N,N,N′,N′-Tetrakis(2-hydroxyethyl)ethylenediamine palladium(II) complex as efficient catalyst for the Suzuki/Miyaura reaction in water

A new water soluble palladium(II) complex (2) derived from N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine (edteH4) (1) was synthesized in high yield and characterized by 1H, 13C, HMQC and COSY NMR spectroscopy. X-ray diffraction studies on a single crystal of 2 confirmed the cis square planar geometry; the edteH4 ligand (1) is κ2 (N,N)-coordinated with four pendant CH2CH2OH groups. This new complex [PdCl2(edteH4)] (2) and the previously synthesized triethanolamine complex [Pd(OCH2CH2N(CH2CH2OH)2)2] (3) were tested as catalysts for the Suzuki/Miyaura cross-coupling reaction of various aryl bromides with phenylboronic acid in water. Electronically activated aryl bromides, such as 4-bromoacetophenone and 4-bromobenzaldehyde undergo the cross-coupling with extremely high turnover numbers (TON) of up to 1,00,000 without organic solvent.