Cationic and neutral ruthenium(II) complexes containing both arene or Cp* and functionalized aminophosphines. Application to hydrogenation of aromatic ketones

Hydrogen transfer reduction processes are attracting increasing interest from synthetic chemists in view of their operational simplicity. For this aim, a series of novel Ru(II) complexes with the P-N-P ligands were synthesized starting from the complex [Ru(eta 6-p-cymene)(mu-Cl) Cl] 2 or [RuCp*Cl(COD)]. The complexes were fully characterized by analytical and spectroscopic methods. (31)P-{(1)H} NMR, DEPT, (1)H-(13)C HETCOR or (1)H-(1)H COSY correlation experiments were used to confirm the spectral assignments. Complexes 5, 6 and 7 catalyze the transfer hydrogenation of acetophenone derivatives to 1-phenylethanol derivatives in the presence of iso-PrOH as the hydrogen source. Catalytic studies showed that all complexes are excellent catalytic precursors for the transfer hydrogenation of acetophenone derivatives in 0.1 M iso-PrOH solution. Notably 5 acts as an excellent catalyst giving the corresponding alcohols in excellent conversions up to 99% (TOF <= 492 h(-1)). (C) 2010 Elsevier B. V. All rights reserved.