Synthesis, crystal structure and Hirshfeld surface analysis of sodium bis-(malonato)borate monohydrate

In the title salt, poly[aqua-[μ₄-bis-(malonato)borato]sodium], {[Na(C₆H₄BO₈)]·H₂O}_n or Na⁺·[B(C₃H₂O₄)₂]^-·H₂O, the sodium cation exhibits fivefold coordination by four carbonyl O atoms of the bis-(malonato)borate anions and a water O atom. The tetra-hedral B atom at the centre of the anion leads to the formation of a polymeric three-dimensional framework, which is consolidated by C-H⋯O and O-H⋯O hydrogen bonds. A Hirshfeld surface analysis indicates that the most significant contacts in the crystal packing are H⋯O/O⋯H (49.7%), Na⋯O/O⋯Na (16.1%), O⋯O (12.6%), H⋯H (10.7%) and C⋯O/O⋯C (7.3%).