A homage to Alfred Werner: Exploring the stereochemical complexity of cyclometallated [Ir(ppy)2XY]n+ complexes (Hppy = 2-phenylpyridine)

The iridium(III) complexes [Ir(ppy)2(2,4′-bpy)Cl], [Ir(ppy)2(2,4′-bpy)2][PF6] and [{Ir(ppy)2Cl}2(μ-4,4′-bpy)] (Hppy = 2-phenylpyridine, 2,4′-bpy = 2,4′-bipyridine, 4,4′-bpy = 4,4′-bipyridine) are reported. Solution NMR spectroscopic data for [Ir(ppy)2(2,4′-bpy)Cl] confirm hindered rotation of the N-coordinated pyridine ring with free rotation about the Cpy–Cpy bond at 298 K on the NMR timescale. On crystallization, racemic [Ir(ppy)2(2,4′-bpy)Cl] spontaneously resolves and the single crystal structure of the Δ-enantiomer is described. Racemic [Ir(ppy)2(2,4′-bpy)2][PF6] crystallizes in the centrosymmetric space group C2/c with two independent cations, one with Δ-handedness and the other Λ; the second enantiomer of each pair is present in the unit cell. Dimethyl sulfoxide displaces 2,4′-bpy from [Ir(ppy)2(2,4′-bpy)Cl] and 4,4′-bpy from [{Ir(ppy)2Cl}2(μ-4,4′-bpy)] and these systems have been investigated using 1H NMR spectroscopy.

Graphical abstractThe complexes [Ir(ppy)2(2,4′-bpy)Cl], [Ir(ppy)2(2,4′-bpy)2][PF6] and [{Ir(ppy)2Cl}2(μ-4,4′-bpy)] (Hppy = 2-phenylpyridine, 2,4′-bpy = 2,4′-bipyridine, 4,4′-bpy = 4,4′-bipyridine) are reported. NMR spectroscopy is used to probe solution behaviour and DMSO-for-bpy exchange, and the crystal structures of Δ-[Ir(ppy)2(2,4′-bpy)Cl] and racemic [Ir(ppy)2(2,4′-bpy)2][PF6] are described.Figure optionsDownload full-size imageDownload as PowerPoint slide