On-complex three-component cascade reactions involving phosphorescent cyclometalated Ir(iii) chloro-isocyanide complexes, nitriles, and propylamine

TL;DR

A new three-component reaction creates phosphorescent iridium complexes with a unique ligand, expanding organometallic chemistry options.

Contribution

A novel ligand-based functionalization approach to synthesize bis-cyclometalated iridium complexes with an imino-ADC ligand.

Findings

The cascade reaction produces phosphorescent bis-cyclometalated iridium compounds with a new imino-ADC ligand.

The reaction works with various nitriles and isocyanides, and products can be deprotonated to form neutral compounds.

The complexes show blue phosphorescence, with spectral profiles influenced by the cyclometalating ligand.

Abstract

An “on-complex” three-component cascade reaction involving cyclometalated iridium chloro-isocyanide complexes, nitriles, and propylamine is reported. This ligand-based functionalization approach gives access to phosphorescent bis-cyclometalated iridium compounds containing a new chelating imino-acyclic diamino carbene (imino-ADC) ligand, not accessible by traditional organometallic synthesis. The reaction is compatible with alkyl nitriles and iridium complexes bearing different cyclometalating ligands and aromatic isocyanides. The imino-ADC ligand in the resulting cationic products can be deprotonated in a separate step to give the corresponding neutral compounds. The products of the cascade reactions were obtained in low to moderate yields, depending on the isocyanide and nitrile substituents used, with their structures characterized by multinuclear NMR and single-crystal X-ray diffraction. Photophysical measurements show that the complexes described here exhibit blue phosphorescence, with the spectral profile dependent on the cyclometalating ligand, which is either 2,4-difluorophenylpyridine (F2ppy) or 1-phenyl-1H-pyrazole (ppz). The three-component reaction developed here expands the limited library of organometallic multicomponent reactions and gives access to a new structure type for phosphorescent bis-cyclometalated iridium complexes.

Three-component cascade reactions involving bis-cyclometalated iridium isocyanide precursors, propylamine, and an alkyl nitrile furnish imino-acyclic diamino carbene products, further modifiable by deprotonation.

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