PHOTOCHEMICALLY INDUCED REACTIONS OF DECACARBONYLDIMANGANESE(0)

Photolysis at ca. 350 nm of Mn2(CO)10 in the presence of each of I2, CH3I, SnI4, CuCl2 - 2 H2O, HgX2 (X Cl, Br or I), C6H5HgI, η5-C5H5Cr(NO)2Cl, (η5-C5H5)2Cr2 (NO)4 and [Co2(CNCH3)10](BF4)4 , generally under N2 or CO in several organic solvents (mainly cyclohexane and THF), was investigated. The observed photoreactions are best rationalized in terms of initial homolytic cleavage of the MnMn bond. In the presence of a halogen (X)-containing compound, the resultant Mn(CO)5· radical abstracts X to yield Mn(CO)5X. These reactions are characterized by high quantum efficiencies (generally, φ-Mn{greater-than or approximate}0.36). Following the abstraction, the remaining metal-containing species (usually a radical), SnCl3·, CuCl, HgX·, C6H5Hg· or η5-C5H5Cr(NO)2·, undergoes further abstraction of halogen by Mn(CO)5·, coupling with the Mn(CO)5· or ligand substitution. Isolated metal-containing products include SnI2, Cu, Mn(CO)5HgX, Hg, [Mn(CO)5]2Hg and η5-C5H5Cr(CO)2NO. Photolysis of Mn2(CO)10 in the presence of each of the metal-metal bonded compounds, (η5-C5H5)2Cr2 (NO)4 and [Co2(CNCH3)10](BF4) 4, does not give the respective heterodinuclear combinations, (η5-C5H5)(NO)2 CrMn(CO)5 and [(CH3NC)5CoMn(CO)5]2+, as detectable or isolable species; instead, η5-C5H5Cr(CO)2NO, Mn(CO)4NO, Mn2(CO)9CNCH3, and [Mn(CO)(CNCH3)5]+ are among the isolated products. The photoreaction between Mn2(CO)10 and CH3I provides a convenient synthesis of Mn(CO)5I. © 1979.