Alkane Oxidation by an Immobilized Nickel Complex Catalyst: Structural and Reactivity Differences Induced by Surface‐Ligand Density on Mesoporous Silica. Issue 6 (12th April 2013)

• Record Type: Journal Article
• Authors: Nakazawa, Jun; Hori, Tomoaki; Stack, T. Daniel P.; Hikichi, Shiro
• Is Part Of: Chemistry, an Asian journal. Volume 8:Issue 6(2013:Jun.)
• Page Start: 1191
• Page End: 1199
• Publication Date: 2013-04-12
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1002/asia.201300165
• Languages: English
• ISSNs: 1861-4728

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Immobilized nickel catalysts SBA*‐<bold>L</bold>‐<italic>x</italic>/Ni (<bold>L</bold>=bis(2‐pyridylmethyl)(1H‐1, 2, 3‐triazol‐4‐ylmethyl)amine) with various ligand densities (<bold>L</bold> content (<italic>x</italic>)=0.5, 1, 2, 4 mol % Si) have been prepared from azidopropyl‐functionalized mesoporous silicas SBA‐N<sub>3</sub>‐<italic>x</italic>. Related homogeneous ligand <xref ref-type="link" rid="sch2">2</xref> and its Ni<sup>II</sup> complexes, [Ni(<xref ref-type="link" rid="sch2">2</xref>)(OAc)<sub>2</sub>(H<sub>2</sub>O)] (<xref ref-type="link" rid="sch2">2</xref>/Ni) and [Ni(<xref ref-type="link" rid="sch2">2</xref>)<sub>2</sub>]BF<sub>4</sub> (2 <xref ref-type="link" rid="sch2">2</xref>/Ni), have been synthesized. The <bold>L</bold>/Ni ratio (0.9–1.7:1) in SBA*‐<bold>L</bold>‐<italic>x</italic>/Ni suggests the formation of an inert [Ni<bold>L</bold><sub>2</sub>] site on the surface at higher ligand loadings. SBA*‐<bold>L</bold>‐<italic>x</italic>/Ni has been applied to the catalytic oxidation of cyclohexane with <italic>m</italic>‐chloroperbenzoic acid (<italic>m</italic>CPBA). The catalyst with the lowest loading shows high activity in its initial use as the homogeneous <xref ref-type="link" rid="sch2">2</xref>/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.</p> </abstract>