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 [Fe(3)(CO)(12)] or [Fe(CO)(4)PPh(3)] in hexane was investigated. The Fourier transform infrared (FTIR) absorption spectra of iron-carbonyl intermediate species such as [Fe(CO)(5)], [Fe(CO)(4)(R-C(3)H(4)OH)], and more importantly the pi-allyl iron-carbonyl hydride species [FeH(CO)(3)(R-C(3)H(3)OH)] (R=H, Me, Ph) were recorded during the catalytic process using [Fe(3)(CO)(12)] as the catalytic precursor. When [Fe(CO)(4)PPh(3)] was photolyzed with 355 nm, [FeH(CO)(3)(R-C(3)H(3)OH)] was also generated indicating the common occurrence of the species in these two systems. The pi-allyl hydride species is long believed to be a key intermediates and its detection here lends support to the pi-allyl mechanism of the photoisomerization of allyl alcohols.

Combined 1 H NMR and DFT study of the solvent effects on the iron pentacarbonyl-catalyzed photo-assisted isomerization of allyl alcohol

“…The isomerization has been shown to occur through heating of the allylic alcohol and IPC, as well as through UV irradiation . Transient Fourier transform infrared (FTIR) experiments have shown that the photo‐induced isomerization of allyl alcohol to propanal in hexane occurs after IPC has successively lost two carbonyl ligands to form the important tricarbonyl intermediate, Fe(CO) 3 ●(η 2 ‐alkene) . In this paper, we report the results of a 1 H NMR and computational study of the rate of the IPC‐catalyzed photo‐induced isomerization of allyl alcohol in solvents of different coordination strengths.…”

“…Iron pentacarbonyl (IPC) has been widely used in conjunction with ultraviolet (UV) light to catalyze a number of alkene isomerization reactions . The exact mechanisms for these reactions have been studied through computational, static, and ultrafast experimental techniques . These studies all suggest that formation of the key intermediate Fe(CO) 3 ●(η 2 ‐alkene) is necessary to induce the hydride shift leading to isomerization.…”

“…The photo‐assisted isomerization of allyl alcohol to propanal is a prototypical example of a reaction facilitated by the iron tricarbonyl intermediate . This reaction is representative of a broader class of reactions in which organometallic compounds catalyze the isomerization of allylic alcohols to saturated carbonyl compounds, circumventing the need for separate oxidation and reduction steps .…”

Direct Synthesis of Single Crystalline $\alpha$-Fe Nanoparticles With High Saturation Magnetization by Mixed Surfactant

“…Fig. 3 shows residual amount of Fe(CO) at a certain reaction time estimated from the ratio of IR absorption area to that at 1 s at 2000 and 2020 cm , which corresponds to CO stretch vibration [12], [13]. Fig.…”

Synthesis of Monodisperse Iron Nanoparticles with a High Saturation Magnetization Using an Fe(CO)x−Oleylamine Reacted Precursor

“…In this paper, we report a newly developed synthesis of Fe NPs by thermal decomposition of a precursor with less CO, which was obtained through reaction of Fe(CO) 5 and oleylamine (OAm). It is well-known that the iron carbonyl as typified by Fe(CO) 5 forms an intermediate in combination with various ligands . Fe(CO) 5 and OAm formed an alternative precursor of Fe(CO) x −OAm ( x < 5), where it is expected that some of the CO ligands are displaced by OAm.…”