Cyclometalated ruthenium(II) complexes of benzo[h]quinoline (bzqH)[Ru(bzq)(NCMe)4]+, [Ru(bzq)(LL)(NCMe)2]+, and [Ru(bzq)(LL)2]+ (LL=bpy, phen)

Reductive Labilization of a Cyclometalating Ligand Applied to Auxiliary-Mediated Asymmetric Coordination Chemistry

“…The ligand added at first (phen) occupies the sterically less hindered coordination sites, and the second phenanthroline (tmphen) slips under the isopropyl group. This spatial ligand arrangement is in accordance with results previously found for a ruthenium bis­(polypyridyl) complex bearing a structurally related S -configured salicyloxazolinato ligand. , The Ru–N bond trans to the Ru–C bond is almost 0.1 Å (average) longer in comparison to the other Ru–N bonds, due to the distinct structural trans effect. ,, …”

“…For the methyl protons H e of the second MeCN ligand only a single coupling to the proton H f in a position α to the ligating carbon donor of the phenylic ligand backbone is visible. Taken together, the interpretation of these NOE contacts results in a defined ligand arrangement around the ruthenium center and the relative intensities of the cross-peaks in the NOE experiment correlate with the calculated interatomic distances, thus supporting the suggested structure Δ-(S)-4 (Figure4): one nitrogen atom of phen coordinates trans to the cyclometalating carbon donor,15,18,20,21 the other nitrogen occupies a position that ensures a minimal steric hindrance with the demanding isopropyl moiety, therefore pointing the farthest away from this group, and the MeCN ligands are located cis to each other. This pictured ligand arrangement constitutes a Δ configuration at the metal center.Our findings regarding the metal-centered Δ configuration of the intermediate Δ-(S)-4 combined with the assigned Λ configuration for the bis(phenanthroline) diastereomer Λ-(S)-3 reveal a Δ → Λ isomerization upon substitution of the last two remaining MeCN ligands of the intermediate Δ-(S)-4 with the second phen to afford Λ-(S)-3.…”

“…5a,b The Ru−N bond trans to the Ru−C bond is almost 0.1 Å (average) longer in comparison to the other Ru−N bonds, due to the distinct structural trans effect. 20,21,24 Mechanistic Considerations for the Diastereoselective Coordination Chemistry. A comparison of the ligand arrangement in intermediate Δ-(S)-4 and the diastereomer Λ-(S)-7 reveals that the binding position of the first added phen ligand changes in the course of the coordination of the second bidentate ligand.…”

Synthesis and X-ray Studies of Novel Azaphenanthrenes

“…10 Additionally, cyclometalated ruthenium(II) complexes of benzo[h]quinoline were described as mediators in the electron exchange for the reduced active site of glucose oxidase (oxidation of β-D-glucopyranose into the corresponding γ-lactone) from Aspergillus niger. 11 Interest in construction of the present targets is also due to the smooth muscle relaxant properties of nicotinonitrile-containing compounds useful as vasodilators and bronchodilators. 12 Vasodilators are antihypertensive drugs accessible for smooth muscle relaxation to lower arterial pressure.…”