PHOTOCHEMICAL-REACTIONS OF TRANSITION-METAL ORGANYL COMPLEXES WITH OLEFINS .3. [4 + 5] CYCLOADDITION OF CONJUGATED DIENES TO TRICARBONYL(ETA-5-2,4-DIMETHYL-2,4-PENTADIENYL)MANGANESE

Tricarbonyl(eta-5-2,4-dimethyl-2,4-pentadienyl)manganese (1) reacts photochemically with the acyclic conjugated dienes 1,3-butadiene (A), 2-methyl-1,3-butadiene (B), (E)-1,3-pentadiene (C), (E,E)-2,4-hexadiene (D), 2,4-dimethyl-1,3-pentadiene (E), 2,4-hexadien-1-ol (F), and methyl 2,4-hexadienoate (G) in a formal [4 + 5] cycloaddition to give tricarbonylmanganese complexes with eta-3:2-2,6-cyclononadien-1-yl ligands (2A - 2G). In addition, the reaction of 1 with A yields thermolabile [eta-3:2:2-1-(3-butene-1,2-diyl)-1,3-dimethyl-2,6-cyclononadiene]dicarbonylmanganese (3A) and E,E and E,Z isomers of [eta-3-1-(2-butene-1,1-diyl)-1,3-dimethyl-2,6-cyclononadiene]tetracarbonyl-manganese (4A, 4A') as byproducts. Similarly, 1 reacts with B to form tetracarbonyl[eta-3-1-(3-methyl-2-butene-1,1-diyl)-1,3,6-trimethyl-2,6-cyclononadiene]manganese (4B) in a side reaction. The crystal and molecular structures of tricarbonyl(eta-3:2-1,3,5,5,7-pentamethyl-2,6-cyclononadien-1-yl)manganese (2E) and of 3A are determined by X-ray structure analyses. In each of the formally octahedral complexes unusual long manganese-carbon bonds are found for one coordinated CC double bond of the hydrocarbon ligands.