We have found that irradiation of Cr(CO)6-1-butene mixtures in the gas phase with a KrF laser (248 nm) results in the efficient (yield ∼0.2) isomerization of 1-butene to 2-butene, in marked contrast to results in solution. The primary photochemical yield is independent of 1-butene pressure and of Cr(CO)6 pressure over wide pressure ranges. Secondary photochemical processes are also found, the importance of which depends upon 1-butene pressure. We also report yields of species Cr(CO)m(PF3)6-m resulting from irradiation of Cr(CO)6-PF3 mixtures at 248 nm. At high dilution [Cr(CO)6:PF3 = 2 × 10-3], we find relative yields of 0.10, 0.14, 0.73, and 0.03 for Cr(CO)2(PF3)4, Cr(CO)3(PF3)3, Cr(CO)4(PF3)2, and Cr(CO)5PF3, respectively. These results suggest a high degree of fragmentation following optical excitation at 248 nm. We present a reasonable kinetic model to explain the observed isomerization of butene in which a primary photofragment, probably Cr(CO)3 or Cr(CO)2, is the active species.
|Number of pages||5|
|Journal||Journal of the American Chemical Society|
|Publication status||Published - 1982|
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