Asymmetric Synthesis of Enantiomerically Pure Mono- and Binuclear Bis(cyclometalated) Iridium(III) Complexes.

Inorg Chem

MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, China.

Published: June 2016

AI Article Synopsis

  • Researchers synthesized chiral iridium complexes (Λ and Δ configurations) using a strategy involving auxiliary ligands and starting from a racemic precursor, achieving 99% de values.
  • The process produced both enantiopure mono complexes and binuclear complexes, with various chiral ligands, and confirmed configurations through single-crystal analysis and circular dichroism spectroscopy.
  • The study established a correlation between the configuration at the Ir(III) centers and CD spectra, highlighting the stability of these configurations for potential use in asymmetric synthesis of pure iridium complexes.

Article Abstract

Chiral precursors Λ-[Ir(ppy)2(l-pro)] (Λ-L, where ppy is 2-phenylpyridine; pro is proline), Λ-[Ir(ppy)2(MeCN)2](PF6) (Λ-1), Δ-[Ir(ppy)2(d-pro)] (Δ-D), and Δ-[Ir(ppy)2(MeCN)2](PF6) (Δ-1) were synthesized from rac-[(Ir(ppy)2)2Cl2] and l-pro or d-pro by means of the auxiliary ligand strategy with 99% de values. The enantiopure mono complexes Λ/Δ-[Ir(ppy)2(L)](PF6) (L is 2,2'-bipyridine, Λ/Δ-2; L is 2,2'-dipyrimidine (dpm), Λ/Δ-3; L is 2,2'-bibenzimidazole (H2bbim), Λ/Δ-4) with 99% ee values and binuclear complexes ΛΛ/ΔΔ-[(Ir(ppy)2)2(dpm)](PF6)2 (ΛΛ-5 and ΔΔ-5) and ΛΛ/ΔΔ-[(Ir(ppy)2)2(bbim)] (ΛΛ-6 and ΔΔ-6) with 99% de values were synthesized in one step using the corresponding chiral precursors. The absolute configurations at Ir(III) centers of precursor Δ-1, mononuclear Λ-3, and binuclear ΔΔ-6 were confirmed by single-crystal structural analysis and characterized by circular dichroism (CD) spectroscopy. The correlation between the absolute configuration at Ir(III) center and CD spectra was established. The configurations at Ir(III) centers are stable during the reactions, and the chiral precursors can be used for the asymmetric synthesis of enantiomerically pure mono- and polynuclear Ir(III) complexes. Moreover, meso ΛΔ-[(Ir(ppy)2)2(dpm)](PF6)2 (meso-5) and ΛΔ-[(Ir(ppy)2)2(bbim)] (meso-6) were also synthesized using these precursors.

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http://dx.doi.org/10.1021/acs.inorgchem.6b00527DOI Listing

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