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Alkane Oxidation by an Immobilized Nickel Complex Catalyst: Structural and Reactivity Differences Induced by Surface‐Ligand Density on Mesoporous Silica
Author(s) -
Nakazawa Jun,
Hori Tomoaki,
Stack T. Daniel P.,
Hikichi Shiro
Publication year - 2013
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201300165
Subject(s) - catalysis , nickel , cyclohexane , ligand (biochemistry) , mesoporous silica , mesoporous material , alkane , leaching (pedology) , metal , chemistry , mcm 41 , reactivity (psychology) , inorganic chemistry , nuclear chemistry , organic chemistry , medicine , biochemistry , receptor , environmental science , alternative medicine , pathology , soil science , soil water
Immobilized nickel catalysts SBA*‐ L ‐ x /Ni ( L =bis(2‐pyridylmethyl)(1H‐1,2,3‐triazol‐4‐ylmethyl)amine) with various ligand densities ( L content ( x )=0.5, 1, 2, 4 mol % Si) have been prepared from azidopropyl‐functionalized mesoporous silicas SBA‐N 3 ‐ x . Related homogeneous ligand LtBu and its Ni II complexes, [Ni( LtBu )(OAc) 2 (H 2 O)] ( LtBu /Ni) and [Ni( LtBu ) 2 ]BF 4 (2 LtBu /Ni), have been synthesized. The L /Ni ratio (0.9–1.7:1) in SBA*‐ L ‐ x /Ni suggests the formation of an inert [Ni L 2 ] site on the surface at higher ligand loadings. SBA*‐ L ‐ x /Ni has been applied to the catalytic oxidation of cyclohexane with m ‐chloroperbenzoic acid ( m CPBA). The catalyst with the lowest loading shows high activity in its initial use as the homogeneous LtBu /Ni catalyst, with some metal leaching. As the ligand loading increases, the activity and Ni leaching are suppressed. The importance of site‐density control for the development of immobilized catalysts has been demonstrated.