| Identifiers | |
|---|---|
3D model (JSmol) | |
| |
| |
| Properties | |
| B9H22Na2O20 | |
| Molar mass | 485.43 g·mol−1 |
| Related compounds | |
Related compounds | Borax Sodium pentaborate Disodium octaborate Trisodium borate Sodium metaborate |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Disodium enneaborate is the traditional name for asalt ofsodium,boron,oxygen, andhydrogen, withelemental formulaNa2B9H22O20 orNa2B9O9·11H2O. It is the sodium borate with the highest boron/sodium ratio.[1]
The correct formula has since been determined to be(Na+)2[B8O11(OH)4]2−·B(OH)3·2H2O. The anion is a linear polymer with repeating unit[−B8O11(OH)4−]2−. Sodium cations, water molecules, and undissociatedboric acid moleculesB(OH)3 lie between the chains, held by numeroushydrogen bonds.[1]
The compound crystallizes in themonoclinic crystal system with space groupP21/n. The cell parameters area = 1021.3pm,b = 1294.0 pm,c = 1245.7 pm, β = 93.070°,V = 1.6440nm3, andZ = 2. The sodium cations occur in groups of four with interatomic distances of 378.30 pm and 379.32 pm.[1]
Upon heating, disodium enneaborate initially becomes amorphous and then crystallizes as anhydrousdisodium octaborate α-Na2B8O13 along with amorphousB2O3. Notably, the former contains octaborate fundamental building blocks that are topologically equivalent to those in the enneaborate.[1]
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