95420-90-9Relevant academic research and scientific papers
Photochemistry of η4-cyclopentadiene iron tricarbonyl complexes: Transfer of the 5-endo substituent to the iron center following dissociative loss of carbon monoxide
Zou, Chaofeng,Wrighton, Mark S.,Blaha, Josephine Paw
, p. 1452 - 1458 (2008/10/08)
Near-UV irradiation of the complexes (η4-C5H5R1)Fe(CO)3 (R1 = exo-H, Ia; exo-CH2Ph (exo-Ez), Ib) and (η4-C5Me4R1R 2)Fe(CO)3 (R1 = exo-Me, R2 = endo-Me, IIa; R1 = exo-Me, R2 = endo-H, IIb; R1 = exo-Bz; R2 = endo-Me, IIc) where R1 and R2 are on the doubly allylic carbon, C-5, in an exo and endo position, respectively, results in the dissociative loss of CO. For all complexes the prompt photoproduct is a coordinatively unsaturated, 16e (η4-cyclopentadiene)Fe(CO)2 that can be detected by IR at low temperature, ～77 K. Irradiation (λ > 420 nm) of the 16e species at low temperature (～77 K) results in transfer of the 5-endo substituent to form (η5-cyclopentadienyl)Fe(CO)2R2 (R2 = H, Me) products. Transfer of the 5-endo substituent can also occur thermally upon warmup, but the transfer of the 5-endo group is not very competitive with back-reaction of the 16e species and CO to regenerate the starting (η4-cyclopentadiene)Fe(CO)3 complexes. The 366-nm quantum yield (at 10-7 einstein/min) for CO loss at 298 K in alkane solution is ～0.1; the formation quantum yields for the (η5-cyclopentadienyl)Fe(CO)2H species are also ～0.1, but the formation quantum yields for the (η5-cyclopentadienyl)Fe(CO)2Me species are -2. All results are consistent with thermal or light-activated transfer of the 5-endo substituent (H or Me) following light-induced loss of CO from the parent (η4-cyclopentadiene)Fe(CO)3. The thermal rate of the transfer of a 5-endo-Me vs. a 5-endo-H is much slower on the basis of the thermal rates of reactions of (η4-C5Me5R2)Fe(CO) 2(1-pentene) (R2 = endo-H or endo-Me) which give (η5-C5Me5)Fe(CO)2R2.
