Thermal Properties and Crystal Structures of Rhenium(I) Carbonyl Complexes with Tridentate Ligands: Preparation of Rhenium-Containing Ionic Liquids

Although the coordination chemistry of rhenium complexes is a rapidly expanding research field, little is known about their thermal properties. In this study, we synthesized several rhenium tricarbonyl complexes with tridentate ligands (<b>L</b>) having S or N as donor atoms, <i>fac</i>-[Re­(CO)₃<b>L</b>]­X (X = Tf₂N [= bis­(trifluoromethanesulfonyl)­amide)], PF₆) and <i>fac</i>-[Re­(CO)₃<b>L</b>Cl], and investigated their thermal properties and crystal structures. The Tf₂N salts were room temperature ionic liquids. The S-coordinated complexes, having longer coordination bonds, were less thermally stable than the N-coordinated complexes. Even though <i>fac</i>-[Re­(CO)₃<b>L</b>Cl] are bidentate coordination complexes, they were thermally more stable than the isomeric tridentate complexes <i>fac</i>-[Re­(CO)₃<b>L</b>]­Cl.