Synthesis and crystal structure of NaCsB5O8(OH)·H2O

Abstract

The solvothermal reaction of H₃BO₃, Cs₂CO₃, NaBO₂·4H₂O, formic acid and ethanol led to a new mixed alkali metal borate, NaCsB₅O₈(OH)·H₂O, sodium caesium penta­borate hydroxide monohydrate. Its crystal structure contains penta­borate [B₅O₁₀(OH)]^6– building units, and displays a layered structure containing nine-membered rings. The layers extend parallel to the ab plane and are stacked along the c axis. Na⁺ and Cs⁺ cations are situated between the layers and bond to oxygen atoms with coordination numbers of 7 and 10, respectively. The water mol­ecule likewise occupies the inter­layer space and is hydrogen-bonded to the layers, both as a donor and an acceptor.