Bi 6O 4.5(OH) 3.5] 2(NO 3) 11: a new anhydrous bismuth basic nitrate. Synthesis and structure determination from twinned crystals

Abstract

The bismuth basic nitrate [Bi 6O 4.5(OH) 3.5] 2(NO 3) 11 crystallizes in the monoclinic space group P2 1 with a=15.850(3) A ̊ , b=14.986(3) A ̊ , c=18.230(4) A ̊ , β=107.329(17)° and V=4133.7(14) A ̊ 3 (Z=4) . Its structure has been determined from 120 K , twinned crystal X-ray data (16 781 reflections, 683 parameters, R=0.0703). It is built upon [Bi 6O x (OH) 8− x ] (10− x)+ , x=4 and x=5 hexanuclear complexes and nitrate groups. The polycationic entities are linked to the nitrate anions either by hydrogen bonds or through bismuth–oxygen coordination. Even at 120 K , the [Bi 6O 4(OH) 4] 6+ and [Bi 6O 5(OH) 3] 5+ polycations could not be observed as such, the crystal structure refinement only detecting an average [Bi 6O 4.5(OH) 3.5] 5.5+ polycation. To prove the presence of both hexanuclear complexes in the structure, we report the existence of a correlation between the bismuth-linked oxygen bond-valence parameters and the presence, or not, of hydroxyl groups. Moreover, the Raman spectrum of the new anhydrous bismuth basic nitrate is compared to those of [Bi 6O 5(OH) 3](NO 3) 5·3H 2O, [Bi 6O 4(OH) 4](NO 3) 6·4H 2O, and two yet uncharacterized bismuth nitrates.