Schiff Bases of the BIAN Family : from Symmetrical Biaryl Derivatives to Mixed, Alkyl, Chiral or Reduced Ligands and Heterogeneous Catalysts
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Data di Pubblicazione:
2017
Citazione:
Schiff Bases of the BIAN Family : from Symmetrical Biaryl Derivatives to Mixed, Alkyl, Chiral or Reduced Ligands and Heterogeneous Catalysts / F. Ragaini. ((Intervento presentato al 26. convegno Congresso Nazionale della Società Chimica italiana-SCI tenutosi a Paestum nel 2017.
Abstract:
The number of applications of bis-imines as ligands in homogeneous catalysis has much increased in
recent years. Derivatives of acenaphthenequinone (R-BIANs) are especially useful to this purpose
because the rigidity of the acenaphthene skeleton strengthen coordination to a metal and add stability
against the rupture of the central C-C bond of the diimine moiety.
During the years, we have expanded the available range of Ar-BIANs to ligands where the aryl group
bears strongly electronwithdrawing substituents, two different aryl groups are present, and
first prepared usually unstable Alkyl-BIAN compounds.
The key principles which allowed these products to be
obtained will be illustrated. Solubility of the products and the
right control of ring strain for alkyl derivatives are essential
points.
The coordinating strength of a series of Ar-BIAN ligands to
several palladium complexes has been measured and varies
linearly with the log of Hammett constant. The slope of the
correlation depends on the metal complex and can be
regarded as measure of its Lewis acidity.
The family of R-BIAN ligands was then further expanded to
chiral derivatives and finally to reduced ligands, Ar-BIANH2. The latter
are air sensitive compounds, but are stable under in the solid state an inert atmosphere and can be
employed to synthesize catalytically active complexes without resorting to the use of reduced metal
precursors or alkaline-metal reduced intermediates
At the end of this evolution, the last application
was to decompose the coordinated ligand at
high temperatures to generate
heterogeneous nitrogen- enriched graphitic cobalt
catalysts, effective in hydrogenation reactions for
which traditional cobalt catalysts are inactive
Tipologia IRIS:
14 - Intervento a convegno non pubblicato
Elenco autori:
F. Ragaini
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