(S)-Alanine ethyl ester tetra­cyanidoborate, (C5H12NO)[B(CN)4]

The title mol­ecular salt, C5H12NO+·C4BN4− or (C5H12NO)[B(CN)4], was obtained as single crystals by slow evaporation of a solution of the compound in aceto­nitrile over several weeks. The asymmetric unit contains two (S)-alanine ethyl ester cations and two tetra­cyanidoborate anions, which are linked by N—H...N hydrogen bonds. The compound exhibits a relatively low melting point of 110°C and shows a solid–solid phase transition near room temperature (Ts–s = 29°C) on the basis of DSC measurements.