Solid-state and theoretical structural study on trans-[ReO2(Eten)2]CF3SO3.LiCF3SO3 (Eten = N-ethyl ethylenediamine)

The solid-state structure of trans-[ReO2(Eten)2]CF3SO3.LiCF3SO3 (Eten=N-ethyl ethylenediamine) crystallizing in the triclinic space group, P1-bar, is reported. The title compound crystallizes as two independent trans-[ReO2(Eten)2]+ cations, with each Re atom on an inversion center and a trans orientation with respect to the ethyl functionalized N-donor atom of the Eten ligand. A LiCF3SO3 co-crystallizes with the complexes, wherein the Li+ cation occupies a distorted tetrahedral geometry as defined by four intermolecular oxygen interactions. Two of these are to the oxo ligands of the trans-[ReO2(Eten)2]+ cations, thus forming infinite chains of alternating rhenium complexes and lithium cations. The average Re=O bond length is 1.765(3) Angstroms, with an average bite angle of 79.5(2) degrees, and average Re-N bond distances of 2.191(4) and 2.162(4) Angstroms for the un-functionalized and functionalized N-donor atoms of the Eten ligand, respectively. The two rotamers in the asymmetric unit each have an eclipsed δλ conformation, and DFT optimized structures showed a remarkable agreement with the solid-state data. An energy distribution of eight different conformers were evaluated and correlated with the solid-state structure, spanning a difference of about 13 kJ mol-1, while the rotation barrier of 21.9 kJ mol-1 from eclipsed to staggered conformation was obtained. (authors)