Chelating bis-N-heterocyclic carbene complexes of iron(II) containing bipyridyl ligands as catalyst precursors for oxidation of alcohols

Mara F. Pinto, Bernardo De P Cardoso, Sónia Barroso, Ana M. Martins, Beatriz Royo Cantabrana

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Abstract

Chelating bis-N-heterocyclic carbene (bis-NHC) complexes of iron(ii) containing pyridyl ligands have been prepared by the reaction of [FeCl2L] [L = bipy (1), phen (2)] with [LiN(SiMe3)2] and a bis(imidazolium) salt. The [Fe(bis-NHC)L(I)2] complexes were active pre-catalysts in the oxidation of 1-phenylethanol with tert-butyl hydroperoxide in neat conditions, affording a quantitative yield of acetophenone in 4.5 h. The catalyst could be reused up to six cycles giving a turnover number (TON) of 1500. Various secondary alcohols, both aromatic and aliphatic were selectivity oxidised to the corresponding ketones in excellent yields. Compound 1 is stable in acetonitrile solution for ca. 4 h, although after 16 h, it evolves to a mixture of [Fe(bis-NHC)(bipy)2]I2 (3), [Fe(bipy)3]2+ and bis-imidazolium salt. The molecular structure of 3 has been determined by X-ray diffraction studies.

Original languageEnglish
Pages (from-to)13541-13546
Number of pages6
JournalDalton Transactions
Volume45
Issue number34
DOIs
Publication statusPublished - 2016

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