MECHANISMS OF PYROLYSIS OF TRICARBONYLCYCLOPENTADIENYLMANGANESE AND TRICARBONYL(METHYLCYCLOPENTADIENYL)MANGANESE

The mechanisms of the gas-phase pyrolysis of tricarbonylcyclopentadien ylmanganese (1) and tricarbonyl(methylcydopentadienyl)manganese (2) ha ve been investigated using a combination of IR laser-powered homogeneo us pyrolysis, stirred flow reactor kinetic measurements, and matrix is olation ESR spectroscopy. The observations are consistent with initial stepwise loss of CO, followed ultimately by release of . C5H5 (for 1) or . C5H4CH3 (for 2); the hydrocarbon radicals then abstract hydrogen from unreacted starting material. For 1, the resultant . C5H4Mn unit undergoes intramolecular rearrangement, yielding ethyne and a second s pecies tentatively identified as a manganese carbide. For 2, the more rapid abstraction from the ring CH3 group results in formation of the fulvene CH2C5H4 followed by isomerization to benzene. These processes lead to heavy carbon contamination of deposited Mn films unless an alt ernative source of H atoms for abstraction by cyclopentadienyl radical s is present.