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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 (Ru4 and Ru8) 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 5.7×106 h−1 TOFs. [ABSTRACT FROM AUTHOR]

Rhodium(iii)-catalyzed conjugate addition of aromatic and olefinic C–H bonds to CF3-substituted unsaturated ketones was efficiently achieved. Both arene and olefin substrates bearing a chelate assisted-directing group were coupled with a variety of β-trifluoromethyl-α,β-unsaturated ketones with excellent atom-economy, high yields, and broad substrate scopes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Highly active mono- and multinuclear Ru(II) complex catalysts. • Applied in various borrowing hydrogen strategy reations. • Low catalyst loading for TH reaction (0.005-0.2 mol% Ru). Various pincer-type ruthenium(II) complexes were developed from our laboratories and herein the relevant advance is summarized from a viewpoint of their synthesis and organic synthetic applications as homogeneous catalysts. The investigated Ru(II)–NNN and Ru(II)–NNNN-type complexes exhibited highly catalytic activities in the transfer hydrogenation of ketones, C–C bond formation from alcohols and ketones, and dehydrogenation. RuH complexes were identified or considered as the catalytically active intermediates for these transformations. This review deals with the following subjects: (i) mononuclear ruthenium(II) pincer complexes with high catalytic activity in (asymmetric) transfer hydrogenation of ketones; (ii) multinuclear ruthenium(II) complexes for transfer hydrogenation of ketones; (iii) mononuclear ruthenium(II) complexes for other reactions such as Oppenauer-type oxidation, β -alkylation of secondary alcohols, synthesis of multisubstituted heterocycles, acceptorless dehydrogenation of N -heterocycles and secondary alcohols. [ABSTRACT FROM AUTHOR]