An Electron‐Deficient Cp^E Iridium(III) Catalyst: Synthesis, Characterization, and Application to Ether‐Directed C−H Amidation

Abstract

The synthesis, characterization, and catalytic performance of an iridium(III) catalyst with an electron‐deficient cyclopentadienyl ligand ([CpEIrI2]2) are reported. The [CpEIrI2]2 catalyst was synthesized by complexation of a precursor of the CpE ligand with [Ir(cod)OAc]2, followed by oxidation, desilylation, and removal of the COD ligand. The electron‐deficient [CpEIrI2]2 catalyst enabled C−H amidation reactions assisted by a weakly coordinating ether directing group. Experimental mechanistic studies and DFT calculations suggested that the high catalytic performance of [CpEIrI2]2 is due to its electron‐deficient nature, which accelerates both C−H activation and IrV‐nitrenoid formation.

Phosphonium‐substituted Diphosphaindenylide (PPI): Exploration of Biradical Character and Ligand Properties

“…This electron deficiency has proven advantageous for catalytic transformations of electron-rich substrates. [9][10][11] Therefore, the utilization of even more electron-deficient, zwitterionic indenylide ligands holds great potential for further enhancing the activation of electron-rich substrates, by combining the indenyl effect with electron-poor, Lewis-acidic metal centers.…”

“…It has been found that already the addition of neutral electron‐withdrawing groups to [C 5 H 5 ] − renders the resulting metal complexes rather electron‐deficient. This electron deficiency has proven advantageous for catalytic transformations of electron‐rich substrates [9–11] . Therefore, the utilization of even more electron‐deficient, zwitterionic indenylide ligands holds great potential for further enhancing the activation of electron‐rich substrates, by combining the indenyl effect with electron‐poor, Lewis‐acidic metal centers.…”

Rhodium complexes with planar-chiral cyclopentadienyl ligands: synthesis from tert-butylacetylene and catalytic performance in C–H activation of arylhydroxamates

“…For example, Shibata and Tanaka have reported the preparation of complex 1 with electron acceptor cyclopentadienyl ligand C 5 Me 3 (COOEt) 2 from ethyl butynoate and triisopropylsilyl-acetylene. 6,7 More recently, we have shown that rhodium complexes 2 and 3 can be obtained by tri-or tet-ramerization of the tert-butylacetylene directly in the coordination sphere of the metal. [8][9][10] These planar-chiral compounds have been separated into enantiomers and used as catalysts for asymmetric reactions of aromatic hydroxamates 8 and oximes 11 with alkenes.…”