Five halogen-free orthoborate salts comprised of three different cations (cholinium, pyrrolidinium and imidazolium) and two orthoborate anions, bis(mandelato)borate and bis(salicylato)borate, were synthesised and characterised by DSC, X-ray diffraction and NMR. DSC measurements revealed that glass transition points of these orthoborate salts are in the temperature range from −18 to −2 °C. In addition, it was found that [EMPy][BScB] and [EMIm][BScB] salts have solid–solid phase transitions below their melting points, i.e. they exhibit typical features of plastic crystals. Salts of the bis(salicylato)borate anion [BScB]⁻ have higher melting points compared with corresponding salts of the bis(mandelato)borate anion [BMB]⁻. Single crystal X-ray diffraction crystallography (for [Chol][BScB] crystals) and solid-state multinuclear (¹³C, ¹¹B and ¹⁵N) NMR spectroscopy were employed for the structural characterisation of [Chol][BScB], [EMPy][BScB] and [EMIm][BScB], which are solids at room temperature: a strong interaction between [BScB]⁻ anions and [Chol]⁺ cations was identified as (i) hydrogen bonding between OH of [Chol]⁺ and carbonyl groups of [BScB]⁻ and (ii) as the inductive C–H⋯π interaction. In the other salt, [EMIm][BScB], anions exhibit π⋯π stacking in combination with C–H⋯π interactions with [EMIm]⁺ cations. These interactions were not identified in [EMPy][BScB] probably because of the lack of aromaticity in cations of the latter system. Our data on the formation of a lanthanum complex with bis(salicylato)borate in the liquid mixture of La³⁺(aq) with [Chol][BScB] suggest that this class of novel ILs can be potentially used in the extraction processes of metal ions of rare earth elements.