Acta Crystallographica Section B

Structural Science

Volume 63, Part 2 (April 2007)

research papers

Acta Cryst. (2007). B63, 205-215 [ doi:10.1107/S0108768106054942 ]

Octahedral As in M⁺ arsenates - architecture and seven new members

K. Schwendtner and U. Kolitsch

Abstract: Arsenates with arsenic in octahedral coordination are very rare. The present paper provides an overview of all known M⁺ arsenates(V) containing octahedrally coordinated arsenic (M⁺ = Li, Na, K, Rb, Cs, Ag) and the crystal structures (determined from single-crystal X-ray diffraction data) of the following seven new hydrothermally synthesized members belonging to six different structure types, four of which are novel: LiH₂As₃O₉, LiH₃As₂O₇, NaHAs₂O₆-type KHAs₂O₆, KH₃As₄O₁₂ and isotypic RbH₃As₄O₁₂, CsAs₃O₈ and NaH₂As₃O₉-type AgH₂As₃O₉. The main building unit of these compounds is usually an As₄O₁₄ cluster of two edge-sharing AsO₆ octahedra sharing two apical corners each with two AsO₄ tetrahedra. The different connectivity between these clusters defines the different structure types. The novel CsAs₃O₈ structure, based on a derivative of the As₄O₁₄ cluster, is the most condensed of all these M⁺ arsenates, with an O/As ratio of only 2.67 compared with values of 2.75-3.5 for the remaining members. This is achieved through polymerization of the cluster derivatives to infinite chains of edge-sharing AsO₆ octahedra. The ^[4]As/^[6]As ratio drops to only 0.5. All but two of the protonated title compounds show protonated AsO₆ octahedra. Hydrogen bonds range from very strong to weak. An analysis of bond-length distribution and average bond lengths in AsO₆ octahedra in inorganic compounds leads to an overall mean As-O distance for all known AsO₆ octahedra (with R factors < 0.072) of 1.830 (2) Å.

Keywords: alkali arsenates; protonated arsenate octahedra; As-O bond length; connectivity.


	Portable Document Format (PDF) file (114.5 kbytes) [ doi:10.1107/S0108768106054942/sn5044sup9.pdf ] Bond lengths and angles, and bond-valence sums

Notes:

To open or display or play some files, you may need to set your browser up to use the appropriate software. See the full list of file types for an explanation of the different file types and their related mime types and, where available links to sites from where the appropriate software may be obtained.

The download button will force most browsers to prompt for a file name to store the data on your hard disk.

Where possible, images are represented by thumbnails.

Search: From to Advanced search