PHOTOCHEMICAL-REACTIONS OF TRANSITION-METAL ORGANYL COMPLEXES WITH OLEFINS .4. [4+5]CYCLOADDITION OF CONJUGATED DIENES ON TRICARBONYL-ETA-5-2,4-PENTADIENYLMANGANESE

Tricarbonyl-eta-5-2,4-pentadienyl-manganese (1) reacts photochemically with the conjugated dienes 1,3-butadiene (A), 2-methyl-1,3-butadiene (B), Z-1,3-pentadiene (C), E-1,3-pentadiene (D), E,E-2,4-hexadiene (E), 2,4-hexadien-1-ol (F), and 2,4-hexadienoic acid methyl ester (G) in a formal [4 + 5] cycloaddition to tricarbonyl manganese complexes with correspondingly substituted eta-3:2-2,6-cyclononadiene-1-yl ligands (2A-2G). The reaction of 1 and A also yields tetracarbonyl-eta-3-Z,E,Z-3,6,8-nonatriene-2-yl-manganese (3A) as by-product. No cycloaddition is observed when 1 and cyclohexadiene (H) are irradiated. The reaction yields tetracarbonyl-eta-3-E-5-(4-penten-1,3-diyl)-1,?? 3-cyclohexadiene-manganese (3H), dicarbonyl-eta-4:3-Z,Z-5-(3-penten-1,2-diyl)-1,?? 3-cyclohexadiene-manganese (4H), and dicarbonyl-eta-5:2-Z-6-(3-penten-1-yl)-2,4-cyclohexadien-1-yl-?? manganese (4H'). Under ambient conditions the complexes 4H and 4H' react with CO to give 3H. The complexes 2A-4H' were characterised by IR and H-1 NMR spectroscopy.