Di‐ and Tetranuclear Palladium(II) Complexes Containing C,N‐Bidentate Furoylhydrazone for Suzuki–Miyaura Reactions

Abstract

Furoylhydrazones of general formula 4‐R–C6H4–CH=NNH–CO–2‐C4H3O [R = H (HL1) and OCH3 (HL2)] have been conveniently prepared from furan‐2‐carbohydrazide. The reaction of HL1 with Li2[PdCl4] and CH3COONa provided the di‐µ‐chloro‐bridged cyclopalladated complex [Pd(C6H4–CH=N–NH–CO–2‐C4H3O)(µ‐Cl)]2 (1) through aryl C–H bond activation, whereas the unusual tetranuclear cluster [Pd(4‐CH3O–C6H4–CH=N–NH–CO–2‐C4H3O)(µ‐Cl)]4 (2) was obtained from the reaction with ligand HL2. The crystal structures of 1 and 2 show a slightly distorted square‐planar coordination geometry around the palladium ion to which the furoylhydrazone is attached in a bidentate fashion. The two palladium(II) complexes were able to catalyze the Suzuki–Miyaura coupling reactions of phenylboronic acid with aryl halides to afford the desired biaryl derivatives in excellent yields (up to 99.2 %).