Activation of aldehydes by exocyclic iridium(I)-eta(4):pi(2)-diene complexes derived from 1,3-oxazolidin-2-ones

摘要

The Ir(I) complexes [Tp(Me2)Ir(eta(4)-1,4-diene)] 2b and 2c react thermally with a variety of aromatic aldehydes, 3a-e, to generate the metallabicyclic compounds 4e-k and the Fischer-type carbenes 5a-b in moderate yields. These reactions are proposed to take place with the initial formation of eta(1)-aldehyde adducts as key intermediates. The formation of the metallabicyclic compounds 4e-k involves a formal decarboxylation process at the exo-2-oxazolidinone diene and an ortho metallation of the aromatic ring. The generation of the Fischer-type carbenes 5a-b is the result of a series of metal-based rearranged intermediates with no decarboxylation observed. Treatment of the eta(4)-diene complex 2b with a variety of Lewis bases induces a change in the binding mode of the diene ligand from eta(4):pi(2) to eta(2):sigma(2) to form the Ir(III) derivatives 6b-d of composition Tp(Me2)Ir-(eta(4):pi(2)-1,4-diene)(L) (L = CO, MeCN, and C5H5N). A study of reactions of complex 2b with either mono-or poly-deuterated aldehydes was performed to understand the mechanisms of such processes. The results of these studies were used to determine plausible formation mechanisms of the metallabicyclic compounds 4e-4k and Fischer-type carbenes 5a-b compound series. These mechanisms were corroborated by density functional theory (DFT) calculations of the free energy profiles.