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

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.

Bimetallic Ru(II)–Ir(III) complexes with bridging 2,2′‐bipyrimidine: Synthesis, structures and characterization

“…Ir1 is coordinated by two phenylpyridine ligands with cis ‐metalated C atoms and trans ‐metalated N atoms. The Ir–N and Ir–C lengths are in accordance with the reported L 2 Ir(C^N) 2 complexes . The bond lengths Ir1–N5 (2.136[12] Å) and Ir1–N6 (2.185[13] Å) are slightly longer than those of Ir1–N2 (2.078[13] Å) and Ir1–N3 (2.056[13] Å), indicating that the carbon atoms on the phenylpyridine have strong trans effect .…”

Sky-blue emitting bridged diiridium complexes: beneficial effects of intramolecular π–π stacking

“…This is complementary to using enantiomerically pure dichloro-bridged dimers, as reported for other systems. 49,52 Analogous to the mesityl-functionalised complex 11, the diastereomers rac 13 (stereochemistry confirmed by X-ray diffraction, Fig. 4) and meso 13 were easily separated.…”

Photoaccelerated energy transfer catalysis of the Suzuki–Miyaura coupling through ligand regulation on Ir(iii)–Pd(ii) bimetallic complexes

“…, and [Ir(pq) 2 (bpy)](PF 6 ) were synthesized according to the literatures. [18][19][20][21] Column chromatography was performed with silica gel (300-400 mesh) under low light. Elemental (C, H, and N) analyses were carried out on an Elementar Vario EL analyzer.…”