Mesomerization of S 4 ‐Symmetric Tetrahedral Chelate Complex [In 4 (L 3 ) 4 ]: First‐Time Monitored by Temperature‐Dependent 1 H NMR Spectroscopy

VT 1 H NMR spectroscopy proved that a non‐dissociative and reversible mesomerization process links the tetranuclear indium(III) complexes meso ‐(Δ,Δ,Λ,Λ)( P , P , M , M )‐ 3 and meso ‐(Λ,Λ,Δ,Δ)( M , M , P , P )‐ 3′ . During this process four tandem Bailar twists, resulting in the (Δ)/(Λ) isomerization at the indium centers, and the ( P )/( M ) inversion of the four coordinating face‐centered, helical ligands (L 3 ) 3– are involved. In addition, gas‐phase DFT calculations (B3LYP/LANL2DZp) revealed a C 1 ‐symmetric transition state (+21.9 kcal mol –1 ) for the mesomerization mechanism which connects 3 and 3′ .