Photolysis of (Eta-5-C5h5)Fe(Co)2(Butadienyl) Complexes - Synthesis and Electrocyclic Ring-Closure of (Eta-5-C5h5)Fe(Pentadienoyl) Complexes to Hydroxyferrocenes

by Dawson, David P.; Yongskulrote, Warunee; Bramlett, J. Morris; Wright, J. B.; Durham, B.; Allison, Neil T.

A study of the synthesis and photolysis of seven (eta5-C5H5)Fe(CO)2(eta1-1,3-butadienyl) complexes is reported. Photolysis of these complexes leads to the formation of the rarely accessible class of substituted hydroxyferrocenes in very high yields. Low-temperature experiments aimed at elucidating the mechanism of this conversion indicate that loss of a terminal carbonyl from (eta5-C5H5)Fe(CO)2(eta1-1,3-butadienyl) complexes is the only photochemical reaction and that (eta5-C5H5)Fe(eta5-pentadienoyl) complexes are intermediates. Spectroscopic data for two kinetically unstable pentadienoyl intermediates are presented. Pentadienoyl ligands undergo electrocyclic ring closure followed by keto-enol tautomerization to give the hydroxycyclopentadienyl ligands. Acid catalyzes this ring-closure reaction with the rate of closure being linearly dependent on the concentration of acid. Ring strain and electronic effects also influence the rate of formation of substituted bicyclic hydroxyferrocenes.

Journal
Organometallics
Volume
13
Issue
10
Year
1994
Start Page
3873-3880
URL
https://dx.doi.org/10.1021/om00022a024
ISBN/ISSN
1520-6041; 0276-7333
DOI
10.1021/om00022a024