Supramolecular Control of Photocycloadditions in Solution: In Situ Stereoselective Synthesis and Release of Cyclobutanes.

A new class of supramolecular metallacycles capable of undergoing photochemical reactions and in situ release of cyclobutanes in solution is described. The molecular metallacycles were generated through coordination-driven self-assembly of dinuclear metal-carbene complexes as organometallic clips with olefin-functionalized bridging ligands. Photolysis of these molecular metallacycles in situ led to structural interconversion and release of the formed cyclobutane products with quantitative conversion. Further modifications of the obtained cyclobutanes provided a series of new species containing the cyclobutane skeleton.