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

摘要

abstract_textpTwo palladium complexes, Pd{(Ph2P)(2)N(CH2)(3)Si(OCH3)(3)-P,P'}X-2, 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)degrees, 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 degrees C, using 0.1mol of palladium loading, high conversions were observed even after 15min. 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 (PNMR)-P-31 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./p/abstract_text