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X‐ray crystal structure and raman spectrum of tribromine(1+) hexafluoroarsenate(V), Br 3 + AsF 6 − , and raman spectrum of pentabromine(1+) hexafluoroarsenate(V), Br 5 + AsF 6 −
Author(s) -
Christe K. O.,
Bau R.,
Zhao D.
Publication year - 1991
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.19915930106
Subject(s) - raman spectroscopy , crystallography , crystal structure , x ray crystallography , crystal (programming language) , chemistry , materials science , physics , diffraction , optics , programming language , computer science
A single crystal of Br 3 + AsF 6 − was isolated from a sample of BrF 2 + AsF 6 − which had been stored for 20 years. It was characterized by x‐ray diffraction and Raman spectroscopy. It is shown that Br 3 + AsF 6 − (triclinic, a = 7.644(7) Å, b = 5.641(6) Å, c = 9.810(9) Å, α = 99.16(8)°, β = 86.61(6)°, γ = 100.11(7)°, space group P 1 R(F) = 0.0608) is isomorphous with I 3 + AsF 6 − . The structure consists of discrete Br 3 + and AsF 6 − ions with some cation‐anion interaction causing distortion of the AsF 6 − octahedron. The Br 3 + cation is symmetric with a bond distance of 2.270(5) Å and a bond angle of 102.5(2)°. The three fundamental vibrations of Br 3 + were observed at 297 (ν 3 ), 293 (ν 1 ), and 124 cm −1 (ν 2 ). The Raman spectra of Cl 3 + AsF 6 − and I 3 + AsF 6 − were reinvestigated and ν 3 (B 1 ) of I 3 + was reassigned. General valence force fields are given for the series Cl 3 + , Br 3 + , and I 3 + . Reactions of excess Br 2 with either BrF 2 + AsF 6 − or O 2 + AsF 6 − produce mixtures of Br 3 + AsF 6 − and Br 5 + AsF 6 − . Based on its Raman spectra, the Br 5 + cation possesses a planar, centrosymmetric structure of C 2h symmetry with three semi‐ionically bound, collinear, central Br atoms and two more covalently, perpendicularly bound, terminal Br atoms.