Synthesis and crystal structure of two synthetic oxofluoride framework compounds – Co2TeO3F2 and Co2SeO3F2

Abstract

Two new isostructural Co(2+) containing tellurium and selenium oxofluoride compounds Co(2)TeO(3)F(2) and Co(2)SeO(3)F(2) are synthesized and their structures determined by single crystal X-ray diffraction. They crystallize in the orthorhombic space group Pnma with the unit cell parameters a = 7.3810(5) Å, b = 10.1936(7) Å, c = 5.3013(3) Å and a = 7.2655(8) Å, b = 10.0013(13) Å, c = 5.3564(6) Å, respectively. The Co(II) ion has octahedral coordination [CoO(3)F(3)] and builds up a 3D framework by corner- and edge sharing. The Se(IV) and the Te(IV) ions have the coordinations [SeO(3)E] and [TeO(3)E] respectively where E is the lone-pair electrons. The Se(IV) and Te(IV) ions are isolated from each other and bond only to the [CoO(3)F(3)] polyhedra. The electronegative element fluorine takes the role of a network builder like oxygen and helps to form the 3D framework structure. This is a difference compared to many oxohalide compounds containing Cl and Br where the halide ions are terminating ions preventing a 3D network from being formed. Long range antiferromagnetic interactions dominate at temperatures < 20 K. The magnetic susceptibility follows the Curie-Weiss law above 25 K with the Curie constant C = 5.62 emu K mol(-1), the Weiss temperature θ = -56 K and the effective magnetic moment μ(eff) = 4.74 μ(B) per cobalt atom.

[NaCl][Cu(HSeO3)2], NaCl-intercalated Cu(HSeO3)2: synthesis, crystal structure and comparison with related compounds

“…Transition metal selenites have been the focus of a number of recent studies due to their interesting physical properties, arising in part due to the interplay between the stereochemical activity of lone pairs of electrons on the Se 4+ cations and electronic properties of transition metal cations [1][2][3][4][5][6][7][8][9]. The interest has also been stimulated by the attempts to understand purely fundamental reasons for structural diversity in selenites and its underlying crystal chemical mechanisms [10][11][12].…”

Lone-pair self-containment in pyritohedron-shaped closed cavities: optimized hydrothermal synthesis, structure, magnetism and lattice thermal conductivity of Co15F2(TeO3)14

“…20 On the other hand, the smaller fluoride anion may act as a bridging species between transition metal cations in phases such as V2Te2O7F2, 21 MTeO3F (M = Fe, Ga), 22 Co2TeO3F2, and Co2SeO3F2. 23 It may also be noted that there exist different bonding preferences between the transition metal cation and lone-pair cation. Transition metal cations prefer to bond with both oxygen and halide anions, while lone-pair cations prefer exclusively to coordinate to oxide anions.…”

Transition Metal Selenite Halides: A Fascinating Family of Magnetic Compounds

“…Fluoride compounds usually show different behavior and tendencies due to the peculiarities of fluorine and fluorides sometimes are closer to pure oxide compounds. Moreover, the literature data about selenite fluorides or oxofluorides of d-metals are rather limited and describe only a small number of compounds [18][19][20][21].…”