Assembled Porphyrin‐Based Multinuclear Ruthenium(II)‐NNNN Complex Catalysts for Transfer Hydrogenation of Ketones

Abstract

Multinuclear porphyrin-based ruthenium(II)-NNNN complexes were efficiently assembled by means of coordinatively unsaturated 16-electron mononuclear ruthenium(II)-pyrazolyl-imidazolyl-pyridine complex, zinc(II) meso-tetra(4-pyridyl)-porphyrin (ZnTPyP), and 4,4'-linked bipyridines. The resultant multinuclear (Ru 4 and Ru 8 ) porphyrin-based ruthenium(II)-NNNN complexes exhibited exceptionally high catalytic activity at as low as 0.008 mol % Ru loading for the transfer hydrogenation reaction of ketones in refluxing 2-propanol, reaching up to 99 % yields and 5.7 × 10 6 h À 1 TOFs.