[M(18-crown-6)X][N(Tf)2] (M: Zn, Co; X: I, N(Tf)2) with unusual crown-ether coordination

•Ionic liquid based synthesis of [M(18-crown-6)X][N(Tf)2](M: Zn, Co; X: I, N(Tf)2).•[M(18-crown-6)X]+ cation (M: Zn, Co; X: I, N(Tf)2).•Sevenfold coordination of Zn2+/Co2+.•Unusually twisted 18-crown-6 molecule as a ligand.

[M(18-crown-6)X][N(Tf)2] (M: Zn, Co; X: I, N(Tf)2) is obtained by reacting equimolar amounts of MI2 and 18-crown-6 with an excess of I2 in the ionic liquid [NMe(n-Bu)3]2[N(Tf)2] at 100 °C. The cationic complexes [Zn(18-crown-6)I]+ and [Co(18-crown-6)N(Tf)2]+ exhibit an unusual sevenfold coordination of Zn2+/Co2+ and an unusually twisted 18-crown-6 molecule as a ligand. The structural arrangement is ascribed to the small radius of Zn2+/Co2+, the weakly coordinating features of the ionic liquid and the stabilization of the [Zn(18-crown-6)I]+ and [Co(18-crown-6)N(Tf)2]+ cations via hydrogen-bridge bonding.

Graphical abstract[M(18-crown-6)X][N(Tf)2] (M: Zn, Co; X: I, N(Tf)2) show an unusual coordination and twisted conformation of 18-crown-6.Figure optionsDownload full-size imageDownload as PowerPoint slide