Tricarbonylbis(.eta.2-cis-cyclooctene)iron: photochemical synthesis of a versatile tricarbonyliron source for olefin isomerization and preparative applications

Fleckner, Helmut; Grevels, Friedrich‐Wilhelm; Hess, Dieter

doi:10.1021/ja00319a021

Cited by 99 publications

(60 citation statements)

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“…8,9,11,13,14,16,17,34 Table 2 and Figure 3). However, our calculations also show evidence for a self-solvated form of Fe(CO) 3 11 given the accuracy of DFT calculations. 43 As a result, we cannot distinguish between the structures using their calculated CO stretching frequencies alone.…”

Section: A Mechanism For the Formation Of Hfe(co) 3 (η 3 -C 4 H 7 ) (C)supporting

confidence: 57%

“…13,14 In the gas phase, UVirradiation of Fe(CO) 5 leads to the dissociation of two CO ligands to form 3 Fe(CO) 3 . 9,11,[18][19][20] It is hypothesized that 3 Fe(CO) 3 coordinates a single 1-pentene molecule via a spin-allowed process to form Recently, Glascoe et al performed a similar experiment on a picosecond time-scale and found that after 266-nm excitation of A a single CO is dissociated to form B 1 within a few ps. 11 Species B 1 does not react on the time-scale of the ultrafast experiments (τ < 5 ns) and neither C nor D was observed, presumably because the B 1 C and B 1 D reactions occur on a longer time-scale.…”

Section: 14mentioning

confidence: 99%

“…1 Photoactivated Fe(CO) 5 , which is used to catalyze alkene isomerization, is a particularly efficient catalyst, and as a result, it has been used by synthetic chemists for decades. [1][2][3][4][5][6][7] Numerous mechanistic studies have resolved the key intermediates in the isomerization reaction under a variety of conditions (gas-and solution-phase and low temperature matrices), 3,4,6-17 yet many questions remain about the mechanism in room-temperature solution, particularly concerning the role of high spin…”

Section: Introductionmentioning

confidence: 99%

“…Since species B 1 has been proposed to be most stable in the triplet spin state, we have modeled the formation of C from the triplet potential of Fe(CO) 3 (η 2 -1-butene) (B 1 ). One-dimensional slices of ground singlet (S 0 ) and triplet (T 1 ) potential energy surfaces were calculated by performing successive partial geometry optimizations and energy calculations in the triplet and singlet spin states of B 1 at fixed distances between the iron and the γ-hydrogen (ca.…”

mentioning

confidence: 99%

“…Kinetics plots for the C and D peaks are displayed in Figure 2 and are both well fit to a biexponential function (solid red line). Figure 2 The small peak centered at 1930 cm -1 is assigned to an alkyl-solvated form of Fe(CO) 3 (η 2 -1-hexene)(alkyl) (E), solvated either by the alkyl portion of the 1-hexene ligand or the alkyl portion of a token ligand from the bath. We have performed control experiments of A in solution with neat cyclohexane and found a similar species.…”

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confidence: 99%

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Mechanism for Iron-Catalyzed Alkene Isomerization in Solution

et al. 2008

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ABSTRACT.Here we report nano-through microsecond time-resolved IR experiments of iron-catalyzed alkene isomerization in room-temperature solution. We have monitored the photochemistry of a model system, Fe(CO) 4 (η 2 -1-hexene), in neat 1-hexene solution. UV-photolysis of the starting material leads to the dissociation of a single CO to form Fe(CO) 3 (η 2 -1-hexene), in a singlet spin state. This CO loss complex shows a dramatic selectivity to form an allyl hydride, HFe(CO) 3 (η 3 -C 6 H 11 ), via an internal C-H bondcleavage reaction in 5-25 ns. We find no evidence for the coordination of an alkene molecule from the bath to the CO loss complex, but do observe coordination to the allyl hydride, indicating that it is the key intermediate in the isomerization mechanism. Coordination of the alkene ligand to the allyl hydride leads to the formation of the bis-alkene isomers, Fe(CO) 3 (η 2 -1-hexene)(η 2 -2-hexene) and Fe(CO) 3 (η 2 -1-hexene) 2 . Because of the thermodynamic stability of Fe(CO) 3 (η 2 -1-hexene)(η 2 -2-hexene) over Fe(CO) 3 (η 2 -1-hexene) 2 (ca. 12 kcal/mol), nearly 100% of the alkene population will be 2-alkene. The results presented herein provide the first direct evidence for this mechanism in solution and suggest modifications to the currently accepted mechanism.

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