Donor Functionalized Iron(II) N-Heterocyclic Carbene Complexes in Transfer Hydrogenation Reactions

Rita Lopes, Álvaro Raya-Barón, M. Paula Robalo, Carolina Vinagreiro, Sónia Barroso, Maria J. Romão, Ignacio Fernández, Mariette M. Pereira, Beatriz Royo

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Two piano-stool iron(II) complexes bearing N-heterocyclic carbene ligands outfitted with acetamide- and amine-pendant arms [Cp*Fe(NHCR)(CO)I] {Cp* = η5-tetramethylcyclopentadienyl; R = CH2CONEt2 (3), (CH2)2NEt2 (4)}, have been prepared and fully characterized. Their catalytic activity in transfer hydrogenation (TH) of ketones using iPrOH as a hydrogen source and catalytic amounts of base (LiOtBu) has been explored, along with that of previously reported [CpFe(NHCR)(CO)I] {R = nBu (5), (CH2)2OH (6), Et (7), and (CH2)3OH (8)} complexes containing hydroxyl and nonfunctionalized alkyl arms. Complex 3 displayed the highest catalytic activity of the whole series 3–8, reaching a TOF50 value of 533 h1. NMR monitoring of the stoichiometric reaction of 3 with LiOtBu, allowed the identification of a new species 3' containing a deprotonated amidate moiety, which has been fully characterized by 1H, 13C, and 15N NMR. Finally, a green protocol for the reduction of ketones through TH using glycerol as a hydrogen source, under microwave irradiation in the presence of catalytic amounts of 3 and base has been developed.

Original languageEnglish
Pages (from-to)22-29
Number of pages8
JournalEuropean Journal of Inorganic Chemistry
Volume2021
Issue number1
DOIs
Publication statusPublished - 8 Jan 2021

Keywords

  • Carbene ligands
  • Iron
  • Ketones
  • Microwave irradiation
  • Reduction
  • Transfer hydrogenation

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