Against All Odds, Uranium and Thorium Iminato Complexes Enable the Cleavage of C═O Bonds in Isocyanates

Konstantin Makarov, Ida Ritacco, Natalia Fridman, Lucia Caporaso*, Moris S. Eisen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

The catalytic activity of actinide-based catalysts is presented herein for the hydroboration and deoxygenation of isocyanates with pinacolborane (HBpin). A modified class of ligand systems possessing a five-membered ring core constructing the N-heterocyclic iminato moiety is introduced. All actinide complexes showed very good catalytic activities under mild conditions, with low catalyst loadings achieving almost quantitative yields. A wide number of isocyanates were studied including aliphatic isocyanates, aromatic isocyanates, and diisocyanates yielding to the corresponding borylated N-methyl amines and the borylated formamides, which are easily hydrolyzed toward the free amines and formamides. These organoactinide catalysts exhibited a great functional group tolerance toward methoxy, amido, and halides. The reaction selectivity was thoroughly investigated and exhibited a very good selectivity toward the isocyanate functionality having double or triple unsaturated C-C bonds. Kinetic studies were performed in order to establish the rate order dependency on the concentrations of the organoactinide complex, HBpin, and isocyanate. A proposed mechanism is presented based on experiments affording a more comprehensive understanding of the experimental activity trends and reinforced by the stoichiometric reaction studies, thermodynamic measurements, deuterium-labeling experiments, and theoretical DFT calculations.

Original languageEnglish
Pages (from-to)11798-11814
Number of pages17
JournalACS Catalysis
Volume13
Issue number17
DOIs
StatePublished - 1 Sep 2023

Keywords

  • C═O bond cleavage
  • N-heterocyclic imine
  • actinides
  • homogeneous catalysis
  • isocyanate hydroboration

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