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Intrazeolite chemistry of nickel(0) complexes and Ni(0,II) clusters studied by EXAFS, solid-state NMR and FT-IR spectroscopy

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  • Chemie Und Pharmazie
  • Ddc:540


J . Am. Chem. SOC. 1988, JJO, 1801-1810 1801 Intrazeolite Chemistry of Nickel( 0) Complexes and Ni( 0,II) Clusters Studied by EXAFS, Solid-state NMR, and FT-IR Spectroscopy Thomas Bein,*"vb Stephan J. McLain,*'* David R. Corbin," Rodney D. Farlee,'& Karin Moller,laYb Galen D. Stucky,la*c Geoffrey Woolery,*ld and Dale Sayersle Contribution from the Central Research and Development Department.' E. I . du Pont de Nemours and Company, Experimental Station, Wilmington, Delaware 19898, the Paulsboro Research Laboratory, Mobil Research and Development Corporation, Paulsboro, New Jersey 08066. and the Department of Physics, North Carolina State University, Raleigh, North Carolina 27695. Received March 3, 1987 Abstract: Adsorption, thermal decomposition, and reactivity of Ni(CO), in the cage system of dehydrated zeolite Y has been studied with EXAFS and near-edge spectroscopies, in particular monitoring changes in oxidation states and Ni ligation. Ni(CO), is adsorbed as an intact molecule in cation-free zeolite Y, LiY, and Nay. Symmetry changes of the molecule in LiY and NaY are assigned to the formation of cation-OC-Ni bridges. Thermal treatment of the Ni(CO),/NaY adduct leads to loss of CO concomitant with the formation of a bimodal Ni phase. A major part of the Ni forms small clusters (approximately 0.5 to 1.5 nm), in addition to larger crystallites (5-30 nm), sticking at the outer surface of the zeolite crystals. Oxidation of Ni(CO),/NaY to NiO/NaY with molecular oxygen occurs almost to completion below 295 K. The small NiO particles are stable to sintering up to 670 K. Nickel-phosphine/NaY adducts have been prepared by direct adsorption from solution [Ni(CO)3PMe3, Ni(C0)2(PMe3)2], and by synthesis inside the NaY supercage [Ni(CO)3PMe3, Ni(CO),(PPh,CHMe,), Ni (co) ,P( t -B~)~, Ni(PMe,),]. The NaY/Ni(CO)3(PPh2CHMe2) adduct is a ship-in-a-bottle complex, Le., the Ni complex is too large to exit the zeolite supercage. The substitution of carbonyl ligands by phosphines

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