Mononuclear ruthenium(II) complexes bearing the (S,S)-iPr-pybox ligand

The complexes trans-[RuCl2(L){(S,S)-iPr-pybox}] ((S,S)-iPr-pybox = 2,6-bis[4′-(S)-isopropyloxazolin-2′-yl]pyridine, L = PMe3 (1), P(OMe)3 (2), PPh2(CH2CHCH2) (3), CNBn (5), CNCy (6) and MeCN (7)) have been synthesized by substitution of ethylene on the precursor trans-[RuCl2(η2-C2H4){(S,S)-iPr-pybox}]. This complex also reacts with cyclooctadiene (cod) or norbornadiene (nbd) and NaPF6, in refluxing methanol, giving the coordination compounds [RuCl(η4-cod){(S,S)-iPr-pybox}][PF6] (8) and [RuCl(η4-nbd){(S,S)-iPr-pybox}][PF6] (9). The structures of complexes [RuCl(CO)(PPh3)(H-pybox)][BF4] (H-pybox = 2,6-bis(dihydrooxazolin-2′-yl)pyridine) (4), 6 and 8, have been resolved by X-ray diffraction methods. The catalytic activity of the new complexes in transfer hydrogenation of acetophenone has also been examined.

Graphical abstractThe synthesis and structural characterization of new ruthenium(II) complexes with potential catalytic activity is reported. The ready accessibility of the complexes [RuCl(η4-diene){(S,S)-iPr-pybox}][PF6] (diene = cod (8), nbd (9)) and trans-[RuCl2(MeCN){(S,S)-iPr-pybox}] (7) opens a way to study the potential of new ruthenium pybox complexes containing labile ligands in asymmetric catalysis.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Stereoselective synthesis of diolefin ruthenium(II) complexes. ► Asymmetric Catalysis. ► Enantiopure ruthenium(II)-pybox complexes with potential catalytic activity.