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Immobilization of [Pd{(Ph 2 P) 2 N(CH 2 ) 3 Si(OCH 3 ) 3 ‐κ P,P '}X 2 ] (X=Cl, Br) onto Montmorillonite: Investigating their Performance as Homogeneous or Heterogenized Suzuki‐Miyaura Catalysts
Author(s) -
Stamatopoulos Ioannis,
Roulia Maria,
Vallianatou Kalliopi A.,
Raptopoulou Catherine P.,
Psycharis Vassilis,
Carravetta Marina,
Papachristodoulou Christina,
HeyHawkins Evamarie,
Kostas Ioannis D.,
Kyritsis Panayotis
Publication year - 2017
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201702601
Subject(s) - palladium , phenylboronic acid , chemistry , moiety , aryl , catalysis , chelation , crystallography , scanning electron microscope , ligand (biochemistry) , suzuki reaction , coupling reaction , electron paramagnetic resonance , nuclear chemistry , medicinal chemistry , stereochemistry , inorganic chemistry , materials science , organic chemistry , nuclear magnetic resonance , alkyl , composite material , biochemistry , receptor , physics
Two palladium complexes, [Pd{(Ph 2 P) 2 N(CH 2 ) 3 Si(OCH 3 ) 3 ‐κ 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 PdP 2 X 2 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 31 P 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.