Interconversion of tetrahedral [(M)4∩{Mg4(L1)6}]/[In4(L2)4] and cyclic [In6Cl6(L3)6]. Enantiotopization of diastereotopic protons monitored by means of VT 1H NMR spectroscopy

• Published in: European journal of inorganic chemistry 2022-02, Vol.2022 (4), p.n/a
• Main Authors: Bauer, Walter, Maid, Harald, Saalfrank, Rolf W.
• Format: Article
• Language: English
• Subjects: Dynamics; Enantiomerization; Enantiotopization; Helicity; Inorganic chemistry; Ligands; Magnesium; Mesomerization; NMR spectroscopy; Protons; Spectrum analysis; Supramolecular coordination compounds
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.202100694

In this review we report on the enantiomerization of tetrahedral racemic‐[(NH4)4∩{Mg4(L1)6}] monitored by means of variable temperature (VT) 1H NMR spectroscopy. The enantiotopization of the diastereotopic protons is due to simultaneous Bailar twists at the four octahedrally coordinated magnesium centres, synchronized with atropisomerization of the six edge‐bridging ligands (L1)2‐.The VT 1H NMR spectrum of tetrahedral meso‐[In4(L2)4] is coined through the helicity of the four face‐centred tripodal hexadentate ligands (L2)3‐ and can, alike the 1H NMR of cyclic meso‐[In6Cl6(L3)6], be explained by the enantiotopization of the diastereotopic protons via mesomerization. The unique VT‐dependent 1H NMR spectroscopic behaviour of meso‐[In4(L)4] 1 can be explained by an unprecedented dynamic mesomerization process of the identical twins (2Δ,2Λ)(2P,2 M)‐1⇌(2Λ,2Δ)(2 M,2P)‐1’ resulting in the enantiotopization of the diastereotopic groups. To the best of our knowledge, this is the first report on the interconversion of a tetrahedral complex with [M4(L)4] stoichiometry [(L)3−=face‐centred helical ligand)].