Heteropolymetallic Complexes Linked to a 9,10-Dihydroanthracenyl Frame. Ruthenium as Active Spectator for Palladium Reactivity

New
monometallic Pd­(II) (3, 4) and heteropolymetallic
Pd­(II)/Ru­(II) complexes (5, 6) linked to
an original 9,10-dihydroanthracenyl–pyrrolidine scaffold were
synthesized and fully characterized. For monometallic complexes, exo-3 and endo-4 conformers were exclusively obtained from Pd­(OAc)2 and
[PdCl2(COD)], respectively. The formation of the sterically
hindered endo-4 was justified by the
positive noncovalent intramolecular Cl−π interaction,
observed by X-ray diffraction. The reaction of endo-4 with 1 and 2 equiv of [RuCp­(NCMe)3]­PF6 led to complexes 5 and 6, respectively.
It is worth noting that lower conversions in the Suzuki–Miyaura
coupling were found using 5 and 6 as catalysts,
in comparison to those with monometallic palladium complexes. This
behavior could be related to the higher stabilization of Pd­(II) species
for the heteropolymetallic complexes, as proven by electrochemical
analyses.