Abstract UV irradiation of hexacarbonyl-μ-η 6: 6-1, 1′-bi (2, 4, 6-cycloheptatrien-1-yl) dichromium (O)(I) in THF in the presence of 1, 3-butadiene (A), E-1, 3-pentadiene (B) and EE-2, 4-hexadiene (C) causes preferentially a twofold [4+ 6]-cycloaddition and formation of the hexacarbonyl-μ-2–5: 8.9-η-2′–5′: 8′, 9′-η-11, 11′-bi (bicyclo-[4.4. 1] undeca-2, 4, 8-trien-11-yl) dichromium (O) complexes (IVA–IVC). Partial decomplexation after the first [ ...