Sequence of metal-organic oligomer-polymer exchange equilibria in solution:: Supramolecular isomerism, self-assembly dynamics and carboxylate shift of di-n-butyltin cis-1,4-cyclohexanedicarboxylate

Di-n-butyltin dichloride (nBu(2)SnCl(2)) was treated with the potassium salt of cis- 1,4-cyclohexanedicarboxylate (cis-1,4-chdcaK(2)) to give di-n-butyltin cis-1,4-cyclohexanedicarboxylate. In the solid state two supramolecular isomers coexist within the same crystal lattice, the 36-membered macrocyclic tetranuclear complex [{nBu(2)Sn(cis-1,4-chdca)}(4)] and the analogous polymeric form [(nBu(2)Sn(cis-1,4-chdca)}(4)]. In solution, fast (on the NMR time scale) dynamic equilibria were detected. The supramolecular arrangement in the solid state consists of alternating macrocycle and polymer ribbons with different patterns of intermolecular Sn...O interactions that give rise to a total of four different types of supramolecular macrocyclic assemblies. They probably resemble local environments in the liquid phase and allow to propose a plausible mechanistic pathway for the ring-chain rearrangement dynamics during which the macrocycle molecules are transformed into other macrocyclic and polymeric molecules. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).