935699-70-0Relevant articles and documents
Reactions of nitrogen oxides with the five-coordinate Fe III(porphyrin) nitrito intermediate Fe(Por)(ONO) in sublimed solids
Kurtikyan, Tigran S.,Hovhannisyan, Astghik A.,Hakobyan, Manya E.,Patterson, James C.,Iretskii, Alexei,Ford, Peter C.
, p. 3576 - 3585 (2007/12/29)
Detailed experimental studies are described for reactions of several nitrogen oxides with iron porphyrin models for heme/NxOy systems. It is shown by FTIR and optical spectroscopy and by isotope labeling experiments that reaction of small increments of NO2 with sublimed thin layers of the iron(II) complex Fe(Por) (For = meso-tetraphenylporphyrinato dianion, TPP, or meso-tetra-p-tolylporphyrinato dianion, TTP) leads to formation of the 5-coordinate nitrito complexes Fe(Por)(η1-ONO) (1), which are fairly stable but very slowly decompose under vacuum giving mostly the corresponding nitrosyl complexes Fe(Por)(NO). Further reaction of 1 with new NO2 increments leads to formation of the nitrato complex Fe(Por)(η2-O2NO) (2). The interaction of NO with 1 at low temperature involves ligand addition to give the nitrito-nitrosyl complexes Fe(Por)(η1-ONO)(NO) (3); however, these isomerize to the nitro-nitrosyl analogs Fe(Por)(η1-NO2)(NO) (4) upon warming. Experiments with labeled nitrogen oxides argue for an intramolecular isomerization ( flipping ) mechanism rather than one involving dissociation and rebinding of NO2. The Fe(III) centers in the 6-coordinate species 3 and 4 are low spin in contrast to 1, which appears to be high-spin, although DFT computations of the porphinato models Fe(P)(nitrite) suggest that the doublet nitro species and the quartet and sextet nitrito complexes are all relatively close in energy. The nitro-nitrosyl complex 4 is stable under an NO atmosphere but decomposes under intense pumping to give a mixture of the ferrous nitrosyl complex Fe(Por)(NO) and the ferric nitrito complex Fe(Por)(η1-ONO) indicating the competitive dissociation of NO and NO2. Hence, loss of NO from 4 is accompanied with nitro → nitrito isomerization consistent with 1 being the more stable of the 5-coordinate NO2 complexes of iron porphyrins.
Reactions of nitrogen oxides with heme models: Spectral characterization of an elusive five-coordinate FeIII(porphyrin) nitrito intermediate
Kurtikyan, Tigran S.,Ford, Peter C.
, p. 492 - 496 (2007/10/03)
(Chemical Equation Presented) The famous five: The elusive five-coordinate nitrito complexes [FeIII(por)(ONO)] (por = meso- tetraphenylporphyrinato dianion or meso-tetra-p-tolylporphyrinato dianion) have been obtained by interaction of low-pres
O atom transfer from nitric oxide catalyzed by Fe(TPP)
Lin,Farmer
, p. 1143 - 1150 (2007/10/03)
The reaction of NO-Fe(TPP) with low pressures of NO gas proceeds through three distinct transformations, the first of which we suggest is the formation of an N-N-coupled, (NO)2 adduct intermediate. The subsequent formation of NO(NO2)Fe(TPP), which under these conditions readily loses NO, suggests that it is formed by addition of free NO2 to the starting nitrosyl. A mechanism is proposed which implies that the addition of a competitive O atom acceptor would lead to catalytic production of N2O. In agreement with the proposed mechanism, the formation of N2O is decoupled from the formation of the nitrite by using PPh3 as the competitive acceptor. The mechanism of O atom transfer was examined by cross-labeling experiments, which show that both O atoms in the intermediate are equivalent, even under catalytic conditions, The formation of an intermediate was confirmed by IR spectroscopy of the heterogeneous reaction of an NO-Fe(TPP) film with gaseous NO, in which transient, isotope-sensitive v(NO) bands are seen prior to NO(NO2)Fe(TPP) formation. Mixed 14N/15N label experiments demonstrate coupling between the two bound nitrosyls in the transient species.
