The Fluxional Character of (η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)Fe(CO)<sub>2</sub>(η<sup>1</sup>-C<sub>9</sub>H<sub>7</sub>): Evidence for the [4 + 2] Cycloaddition of a Metal-Substituted Isoindene with Tetracyanoethylene
作者:Mark Stradiotto、Donald W. Hughes、Alex D. Bain、Michael A. Brook、Michael J. McGlinchey
DOI:10.1021/om970686c
日期:1997.12.1
The variable-temperature NMR spectra of eta(5)-cyclopentadienyl)Fe(CO)(2)(eta(1)-indenyl), 1, do not exhibit noticeable line-broadening below 70 degrees C, at which point decarbonylation to yield benzoferrocene, 8, is rapid. Nevertheless, 2D-EXSY data show clearly that 1 is indeed fluxional; it undergoes successive [1,5] shifts with an activation energy of similar to 20 kcal mol(-1). Contrary to an earlier report, the intermediate isoindene, 2, is sufficiently long-lived to yield a crystallographically-characterized [4 + 2] (cyloadduct, 10, with tetracyanoethylene.