Scheme 17.

Synthesis of molecular pentafoil knots (5₁) via circular double helicates. a) Fe₅ 44 is obtained by formation of an imine bond between ligand 42 and diamine 43 in the presence of Fe^II. The size (pentamer) of the circular helicate is determined by a chloride anion template.105 b) The yield of the pentafoil knot is increased by using ligand 45, which allows for covalent capture of the closed‐loop knot by RCM. In contrast to Fe₅ 44, Fe₅ 46 does not decompose upon demetalation.107 c) Solid‐state structure of Fe₅ 46 (the structure of Fe₅ 44 was also determined by X‐ray crystallography).