Zinc(ll)-Templated Synthesis of a [2]-Catenane Consisting of a 2,26,2-Terpyridine-lncorporatmg Cycle and a 1,10-Phenanthroline-Containing Ring

A nonsymmetrical [2]-Catenane has been synthesized, with a 5-coordinated metal center (Zn2+) as template. One of the two rings contains a terdentate ligand (2,2ʹ,6ʹ,2"-terpyridine) and the other one incorporates a bidentate chelate (1,10-phenanthroline). The first ring was prepared separately and, subsequently, Zn^2+ was used as the gathering and threading element to pass the stringlike component through the ring. This open-chain species bears two terminal olefins, which were reacted with Grubbs first-generation catalyst (ring-closing metathesis) to afford the desired catenane. Hydrogenation of the double bond and removal of the zinc(ll) template afforded the final free [2]-Catenane in 40% yield from the terdentate ligand-containing cycle and the diolefinic compound. Complexation studies on this new pentacoordinating catenane were carried out with Fe(ll) or Cu(ll). The most interesting observation is that the 5-coordinated complexes obtained are strongly stabilized. Their electrochemical reduction occurs at negative potentials.