First Stabilization of 14-Electron Rhodium(I) Complexes by Hemichelation

Hemichelation is emerging as a new mode of coordination where non-covalent interactions crucially contribute to the cohesion of electron-unsaturated organometallic complexes. This study discloses an unprecedented demonstration of this concept to a Group9 metal, that is, Rh-I. The syntheses of new 14-electron Rh-I complexes were achieved by choosing the anti-[((6):(6)-fluorenyl){Cr(CO)(3)}(2)] anion as the ambiphilic hemichelating ligand, which was treated with [{Rh(nbd)Cl}(2)] (nbd=norbornadiene) and [{Rh(CO)(2)Cl}(2)]. The new T-shaped Rh-I hemichelates were characterized by analytical and structural methods. Investigations using the methods of the DFT and electron-density topology analysis (NCI region analysis, QTAIM theory) confirmed the closed-shell, non-covalent and attractive characters of the interaction between the Rh-I center and the proximal Cr(CO)(3) moiety. This study shows that, by appropriate tuning of the electronic properties of the ambiphilic ligand, truly coordination-unsaturated Rh-I complexes can be synthesized in a manageable form.