Luminescent, Enantiopure, Phenylatopyridine Iridium-Based Coordination Capsules

Chepelin, Oleg; Ujma, Jakub; Wu, Xiaohua; Slawin, Alexandra M. Z.; Pitak, Mateusz B.; Coles, Simon J.; Michel, Julien; Jones, Anita C.; Barran, Perdita E.; Lusby, Paul J.

doi:10.1021/ja309031h

Cited by 195 publications

(113 citation statements)

References 56 publications

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“…This is consistent with conversion 55 of mer to fac isomers of [Ir(ppy) 3 ] requiring heating to > 200 C. 17 The previous reports of non-equal ratio of diastereomers with amino acidates 5,8 and phenol oxazolines 6 may reflect difficulties in isolation by column chromatography rather than an intrinsic diastereoselectivity.…”

supporting

confidence: 81%

“…

Our strategy was to prepare diastereomeric complexes [Ir(C^N) 2 (X^Y*)], separate the diastereomers, then remove the 30 chiral auxiliary by protonation and replace it with another bidentate ligand.

…”

mentioning

confidence: 99%

“…However, unlike [Ru(bipy) 3 ] 2+ the resolution of Ir(III) complexes is still in its infancy and very few reports have been published so far. [2][3][4][5][6] Separation by HPLC of the enantiomers of [Ir(ppy) 3 ] (Hppy = phenylpyridine) was reported in 2007, 3 and of [Ir(ppy-R) 2 (acac)] (R = F, OMe, Ph) in 2008. 4 Single 20 diastereomers have been isolated e.g.…”

mentioning

confidence: 99%

“…4 Single 20 diastereomers have been isolated e.g. [Ir(C^N*)] 3 and [Ir(C^N*) 2 (acac)] with enantiopure cyclometallating ligands, 7 or [Ir(C^N) 2 (X^Y*)] (X^Y* = amino acidate 5,8,9 , phenol oxazoline 6 ) with enantiopure X^Y ligands. However, these complexes have chirality at the ligand as well as the metal; hence, 25 the aim of this work was to prepare, on a synthetically useful scale, homochiral cyclometallated Ir(III) complexes which are only chiral at the metal.…”

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confidence: 99%

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Atropisomerism in a thermally switchable, cyclometallated iridium complex

et al. 2012

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5,8,9 , phenol oxazoline 6 ) with enantiopure X^Y ligands. However, these complexes have chirality at the ligand as well as the metal; hence, 25 the aim of this work was to prepare, on a synthetically useful scale, homochiral cyclometallated Ir(III) complexes which are only chiral at the metal.Our strategy was to prepare diastereomeric complexes [Ir(C^N) 2 (X^Y*)], separate the diastereomers, then remove the 30 chiral auxiliary by protonation and replace it with another bidentate ligand. A similar strategy has recently been applied by Meggers for the synthesis of homochiral trisbidentate ruthenium complexes, 10 and in 2012 was applied to iridium complexes for the first time. 5 35 The dimer [Ir(ppz) 2 Cl] 2 (a, Hppz = phenylpyrazole) was reacted with 2.2 equiv of (S)-Na(L1) 11,12 in a mixture of DCM/ methanol (2:1) at room temperature for 2-4 hrs, to give 1a as a (1:1) mixture of diastereomers, ∆S and ΛS, in good combined 45 yields (>75%) (Scheme 1). The reaction was repeated with only 0.8 equiv of (S)-Na(L1) per dimer and the 1 H NMR spectrum of the product showed a 1:1 ratio of the two diastereomers along with the unreacted excess dimer. This suggests that there is no diastereoselectivity in the synthesis and there is an equal 50 probability for the formation of the two diastereomers. The diastereomers of 1a could be separated by crystallisation from different solvents and they do not interconvert in solution, suggesting the chirality at the metal is stable at room temperature. The absolute configuration of both diastereomers was determined 55 by X-ray crystallography 13 and the structures of S-and S-1a are shown in Fig. 2. 14 The structures show that both isomers have cis carbon atoms and trans nitrogen atoms for the C^N ligands and S configuration at the chiral carbon atom of the oxazoline ligand; one isomer has a Λ configuration at the Ir centre (Fig. 2 60 left), whereas the other isomer shows a ∆ configuration (Fig. 2 right). The change in chirality at the metal leads to different orientations of L1 with respect to the [Ir(C^N) 2 ] fragment. In the ΛS isomer the pyrazole [N(4)-C(12)] pointing towards the oxazoline nitrogen is on the unsubstituted side of the oxazoline 65 and there is no steric conflict. In contrast, in the ∆S isomer, the pyrazole [N(2)-C(3)] pointing towards the oxazoline nitrogen is on the same side as the isopropyl which leads to steric congestion which is clearly evident in the planarity of L1 (Fig. 2 right). Thus, in the ΛS isomer the angle between the planes of the 70 phenol and the oxazoline is less than 3 whilst in the ∆S isomer the corresponding angle is > 20.The structures are retained in solution as determined by key NOEs between the X^Y ligand and the [Ir(C^N) 2 ] fragment (see ESI Fig S1). In ΛS-1a the isopropyl group lies above a ppz ligand

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supporting

confidence: 81%

“…

Our strategy was to prepare diastereomeric complexes [Ir(C^N) 2 (X^Y*)], separate the diastereomers, then remove the 30 chiral auxiliary by protonation and replace it with another bidentate ligand.

…”

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Atropisomerism in a thermally switchable, cyclometallated iridium complex

et al. 2012

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“…4 Single diastereomers have been isolated e.g. [Ir(C^N*)] 3 and [Ir(C^N*) 2 (acac)] with enantiopure cyclometallating ligands, 7 or [Ir(C^N) 2 (X^Y*)] (X^Y* = amino acidate, 5,8,9 phenol oxazoline 6 ) with enantiopure X^Y ligands. However, these complexes have chirality at the ligand as well as the metal; hence, the aim of this work was to prepare, on a synthetically useful scale, homochiral cyclometallated Ir(III) complexes which are only chiral at the metal.…”

mentioning

confidence: 99%

Preparation of single enantiomers of chiral at metal bis-cyclometallated iridium complexes

Davies

Singh

et al. 2013

Chem. Commun.

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) with enantiopure X^Y ligands. However, these complexes have chirality at the ligand as well as the metal; hence, the aim of this work was to prepare, on a synthetically useful scale, homochiral cyclometallated Ir(III) complexes which are only chiral at the metal.Our strategy was to prepare diastereomeric complexes [Ir(C^N) 2 (X^Y*)], separate the diastereomers, then remove the chiral auxiliary by protonation and replace it with another bidentate ligand. A similar strategy has recently been applied by Meggers for the synthesis of homochiral trisbidentate ruthenium complexes, 10 and in 2012 was applied to iridium complexes for the first time. 5The dimer [Ir(ppz) 2 Cl] 2 (a, Hppz = phenylpyrazole) was reacted with 2.2 equiv. of (S)-Na(L1) 11,12 in a mixture of DCMmethanol (2 : 1) at room temperature for 2-4 hours, to give 1a as a (1 : 1) mixture of diastereomers, DS and LS, in good combined yields (>75%) (Scheme 1). The reaction was repeated with only 0.8 equiv. of (S)-Na(L1) per dimer and the 1 H NMR spectrum of the product showed a 1 : 1 ratio of the two diastereomers along with the unreacted excess dimer. This suggests that there is no diastereoselectivity in the synthesis and there is an equal probability for the formation of the two diastereomers. The diastereomers of 1a could be separated by crystallisation from different solvents and they do not interconvert in solution, suggesting the chirality at the metal is stable at room temperature. The absolute configuration of both diastereomers was determined by X-ray crystallography 13 and the structures of LS-and DS-1a are shown in Fig. 1. 14 The structures show that both isomers have cis carbon atoms and trans nitrogen atoms for the C^N ligands and S configuration at the chiral carbon atom of the oxazoline ligand; one isomer has a L configuration at the Ir centre (Fig. 1, left), whereas the other isomer shows a D configuration (Fig. 1, right). The change in chirality at the metal leads to different orientations of L1 with respect to the

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Enantiomerenreine wasserlösliche [Fe₄L₆]‐Käfigverbindungen: Wirt‐Gast‐Chemie und katalytische Aktivität

2013

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Luminescent, Enantiopure, Phenylatopyridine Iridium-Based Coordination Capsules

Cited by 195 publications

References 56 publications

Atropisomerism in a thermally switchable, cyclometallated iridium complex

Atropisomerism in a thermally switchable, cyclometallated iridium complex

Preparation of single enantiomers of chiral at metal bis-cyclometallated iridium complexes

Enantiomerenreine wasserlösliche [Fe₄L₆]‐Käfigverbindungen: Wirt‐Gast‐Chemie und katalytische Aktivität

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Luminescent, Enantiopure, Phenylatopyridine Iridium-Based Coordination Capsules

Cited by 195 publications

References 56 publications

Atropisomerism in a thermally switchable, cyclometallated iridium complex

Atropisomerism in a thermally switchable, cyclometallated iridium complex

Preparation of single enantiomers of chiral at metal bis-cyclometallated iridium complexes

Enantiomerenreine wasserlösliche [Fe4L6]‐Käfigverbindungen: Wirt‐Gast‐Chemie und katalytische Aktivität

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Enantiomerenreine wasserlösliche [Fe₄L₆]‐Käfigverbindungen: Wirt‐Gast‐Chemie und katalytische Aktivität