Homoleptic Alkaline Earth Metal Bis(trifluoromethanesulfonyl)imide Complex Compounds Obtained from an Ionic Liquid

The first homoleptic alkaline earth bis(trifluoromethanesulfonyl)imide (Tf2N) complexes [mppyr]2[Ca(Tf2N)4], [mppyr]2[Sr(Tf2N)4], and [mppyr][Ba(Tf2N)3] were crystallized from a solution of the respective alkaline earth bis(trifluoromethanesulfonyl)imide and the ionic liquid [mppyr][Tf2N] (mppyr = 1,1-N-methyl-N-propylpyrrolidinium). In
the calcium and strontium compounds, the alkaline earth metal (AE) is coordinated by four bidentately chelating
Tf2N ligands to form isolated (distorted) square antiprismatic [AE(Tf2N)4]2- complexes which are separated by
N-methyl-N-propylpyrrolidinium cations. In contrast, the barium compound, [mppyr][Ba(Tf2N)3], forms an extended
structure. Here the alkaline earth cation is surrounded by six oxygen atoms belonging to three Tf2N- anions which
coordinate in a bidentate chelating fashion. Three further oxygen atoms of the same ligands are linking the Ba2+
cations to infinite

[Ba(Tf2N)3] chains.