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A multi-iron system capable of rapid N2 formation and N2 cleavage.

MacLeod KC, Vinyard DJ, Holland PL - J. Am. Chem. Soc. (2014)

Bottom Line: Surprisingly, these mild reagents generate high yields of iron(I) products from the iron(II/III) starting material.This is the first molecular system that both breaks and forms the triple bond of N2 at room temperature.These results highlight the ability of multi-iron species to decrease the energy barriers associated with the activation of strong bonds.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Yale University , 225 Prospect Street, New Haven, Connecticut 06520, United States.

ABSTRACT
The six-electron oxidation of two nitrides to N2 is a key step of ammonia synthesis and decomposition reactions on surfaces. In molecular complexes, nitride coupling has been observed with terminal nitrides, but not with bridging nitride complexes that more closely resemble catalytically important surface species. Further, nitride coupling has not been reported in systems where the nitrides are derived from N2. Here, we show that a molecular diiron(II) diiron(III) bis(nitride) complex reacts with Lewis bases, leading to the rapid six-electron oxidation of two bridging nitrides to form N2. Surprisingly, these mild reagents generate high yields of iron(I) products from the iron(II/III) starting material. This is the first molecular system that both breaks and forms the triple bond of N2 at room temperature. These results highlight the ability of multi-iron species to decrease the energy barriers associated with the activation of strong bonds.

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Zero-field Mössbauerspectra at 80 K. The black circlesare the data, and the red lines are simulations. (Top) Mössbauerspectrum of a frozen benzene solution of the reaction mixture of 1 with CNXyl (12 equiv). The blue line represents the majorproduct of the reaction (3) with δ = 0.15 mm/sand /ΔEQ/ = 0.79 mm/s accountingfor 94% of the sample. The green line represents an unknown byproduct(6% of the sample) with δ = 0.83 mm/s and /ΔEQ/ = 2.16 mm/s. (Bottom) Mössbauer spectrum ofindependently synthesized LFe(CNXyl)3 (3),with a fit having δ = 0.17 mm/s and /ΔEQ/ = 0.81 mm/s. Analogous spectra for the CO reactionare shown in the Supporting Information.
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fig2: Zero-field Mössbauerspectra at 80 K. The black circlesare the data, and the red lines are simulations. (Top) Mössbauerspectrum of a frozen benzene solution of the reaction mixture of 1 with CNXyl (12 equiv). The blue line represents the majorproduct of the reaction (3) with δ = 0.15 mm/sand /ΔEQ/ = 0.79 mm/s accountingfor 94% of the sample. The green line represents an unknown byproduct(6% of the sample) with δ = 0.83 mm/s and /ΔEQ/ = 2.16 mm/s. (Bottom) Mössbauer spectrum ofindependently synthesized LFe(CNXyl)3 (3),with a fit having δ = 0.17 mm/s and /ΔEQ/ = 0.81 mm/s. Analogous spectra for the CO reactionare shown in the Supporting Information.

Mentions: Treatment of a benzene solution of 1 with 12 equivof CNXyl (2,6-dimethylphenyl isocyanide) caused a rapid color changefrom red-brown to green. Mössbauer analysis of a frozen solution(80 K) of the crude reaction mixture showed conversion to a singleproduct (94%) with δ = 0.15 mm/s and /ΔEQ/ = 0.79 mm/s (Figure 2, top).On the basis of its Mössbauer parameters and 1HNMR spectrum (Figure S-12), the predominant(94%) reaction product was identified as a tris(isocyanide) compound,LFe(CNXyl)3 (3).


A multi-iron system capable of rapid N2 formation and N2 cleavage.

MacLeod KC, Vinyard DJ, Holland PL - J. Am. Chem. Soc. (2014)

Zero-field Mössbauerspectra at 80 K. The black circlesare the data, and the red lines are simulations. (Top) Mössbauerspectrum of a frozen benzene solution of the reaction mixture of 1 with CNXyl (12 equiv). The blue line represents the majorproduct of the reaction (3) with δ = 0.15 mm/sand /ΔEQ/ = 0.79 mm/s accountingfor 94% of the sample. The green line represents an unknown byproduct(6% of the sample) with δ = 0.83 mm/s and /ΔEQ/ = 2.16 mm/s. (Bottom) Mössbauer spectrum ofindependently synthesized LFe(CNXyl)3 (3),with a fit having δ = 0.17 mm/s and /ΔEQ/ = 0.81 mm/s. Analogous spectra for the CO reactionare shown in the Supporting Information.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4353015&req=5

fig2: Zero-field Mössbauerspectra at 80 K. The black circlesare the data, and the red lines are simulations. (Top) Mössbauerspectrum of a frozen benzene solution of the reaction mixture of 1 with CNXyl (12 equiv). The blue line represents the majorproduct of the reaction (3) with δ = 0.15 mm/sand /ΔEQ/ = 0.79 mm/s accountingfor 94% of the sample. The green line represents an unknown byproduct(6% of the sample) with δ = 0.83 mm/s and /ΔEQ/ = 2.16 mm/s. (Bottom) Mössbauer spectrum ofindependently synthesized LFe(CNXyl)3 (3),with a fit having δ = 0.17 mm/s and /ΔEQ/ = 0.81 mm/s. Analogous spectra for the CO reactionare shown in the Supporting Information.
Mentions: Treatment of a benzene solution of 1 with 12 equivof CNXyl (2,6-dimethylphenyl isocyanide) caused a rapid color changefrom red-brown to green. Mössbauer analysis of a frozen solution(80 K) of the crude reaction mixture showed conversion to a singleproduct (94%) with δ = 0.15 mm/s and /ΔEQ/ = 0.79 mm/s (Figure 2, top).On the basis of its Mössbauer parameters and 1HNMR spectrum (Figure S-12), the predominant(94%) reaction product was identified as a tris(isocyanide) compound,LFe(CNXyl)3 (3).

Bottom Line: Surprisingly, these mild reagents generate high yields of iron(I) products from the iron(II/III) starting material.This is the first molecular system that both breaks and forms the triple bond of N2 at room temperature.These results highlight the ability of multi-iron species to decrease the energy barriers associated with the activation of strong bonds.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Yale University , 225 Prospect Street, New Haven, Connecticut 06520, United States.

ABSTRACT
The six-electron oxidation of two nitrides to N2 is a key step of ammonia synthesis and decomposition reactions on surfaces. In molecular complexes, nitride coupling has been observed with terminal nitrides, but not with bridging nitride complexes that more closely resemble catalytically important surface species. Further, nitride coupling has not been reported in systems where the nitrides are derived from N2. Here, we show that a molecular diiron(II) diiron(III) bis(nitride) complex reacts with Lewis bases, leading to the rapid six-electron oxidation of two bridging nitrides to form N2. Surprisingly, these mild reagents generate high yields of iron(I) products from the iron(II/III) starting material. This is the first molecular system that both breaks and forms the triple bond of N2 at room temperature. These results highlight the ability of multi-iron species to decrease the energy barriers associated with the activation of strong bonds.

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