38905-70-3Relevant academic research and scientific papers
Evidence for the Radical Pair Mechanism in 'Insertion' Reactions of Transition Metal Hydrides with Conjugated Dienes
Thomas, Marian J.,Shackleton, Thomas A.,Wright, Steven C.,Gillis, Daniel J.,Colpa, Johannes P.,Baird, Michael C.
, p. 312 - 314 (1986)
The compounds cpFe(CO)2H and HMn(CO)5 (cp = cyclopentadienyl) react with 1,3-dienes to give the 2-enylmetal products of 1,4-addition of the metal hydrides to the dienes; CIDNP studies indicate that the process involves a radical pair mechanism.
The radical pair mechanism in hydrometalation and stoichiometric hydrogenation reactions of η5-C5H5Fe(CO)2H with conjugated dienes
Shackleton, Thomas A.,Baird, Michael C.
, p. 2225 - 2232 (2008/10/08)
The hydride η5-C5H5Fe(CO)2H reacts with a variety of 1,3-dienes to form both the products of irreversible 1,4-addition of the hydride to the diene and of stoichiometric hydrogen transfer to the diene, i.e. η5-C5H5Fe(CO)2H + CH2=CRCR′=CH2 → η5-C5H5Fe(CO)2CH 2CR=CR′Me 2η5-C5H5Fe(CO)2H + CH2=CRCR′=CH2 → MeCHRCR′=CH2 + CH2=CRCHR′Me + MeCR=CR′Me + [η5-C5H5Fe(CO)2]2 R, R′ = H, alkyl The hydrometalation reactions are first order in both η5-C5H5Fe(CO)2H and diene and zero order in added carbon monoxide, while use of η5-C5H5Fe(CO)2D shows that the reaction exhibits an inverse primary isotope effect. Monitoring of the early stages of the reactions also reveals the development of striking CIDNP polarizations, and it is suggested that these insertion reactions involve hydrogen atom abstraction from η5-C5H5Fe(CO)2H by diene to give [allyl + η5-C5H5Fe(CO)2] radical pairs. In the spin-selective step, the component radicals can then either couple to give the geminate σ-allyl products of hydrometalation or diffuse from the solvent cage and react with a second molecule of η5-C5H5Fe(CO)2H to give the nongeminate products, the monoolefins, and [η5-C5H5Fe(CO)2]2. It is also shown that trace concentrations of thiophenol stabilize η5-C5H5Fe(CO)2H with respect to decomposition to H2 and [η5-C5H5Fe(CO)2]2.
