Synthesis, Structure, and Dynamics of Six-Membered Metallacoronands and Metallodendrimers of Iron and Indium

In the reaction of the N‐substituted diethanolamines (H2L1–3) (1–3) with calcium hydride followed by addition of iron(III) or indium(III) chloride, the iron wheels [Fe6Cl6(L1)6] (4) and [Fe6Cl6(L2)6] (6) or indium wheels [In6Cl6(L1)6] (5), [In6Cl6(L2)6] (8) and [In6Cl6(L3)6] (9) were formed in excellent yields. Exchange of the chloride ions of 6 by thiocyanate ions afforded [Fe6(SCN)6(L2)6] (7). Whereas the structures of 4, 5 and 7 were determined unequivocally by single‐crystal X‐ray analyses, complexes 8 and 9 were characterised by NMR spectroscopy. Contrary to what is normally presumed, the scaffolds of six‐membered metallic wheels are not generally rigid, but rather undergo nondissociative topomerisation processes. This was shown by variable temperature (VT) 1H NMR spectroscopy for the indium wheel [In6Cl6(L1)6] (5) and is highlighted for the enantiotopomerisation of one indium centre {${{ 1/6 }}$[S6‐5] ⇄ ${{ 1/6 }}$[S6‐5′]}. The self‐assembly of metallic wheels, starting from diethanolamine dendrons, is an efficient strategy for the convergent synthesis of metallodendrimers. Contrary to what is generally presumed, the scaffolds of six‐membered metallic wheels are not generally rigid, but rather undergo nondissociative topoisomerisation processes. This was shown by VT 1H NMR spectroscopy for the indium wheel [In6Cl6(L1)6] and is highlighted here for the enantiotopomerisation of one indium centre {${{{ 1/6 }}}$[S6‐1] ⇄ ${{{ 1/6 }}}$[S6‐1′]}.