Metal-Carbene-Templated Photochemistry in Solution: A Universal Route towards Cyclobutane Derivatives

Summary of main observation and conclusion A series of dicarbene-bridged metallacycles [Ag-2(1)(2)](PF6)(2), [Ag-2(2)(2)](BF4)(2), [Ag-2(3)(2)](PF6)(2), [Ag-2(7)(2)](BF4)(2), [Ag-2(8)(2)](BF4)(2) and [Ag-2(11)(2)](PF6)(2) were obtained in high yields via the reactions of 1,2,4-triazole-, 1,2,3-triazole- and imidazo[1,5-a]pyridine-based ligands with Ag2O in CH3CN. The C=C double bonds in all of the newly synthesized metallacycles went through [2 + 2] photodimerization under UV irradiation condition (lambda = 365 nm, T = 298 K) yielding the dinuclear rctt-cyclobutane-silver(I) complexes [Ag-2(4)](PF6)(2), [Ag-2(5)](BF4)(2), [Ag-2(6)](PF6)(2), [Ag-2(9)](BF4)(2), [Ag-2(10)](BF4)(2) and [Ag-2(12)](PF6)(2), respectively with quantitative yields. Treatment of the these cyclobutane-bridged silver(I) complexes with NH4Cl resulted in the exclusive formation of cyclobutane derivatives after removal of the silver(I) metal ions.