The lanthanum tetracyanoborate coordination polymers [EMIM] 1∞[LaNO3{B(CN)4}3(H2O)3] (EMIM = 1-ethyl-3-methylimidazolium) and 1∞[La(NO3)2[B(CN)4](H2O)4] mark first examples of Ln-tetracyanoborates that have been obtained in ionothermal syntheses without further solvents to influence e.g. viscosity. Thereby, the ionic liquid [EMIM][B(CN)4] is fully incorporated into product formation.
![Graphical abstract: Transformation of the ionic liquid [EMIM][B(CN)4] into anionic and neutral lanthanum tetracyanoborate coordination polymers by ionothermal reactions](http://hg.y866.cn/compound/lib/scimg/usr/1/C7CC01378G.jpg)
