Formation of Iridium(III) Complexes via Selective Activation of the C-H and N-H Bonds of a Dipyridylpyrrole Ligand

Meng Xue; Dan-Ling Zhuang; Hao Li; Piao He; Chao Liu; Jun Zhu; Xiao-Yi Yi

doi:10.1021/acs.inorgchem.9b02560

Formation of Iridium(III) Complexes via Selective Activation of the C-H and N-H Bonds of a Dipyridylpyrrole Ligand

Inorg Chem. 2020 Jan 21;59(2):960-963. doi: 10.1021/acs.inorgchem.9b02560. Epub 2020 Jan 8.

Authors

Meng Xue¹, Dan-Ling Zhuang², Hao Li¹, Piao He¹, Chao Liu¹, Jun Zhu², Xiao-Yi Yi¹

Affiliations

¹ College of Chemistry and Chemical Engineering , Central South University , Changsha , Hunan 410083 , P. R. China.
² State Key Laboratory of Physical Chemistry of Solid Surfaces and Collaborative Innovation Center of Chemistry for Energy Materials, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, and Department of Chemistry, College of Chemistry and Chemical Engineering , Xiamen University , Xiamen , Fujian 361005 , P. R. China.

PMID: 31913025
DOI: 10.1021/acs.inorgchem.9b02560

Abstract

Treatment of [Ir(PPh₃)₃Cl] with 2-[5-(pyridin-2-yl)-1H-pyrrol-2-yl]pyridine (Hdpp) in refluxing toluene affords an unexpected pyrrole-metalated iridium(III) hydride complex, [Ir(K²_C,N-dpp)(H)(Cl)(PPh₃)₂] (1), via C_pyrrole-H activation, while the presence of the base KO^tBu as the deprotonation reagent produces a pyridine-metalated iridium(III) hydride complex, [Ir(K³_C,N,N-dpp)(H)(PPh₃)₂] (2), via C_pyridine-H activation. Treatment of [Ir(PPh₃)₃Cl] prepared by a convenient method with Hdpp in the presence of KO^tBu under the refluxing mixture solvent toluene/methanol (2:1, v/v) generates the N,N-chelating complex [Ir(K²_N,N-dpp)(H)(Cl)(PPh₃)₂] (3) together with 1 and the N,N-chelating dihydride complex [Ir(K²_N,N-dpp)(H)₂(PPh₃)₂] (4). Complex 4 is also readily produced by the reaction of [Ir(PPh₃)₃Cl] and Hdpp in the presence of KO^tBu under refluxing methanol or by the reaction of IrCl₃ and PPh₃ in refluxing 2-ethoxyethanol. Complexes 1-4 are fully characterized by NMR, IR, and UV-vis spectroscopy and X-ray diffraction analysis. The dpp^-/dpp^2- ligand shows rich coordination capability, of which pyridine- and pyrrole-cyclometalated coordination modes are first reported. The formation of structural isomers 1 and 3 involved the selective activation of the C-H and N-H bonds of Hdpp is rationalized by theoretical calculations.