| Summary: | Enantiopure <i>N</i>-heterocyclic carbene half-sandwich metal complexes of the general formula [Cp*M(C^C:)I] (M = Rh, Ir; C^C: = NI-NHC; NI-H = Naphthalimide; NHC = <i>N</i>-heterocyclic carbene) are reported. The rhodium compound was obtained as a single isomer displaying six membered metallacycle and was resolved on chiral column chromatography to the corresponding enantiomers (<i>S</i>)-[Cp*Rh(C^C:)I] (<i>S</i>)-<b>2</b> and (<i>R</i>)-[Cp*Rh(C^C:)I] (<i>R</i>)-<b>2</b>. The iridium congener, however, furnishes a pair of regioisomers, which were resolved into (<i>S</i>)-[Cp*Ir(C^C:)I] (<i>S</i>)-<b>3</b> and (<i>R</i>)-[Cp*Ir(C^C:)I] (<i>R</i>)-<b>3</b> and (<i>S</i>)-[Cp*Ir(C^C:)I] (<i>S</i>)-<b>4</b> and (<i>R</i>)-[Cp*Ir(C^C:)I] (<i>R</i>)-<b>4</b>. These regioisomers differ from each other, only by the size of the metallacycle; five-membered for <b>3</b> and six-membered for <b>4</b>. The molecular structures of (<i>S</i>)-<b>2</b> and (<i>S</i>)-<b>4</b> are reported. Moreover, the chiroptical properties of these compounds are presented and discussed. These compounds display exceptional stable configurations at the metal center in solution with enantiomerization barrier ΔG<sup>≠</sup> up to 124 kJ/mol. This is because the nature of the naphthalimide-NHC clamp ligand and the iodide ligand contribute to their configuration’s robustness. In contrast to related complexes reported in the literature, which are often labile in solution.
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