Trans Ruthenium(II) Complexes with NH-Bridged Tetradentate Symmetric and Asymmetric Polypyridyl Ligands

NH-Bridged tetradentate ligands were synthesized to achieve stable
trans Ru(II) bis(polypyridyl) complexes. The polypyridyl part of the
ligand was either symmetric, as in N,N-bis(1,10-phenanthroline-2-yl)amine (phen-NH-phen), or asymmetric, as in N-(1,10-phenanthroline-2-yl)-N-(6-yl-dipyridyl[2,3-a:2‘,3‘-c]phenazine)amine (dppz-NH-phen). Protonation of phen-NH-phen with trifluoroacetic acid
and the subsequent reaction with RuCl3 yield trans-[Ru(phen-NH-phen)Cl2]. The chloro ligands in this compound can easily be
replaced by stronger ligands, such as CH3CN and DMSO. In this
way, complexes trans-[Ru(phen-NH-phen)(CH3CN)(DMSO)](PF6)2
(1), trans-[Ru(phen-NH-phen)(DMSO)2](PF6)2 (2), and trans-[Ru(phen-NH-phen)(CH3CN)2](PF6)2 (3) were obtained. X-ray structures
were determined for 1 and 3. Following a procedure similar to
that used with phen-NH-phen, the complex trans-[Ru(dppz-NH-phen)(CH3CN)2](PF6)2 (4) was obtained. To our knowledge, this
is the first reported trans ruthenium(II) bis(polypyridyl) complex
with two different polypyridyl ligands in the equatorial plane.