Inorg. Chem. 2008, 47, 6121-6123
Oxidative CsH and CsC Bond Cleavage by a (2,2′-Bipyridine)Copper(I)
Chloride Complex
Ro´bert Csonka,† Jo´zsef Kaizer,† Michel Giorgi,‡ Marius Re´glier,‡ La´szlo´ Hajba,§ Ja´nos Mink,|,⊥
and Ga´bor Speier*,†
Department of Chemistry, UniVersity of Pannonia, H-8200 Veszpre´m, Hungary, Spectropoˆle-RX,
UniVersite´ Paul Ce´zanne Aix-Marseille III, F. S. T. Saint-Je´roˆme, SerVice D11, AVenue Escadrille
Normandie-Niemen, 13397 Marseille cedex 20, France, Department of Earth and EnVironmental
Sciences, UniVersity of Pannonia, H-8200 Veszpre´m, Hungary, Chemical Research Center of the
Hungarian Academy of Sciences, H-1025 Budapest, Hungary, and Faculty of Information
Technology, Research Institute of Chemical and Process Engineering, UniVersity of Pannonia,
H-8200 Veszpre´m, Hungary
Scheme 1. The Formation of Complex 1
Acetonitrile is easily oxygenated at ambient reaction conditions to
copper(II) oxalate [Cu(bpy)(ox)]n mediated by copper(I) chloride
in the presence of 3,5-di-tert-butylcatechol and 2,2′-bipyridine. In
the case of other nitriles (e.g., propionitrile), instead, the unusual
and selective 1,4-extradiol cleavage of 3,5-di-tert-butylcatechol
occurs to give copper(II) tert-butylmaleate [Cu(bma)(bpy)(H2O)]n
in good yield.
Copper(I) chloride in the presence of amines constitutes
an efficient and also industrially important oxidizing/
oxygenating system with dioxygen.1 The stoichiometry of
the reaction of CuCl and amines with O2 is Cu/O2 ) 4:1,
leading to [CuCl(amine)]4O2.2 The industrially used oxidative
coupling of phenols to aromatic polyethers3 or dipheno-
quinone4 is an important process, and catalysts of this type
have biological importance too because they mimic tyrosi-
nase,5 catechol oxidase,6 and catechol dioxygenase.7
We and others have found previously that catechols can
be oxidized to o-quinones8 or cleaved to cis,cis-muconic
acids9 by dioxygen in the presence of copper catalysts. It is
also known that catechols can be aminated to give o-
aminophenols,10 and we looked for possible catalysts for this
reaction. During the course of these studies, we observed
surprisingly that the solvent acetonitrile used had been
oxygenated. When copper(I) chloride in the presence of 3,5-
di-tert-butylcatechol (dtbcH2) or 3,5-di-tert-butyl-1,2-ben-
zoquinone and 2,2′-bipyridine (bpy) in acetonitrile as the
solvent is reacted with dioxygen (Scheme 1), the pale-green
compound of [Cu(bpy)(ox)]n (1) (ox ) oxalate) is obtained
after recrystallization in 46% yield. Complex 1 is paramag-
netic, with electron paramagnetic resonance (EPR) param-
eters of g| ) 2.173 and g⊥) 2.070 at 77 K. The structure of
[Cu(bpy)(ox)]n was proved by spectroscopic data and X-ray
crystal structure determination (Figure 1), and the data found
were slightly different from those observed earlier.11 The
2,2′-bipyridine(µ-1,2,3,4-oxalato)copper complex is com-
posed of polymeric chains of [Cu(bpy)]2+ ions bridged by
* Author to whom correspondence should be addressed. E-mail: speier@
almos.vein.hu.
†
Department of Chemistry, University of Pannonia.
Universite´ Paul Ce´zanne Aix-Marseille III.
Department of Earth and Environmental Sciences, University of
‡
§
Pannonia.
|
Chemical Research Center of the Hungarian Academy of Sciences.
Research Institute of Chemical and Process Engineering, University
⊥
of Pannonia.
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10.1021/ic800745g CCC: $40.75 2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 14, 2008 6121
Published on Web 06/26/2008