Applications of transition metal complexes containing aminophosphine ligand to transfer hydrogenation of ketones

Article abstract of DOI:10.1002/aoc.1753

Hydrogen transfer reduction processes are attracting increasing interest from synthetic chemists in view of their operational simplicity. Reaction of [Ph₂PNHCH₂-C₄H₃S] with [Ru(ν⁶-benzene)(μ-Cl)Cl]₂, [Rh(μ-Cl)(cod)] ₂ and [Ir(ν⁵-C₅Me₅)(μ-Cl)Cl] ₂ gave a range of new monodendate complexes [Ru(Ph ₂PNHCH₂-C₄H₃S)(ν⁶- benzene)Cl₂], 1, [Rh(Ph₂PNHCH₂-C ₄H₃S)(cod)Cl], 2, and [Ir(Ph₂PNHCH ₂-C₄H₃S)(ν⁵-C₅Me ₅)Cl₂], 3, respectively. All new complexes were fully characterized by analytical and spectroscopic methods. ¹H- ³¹P NMR, ¹H-¹³C HETCOR or ¹H- ¹H COSY correlation experiments were used to confirm the spectral assignments. 1-3 are suitable catalyst precursors for the transfer hydrogenation of acetophenone derivatives. Notably [Ru(Ph₂PNHCH₂-C ₄H₃S)(ν⁶-benzene)Cl₂], 1, acts as an excellent catalyst, giving the corresponding alcohols in 98-99% yields in 30 min at 82 °C (TOF a200 h;bsupesup) for the transfer hydrogenation reaction in comparison to analogous rhodium or iridium complexes. This transfer hydrogenation is characterized by low reversibility under these conditions.