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HP‐CsB 5 O 8 : Synthesis and Characterization of an Outstanding Borate Exhibiting the Simultaneous Linkage of All Structural Units of Borates
Author(s) -
Sohr Gerhard,
Többens Daniel M.,
Schmedt auf der Günne Jörn,
Huppertz Hubert
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201404018
Subject(s) - boron , crystallography , orthorhombic crystal system , chemistry , raman spectroscopy , monoclinic crystal system , crystal structure , physics , organic chemistry , optics
The new cesium pentaborate HP‐CsB 5 O 8 is synthesized under high‐pressure/high‐temperature conditions of 6 GPa and 900 °C in a Walker‐type multianvil apparatus. The compound crystallizes in the orthorhombic space group Pnma ( Z =4) with the parameters a =789.7(1), b =961.2(1), c =836.3(1) pm, V =0.6348(1) nm 3 , R 1 =0.0359 and wR 2 =0.0440 (all data). The new structure type of HP‐CsB 5 O 8 exhibits the simultaneous linkage of trigonal BO 3 groups, corner‐sharing BO 4 tetrahedra, and edge‐sharing BO 4 tetrahedra including the presence of threefold‐coordinated oxygen atoms. With respect to the rich structural chemistry of borates, HP‐CsB 5 O 8 is the second structure type possessing this outstanding combination of the main structural units of borates in one compound. The structure consists of corrugated chains of corner‐ and edge‐sharing BO 4 tetrahedra interconnected through BO 3 groups forming octagonal channels. Inside these channels, cesium is 13+3‐fold coordinated by oxygen atoms. 11 B MQMAS NMR spectra are analyzed to estimate the isotropic chemical shift values and quadrupolar parameters. IR and Raman spectra are obtained and compared to the calculated vibrational frequencies at the Γ‐point. The high‐temperature behavior is examined by means of temperature‐programmed powder diffraction.