The Mixed Valence Tungsten(IV,V) Compound Na[W2O2Br6]

✍ Scribed by Yue-Qing Zheng; Karl Peters; Hans Georg von Schnering

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: German
• Weight: 101 KB
• Volume: 624
• Category: Article
• ISSN: 0372-7874
• DOI: 10.1002/(sici)1521-3749(199809)624:9<1415::aid-zaac1415>3.0.co;2-5

✦ Synopsis

The reaction of W 6 Br 12 , NaBr, and WO 2 Br 2 in the presence of Br 2 in a sealed silica tube yields Na[W 2 O 2 Br 6 ] together with WOBr 4 and WO 2 Br 2 in the low temperature zone (temperature gradient 1030/870 K). Na[W 2 O 2 Br 6 ] crystallizes orthorhombically in the space group Immm (no.

71. with a = 3.775 A Ê , b = 10.400 A Ê , c = 13.005 A Ê and Z = 2. Pairs of condensed trans-[WO 2 Br 4 ] octahedra with a common Br 2 edge form along [100] double chains 1 ∞ [W 2 O 4/2 Br 6 ] 1± via the oxygen atoms. The mixed valent tungsten atoms are bonded to W 2 pairs with a 2 c±3 e bond (d(W±W) = 2.946 A Ê , d(W± O) = 1.888 A Ê , d(W±Br b ) = 2.537 A Ê , d(W±Br t ) = 2.535 A Ê , |O±W±O = 177.4°, |Br b ±W±Br b (endocyclic) = 109.0°).

The Na + cations connect the anionic double chains to form two-dimensional layers parallel (001), which interact by van der Waals forces. The cations are eightfold coordinated by a cube of the terminal Br t ligands of the polymeric anions (d(Na±Br) = 3.138 A Ê ). Na[W 2 O 2 Br 6 ] may be discussed as an intercalation compound of the oxide bromide WOBr 3 .