FTIR studies of iron-carbonyl intermediates in allylic alcohol photoisomerization

Abstract

The 532 or 355 nm laser-induced photoisomerization of allylic alcohols to aldehydes catalyzed by [Fe3(CO)12] or [Fe(CO) 4PPh3] in hexane was investigated. The Fourier transform infrared (FTIR) absorption spectra of iron-carbonyl intermediate species such as [Fe(CO)5], [Fe(CO)4(RC3H4OH)], and more importantly the π-allyl iron-carbonyl hydride species [FeH(CO) 3(R-C3H3OH)] (R = H, Me, Ph) were recorded during the catalytic process using [Fe3(CO)12] as the catalytic precursor. When [Fe(CO)4PPh3] was photolyzed with 355 nm, [FeH(CO)3(R-C3H3OH)] was also generated indicating the common occurrence of the species in these two systems. The π-allyl hydride species is long believed to be a key intermediates and its detection here lends support to the π-allyl mechanism of the photoisomerization of allyl alcohols. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.