Macrocycles Containing Tin. Solid Complexes of Anions Encrypted in Macrobicyclic Lewis Acidic Hosts

Article abstract of DOI:10.1021/ja00198a047

Crystalline complexes of 1,10-dichloro-1,10-distannabicyclo<8.8.8>hexacosane and benzyltriphenylphosphonium chloride (complex 3) and of 1,8-dichloro-1,8-distannabicyclo<6.6.6>eicosane and tetrabutylammonium fluoride (complex 4) have been studied by X-ray crystallography and solid-state (119)Sn NMR spectroscopy.The halide ions are encrypted within the cavities of the bicyclic hosts in both complexes.Complex 3 is a stannate-stannane species wherein one of the Lewis acidic tins binds the chloride strongly, and the other interacts with the chloride only weakly.Complex 4 is a bis-hemistannate species wherein the Lewis acidic tin atoms bind the guest fluoride simultaneously.Low-temperature solution (119)Sn NMR spectra of the two complexes in halogenated solvents were studied.A chloride jump from one tin to the other was observed in complex 3; the dynamic process has an activation energy of 5.3 kcal/mol.Line broadening of the tin signals in complex 4 was consistent with a similar fluoride jump with an activation energy of 2.9 kcal/mol.The crystalline complexes were reasonable models for the solution complexes in both cases, and the structural features in the solid state can be used to rationalize the binding energies in solution.