Immobilization of [Pd{(Ph2P)2N(CH2)3Si(OCH3)3‐κP,P'}X2] (X=Cl, Br) onto Montmorillonite: Investigating their Performance as Homogeneous or Heterogenized Suzuki‐Miyaura Catalysts

Abstract

AbstractTwo palladium complexes, [Pd{(Ph2P)2N(CH2)3Si(OCH3)3‐κP,P'}X2], X=Cl (2), Br (3), were synthesized and characterized by spectroscopic methods and X‐ray crystallography. Complexes 2 and 3 contain a PdP2X2 square planar coordination sphere exhibiting small endocyclic P–Pd–P angles [71.49(4) and 71.53(5)°, respectively], the magnitude of which is controlled by the formation of the Pd–P–N–P four‐membered chelating ring. Complexes 2 and 3 were found to be efficient catalysts in the Suzuki‐Miyaura cross‐coupling reaction of aryl bromides with phenylboronic acid at ambient or elevated temperature. At 100 °C, using 0.1 mol% of palladium loading, high conversions were observed even after 15 min. Both complexes were immobilized onto STx‐1 montmorillonite clay via their −Si(OMe)3 moiety, a process investigated by X‐ray powder diffraction, X‐ray fluorescence spectrometry, solid‐state 31P NMR spectroscopy and Scanning Electron Microscopy. The immobilized complexes, as heterogenized catalysts, displayed higher activity in the Suzuki‐Miyaura coupling compared to that of the free complexes. The recyclability of the former was also explored.