Examining the Out-of-Center Distortion in the [NbOF₅]^2- Anion

Abstract

Out-of-center "primary" electronic distortions are inherent to the oxide fluoride anions of the early d0 transition metals. In the [NbOF5]2- anion, the Nb5+ moves from the center of the octahedron toward the oxide ligand to form a short Nb=O bond and long trans Nb-F bond. The combined results of single-crystal X-ray diffraction and electronic structure calculations indicate that the primary distortion of the [NbOF5]2- anion is affected by the coordination environment that is created by the three-dimensional extended structure. The formation of bonds between an M(L)4(2+) (M = Cd2+, Cu2+; L = 3-aminopyridine, 4-aminopyridine) cation and the oxide and/or trans-fluoride ligands of the [NbOF5]2- anion weakens the pi component of the Nb=O bond. At the same time, hydrogen bond interactions between the equatorial fluorides and the aminopyridine groups both lengthen the equatorial Nb-F bonds and can further reduce the symmetry of the [NbOF5]2- anion. These combined three-dimensional bond network interactions that serve to lengthen the Nb=O bond and thereby decrease the primary distortion of the [NbOF5]2- anion are illustrated in the structures of three new niobium oxide fluoride phases, [4-apyH]2[Cu(4-apy)4(NbOF5)2] (4-apy = 4-aminopyridine), Cd(3-apy)4NbOF5 (3-apy = 3-aminopyridine), and Cu(3-apy)4NbOF5, that were synthesized and characterized using X-ray diffraction. Crystal data for [4-apyH]2[Cu(4-apy)4(NbOF5)2]: tetragonal, space group /4(1)/ acd (No. 142), with a = 20.8745(8) A, c = 17.2929(9) A, and Z= 8. Cd(3-apy)4NbOF5: tetragonal, space group P4(3) (No. 78), with a = 8.4034(4) A, c = 34.933(3) A, and Z = 4. Cu(3-apy)4NbOF5: monoclinic, space group P2(1)/n (No. 14), with a = 8.822(1) A, b = 16.385(3) A, c = 8.902(1) A, beta = 109.270(3) degrees, and Z = 2.

A Fine-Tuned Fluorinated MOF Addresses the Needs for Trace CO2 Removal and Air Capture Using Physisorption

“…As anticipated, the NbOFFIVE-1-Ni can be regarded as a 3-periodic pcu-MOF based on the 2-periodic square grid, Ni-(pyrazine) 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59oxygen atom and one coordinating fluorine atom to the two apical positions in the pillar has been observed and validated in similar materials with supporting techniques. [35][36][37] As expected, the NbOFFIVE-1-Ni encloses a relatively contracted square-shaped channels with a slightly smaller diameter of 3.210(8) Å (derived from the distance between the pendant fluorine centers, F…F, and by taking account van der Walls radii) then the SIFSIX-3-Ni and SIFSIX-3-Cu adsorbents (3.694(1) Å and 3.483(1) Å respectively). It is to mention that the Ni…Ni distance (7.030(3) Å) in the 2-periodic square grid, Ni-(pyrazine) 2 , is preserved and it is the same in both, the NbOFFIVE-1-Ni and SIFSIX-3-Ni adsorbents.…”

Synthesis, Structure, and Characterization of a Layered Mixed Metal Oxychloride, PbVO3Cl

“…This approach has been described earlier with respect to metal oxy-fluoride octahedra. 35,36 We recently reported the dipole moments for BiCl6 octahedra as well using the similar method. Table 4) depending on the degree of distortions.…”

New Layered Oxide-Fluoride Perovskites: KNaNbOF5 and KNaMO2F4 (M = Mo6+, W6+)

“…One well known example Na 3 MoO 3 F 3 , which crystallizes in the cryolite structure and has ordered oxide and fluoride ligands, displays ferroelectric-ferroelastic properties [3]. In this paper, we report a new class of A-site deficient oxyfluoride perovskites ABMO x F 6-x (where A = K + ; B = Na + ; x = 1, M = Nb 5+ ; x = 2, [19,20]. Mid-IR confirms the presence of the Nb=O bond with a peak at ν s 975 cm -1 [21].…”