Non‐Templated Assembly of D5h‐Symmetric Pd5L10 Rings by Precise Ligand Angle Adjustment

Abstract

AbstractWe report a series of Pd(II)nL2n coordination rings for which nuclearity is controlled by the binding angle of the corresponding bis‐monodentate bridging ligands. Judicious choice of the angle within a family of rather rigid ligands allowed for the first‐time to synthesize a homoleptic five‐membered Pd5L10 ring that does not require any template to form. We demonstrate that control over the ring size is maintained both in the solid‐, solution‐, and gas‐phase. Two X‐ray structures of five‐membered rings from ligands with ideal angles (yielding a perfect pentagonal ring) vs. suboptimal angles (resulting in a highly distorted structure) illustrate the importance of the correct ligand geometry. A mathematical model for estimating the expected ring size based on the ligand angle was derived and DFT computations show that ring‐strain is the major factor determining the assembly outcome.