Piano‐stool Ru (II) arene complexes that contain ethylenediamine and application in alpha‐alkylation reaction of ketones with alcohols

Abstract

A series of piano‐stool Ru (II) complexes (Ru1–7) bearing ethylenediamine with aryl and aliphatic groups were prepared and fully characterized by 1H, 13C, 19F and 31P NMR spectroscopy, FT‐IR and elemental analysis. The crystal structures of Ru2–4 and Ru7 were determined by X‐ray crystallography. They were successfully applied to the alpha(α)‐alkylation of aliphatic and aromatic ketones with alcohols via the borrowing hydrogen strategy in mild reaction conditions within a short time. The catalytic system has a broad substrate scope, which allows the synthesis of alpha alkylated ketones with excellent yields. The electronic and steric effects of complexes on catalytic activity were analysed. The influence of the carbon chain length of the ligand on the alpha‐alkylation reaction of ketones was also investigated. The catalytic cycle was also examined by 1H‐NMR spectroscopy in d8‐toluene.