Ruthenium (II) thiacrown complexes as hydrogen-transfer reduction catalysts

An investigation into the potential of a series of Ruthenium (II) thiacrown complexes with general formula [Ru([9]aneS3)Cl2(L)] and [Ru([n]aneS4)Cl(L)]+, where L = DMSO or Ph3P, n = 12, 14, or 16, as hydrogen transfer reduction catalysts is reported. As part of these studies two new complexes incorporating [Ru([12]aneS4)] and [Ru([16]aneS4)] metal centres have been synthesised and fully characterised. The X-ray structure of one of these complexes is also reported. The UV/Vis spectra of these complexes are dominated by π → π* transitions, with weaker d → d transitions also being apparent. Using these eight structurally related complexes, studies on the transfer hydrogenation of acetophenone using propan-2-ol as the hydride source were carried out. This work revealed that the complexes displayed catalytic activity in the presence of a base promoter. Although the activity of these complexes were considerably lower than that of structurally related mixed-donor ligand systems, there was some evidence that the flexibility of the ligand did have an effect on initial catalytic activity.

Graphical abstractA series of ruthenium(II) complexes of thiacrown ligands, including two new systems incorporating [Ru([12]aneS4)] and [Ru([16]aneS4)] metal centres, have been investigated as possible hydrogen transfer reduction catalysts. It has been found that the complexes do display catalytic activity in the presence of a base promoter.Figure optionsDownload full-size imageDownload as PowerPoint slide