Synthesis and crystal structure of NaRbB5O8(OH)·H2O.

A new mixed alkali-metal borate, poly[[sodium rubidium [hydroxido-octa-μ-oxido-penta-borate] monohydrate], NaRbB5O8(OH)·H2O, has been synthesized via a surfactant-thermal method using H3BO3, Rb2CO3, Na2SiO3·9H2O, ethanedi-amine and poly(ethyl-ene glycol)-400 as starting materials. It features a layered boron-oxide framework constructed from penta-borate [B5O10(OH)]6- building units. Adjacent single layers are inter-connected to form double layers through hydrogen-bonding inter-actions. Na+, Rb+ cations and H2O mol-ecules are located in the voids of the framework.