Studies on Aerobic Reactions of Ammonia/3,5-Di-terf-butylcatechol Schiff-Base Condensation Products with Copper, Copper(I), and Copper(II). Strong Copper(II)-Radical Ferromagnetic Exchange and Observations on a Unique N-N Coupling Reaction

Gabor Speier, Jozsef Csihony, Anne M. Whalen, Cortlandt G. Pierpont

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Abstract

Stoichiometric quantities of 3,5-di-tert-butylcatechol and aqueous ammonia react in pyridine solution to form 2-amino-4,6-di-tert-butylphenol. Under an atmosphere of dioxygen the aminophenol is oxidized to either the corresponding iminosemiquinone or iminobenzoquinone. In the presence of Cu(II) iminosemiquinone condensation with the aminophenol gives the Cat-N-SQ radical ligand obtained as the Cu(py)2(Cat-N-SQ) complex. Metal and ligand magnetic orbitals are orthogonal and couple ferromagnetically to give a S = 1 molecular spin state at temperatures up to 300 K. In nonpolar solvents the complex undergoes ligand oxidation and disproportionation to give Cu(Cat-N-BQ)2. Csrystallographic characterization on crystals obtained as the i-propanol solvate [orthorhombic, C2221, a = 19.548(3) Å, b = 24.536(5) Å, c = 23.655(5) Å,V = 11346(4) Å3, Z = 8, A = 0.068] show that the expected Jahn-Teller distortion appears in the trans Cu-O lengths of the equatorial plane rather than for the axial Cu-N lengths. Reactions carried out with both Cu(I) and Cu metal require metal oxidation to give the Cu(II) products obtained. With metallic Cu this occurs by a reaction with iminoquinone to give bis-(iminosemiquinone)copper(II). Further reaction of this product with aminophenol gives Cu(py)2(Cat-N-SQ) by condensation, and, with O2, oxidation gives a coordinated azophenolate ligand in Cu(py)(azophenolate) by a unique N-N bond-forming reaction. Cu(py)(azophenolate) has been characterized crystallographically [monoclinic, P21/n, a = 10.990(2) Å, b = 10.736(3) Å, c = 26.848(4) Å, β = 98.09(1)°, V = 3136(1) Å33, Z = 4, R = 0.048].

Original languageEnglish
Pages (from-to)3519-3524
Number of pages6
JournalInorganic Chemistry
Volume35
Issue number12
Publication statusPublished - Dec 1 1996

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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