Synthesis, structure and redox properties of ruthenium complexes containing the tpm facial and the trpy meridional tridentate ligands

Ruthenium polypyridyl complexes containing the bischelating ligand 2,2′-azobispyridine. Synthesis, characterization and crystal structures

“…The X-ray structures of the three newly prepared complexes are presented, which provide interesting observations by comparison with each other, as well as with other already reported related structures [10,11,13,14]. These results indicate a powerful possibility to tune the sixth coordination site and tailor-make complexes that display varying properties, thereby fulfilling different requirements.…”

“…The terpy ligand is coordinated in such a way that the distance between the ruthenium and the central N is shorter than the distances between the ruthenium and the extreme N atoms. This characteristic was also observed in the above-mentioned azpy analogues [10,11,13], whereas in the starting complex Ru(tpy)Cl 3 these three bond lengths are equivalent [14]. Finally the terpy ligand is planar whereas the apy ligand is not.…”

Synthesis and structural characterization of some polypyridyl and polypyrazolyl Ru(II) complexes

“…In addition, if the complex were the other isomer there would seem to be no reason why the third pyrazolyl group of the second tpm ligand should not coordinate during the ligand exchange chemistry described below. The same complex, 3, was isolated when either RuCl 3 These results clearly show that while it is possible to remove the chloride ligand, this only occurs if there is a suitable ligand to replace it. The pendant pyrazolyl group does not coordinate.…”

“…Bond lengths and bond angles (Table 1) are within the range found for similar structures previously described in the literature. 3,47,48 The bond length to the pyrazolyl donor that is trans to the monodentate ligand is shorter than those to the other two donors in both complexes. This may be due to the relative trans influences of the non-tpm ligands in these complexes.…”

“…If a facial tridentate ligand is attached to a metal centre, the remaining three coordination sites on an octahedral metal centre must also be disposed in a facial manner. In principle, therefore, the known compound [Ru(tpm)Cl 3 ] 2,3 should be restricted to the tpm binding site of the ditopic ligand, if it is to replace all three chloride ligands with heterocyclic donors. On the other hand, a ttp complex, [Ru(ttp)Cl 3 ] 4 , might be expected to bind to the terpyridyl binding site.…”