Abstract
Reaction of (C 5 H 5 )Fe(CO) 2 Na with trans-1-chloropenta-2,4-diene in tetrahydrofuran at -78°C gives (C 5 H 5 )Fe(CO) 2 (η 1 -2,4-pentadienyl) (1) in good yields. Photolysis of 1 in ether at -20°C yields a mixture of (C 5 H 5 )Fe(CO)(η 3 -pentadienyl) (2) and (C 5 H 5 )Fe(η 5 -pentadienyl) (3). Compound 2 exists as two stereoisomers characterized as endo syn-η 3 and exo syn-η 3 by its 1 H NMR and IR spectra. The endo form undergoes facile isomerism to exo form at ambient temperatures. The conversion of 2 to 3 is effected by photolysis. A half-open-sandwich structure is assigned to 3 as inferred from its 1 H and 13 C NMR spectra. © 1986 American Chemical Society.