Method for the Preparation of Nonracemic Bis‐Cyclometalated Iridium(III) Complexes

Abstract

Abstract A practical strategy for the generation of virtually enantiomerically pure bis‐cyclometalated iridium(III) complexes is reported. Accordingly, the reactions of [Ir(μ‐Cl)(ppy) 2 ] 2 (ppy = cyclometalating 2‐phenylpyridine) with ( S )‐4‐ tert ‐butyl‐2‐(2′‐hydroxyphenyl)‐2‐oxazoline [( S )‐ 1a ], [Ir(μ‐Cl)(pq) 2 ] 2 (pq = cyclometalating 2‐phenylquinoline) with ( S )‐2‐(2′‐hydroxyphenyl)‐4‐isopropyl‐2‐oxazoline [( S )‐ 1b ], and [Ir(μ‐Cl)(pbt) 2 ] 2 (pbt = cyclometalating 2‐phenylbenzothiazole) with ( S )‐2‐(2′‐hydroxyphenyl)‐4‐isopropyl‐2‐thiazoline [( S )‐ 1d ] afforded diastereomeric mixtures of salicyloxazolinato or salicylthiazolinato complexes Λ/Δ‐[Ir(ppy) 2 {( S )‐ 1a –H}]PF 6 , Λ/Δ‐[Ir(pq) 2 {( S )‐ 1b –H}]PF 6 , and Λ/Δ‐[Ir(pbt) 2 {( S )‐ 1d –H}]PF 6 , respectively, which could be resolved by silica gel flash chromatography. With the individual diastereomers in hand, an acid‐induced substitution of the chiral auxiliaries by achiral bidentate ligands with retention of configuration afforded several iridium complexes Λ‐ or Δ‐[Ir(C ∧ N) 2 (N ∧ N)]PF 6 (C ∧ N = cyclometalating ppy, pq, or pbt; N ∧ N = 2,2′‐bipyridine, 1,10‐phenanthroline, or 2,2′‐biquinoline) with enantiomeric ratio ( er ) values of 24:1 to 230:1.