(2)O(4)F(7) (M = Mo, W) dimers two O atoms are also apically placed, whereas the other two O atoms are statistically disordered in equatorial planes. The arrangement of dimers is so that the hexagonal tunnels containing `free' fluoride ions are formed. During the irradiation process the orthorhombic structure of K(3)Nb(2)O(2)F(9)·(KF)(0.333) transforms into a pseudo-trigonal one with a = 23.15 Å, which is the [101] diagonal of the orthorhombic unit cell. The other four trigonal crystals are merohedral twins.

Bonding and Structure of Oxofluoroniobate-Based Glasses

“…Thus, a peak at 30 ppm belongs, probably, to bridging F atoms. The 19 F MAS NMR spectrum of K 3 Nb 2 O 2 F 9 ·(KF) 0.333 (Figure f) consisting of Nb 2 O 2 F 9 3– dimers with the bridging F atom corroborates our assignment. The peak at 32 ppm indicates that the bridging F atom joins two niobium octahedra, so the line at 30 ppm must be assigned to the bridging −Nb–F–Nb– fragment in glass chains.…”

Self‐Assembly through Noncovalent Preorganization of Reactants: Explaining the Formation of a Polyfluoroxometalate

“…An approximation of the most stable structure may be obtained by observing the solid‐state ordering of these molecules. Most interestingly, anions similar to our {W 2 } species, such as [W 2 O 4 F 7 ] 3− , crystallize in a hexagonal arrangement of six anions with 1.61 nm diameter and 0.76 nm height . The average cross‐sectional diameter of this hexamer is 1.37 nm, similar to the diameter of the supramolecular structure of [NaW 2 O 5 F 6 ] 3− in solution, as found by diffusion NMR spectroscopy.…”

Luminescence and Scintillation of [Nb2O2F9]3–-Dimer-Containing Oxide–Fluorides: Cs10(Nb2O2F9)3F, Cs9.4K0.6(Nb2O2F9)3F, and Cs10(Nb2O2F9)3Cl

“…These compounds are new members of the A 10 (Nb 2 O 2 F 9 ) 3 X (A = K, Rb, Cs, NH 4 ; X = F, Cl) family. 36 The three reported compounds all crystallize in the same structure type as the previously reported Rb and NH 4 compounds, whereas the previously reported K compound forms in an orthorhombic distortion of the same structure type. Although the three reported compounds possess three different compositions, they are structurally quite similar and exhibit only minor differences in the site occupants of a single column within a channel by unique halide ions.…”