79121-26-9Relevant articles and documents
Kinetics and Mechanism of Oxygen Transfer in the Reaction of p-Cyano-N,N-dimethylaniline N-Oxide with Metalloporphyrin Salts. 7. Oxygen Atom Transfer to and from (meso-Tetrakis(pentafluorophenyl)porphinato)iron(III) Chloride
Ostovic, Drazen,Knobler, Carolyn B.,Bruice, Thomas C.
, p. 3444 - 3451 (2007/10/02)
The decomposition of p-cyano-N,N-dimethylaniline N-oxide (NO) in the presence of (meso-tetrakis(pentafluorophenyl)porphinato)iron(III) chloride ((F20TPP)FeIIICl) provides p-cyano-N,N-dimethylaniline (DA) in 32 +/- 3percent, p-cyano-N-methylaniline (MA) in 50 +/- 5percent, 4-cyano-7-(dimethylamino)-2-benzofuranone-3-spiro-2'-cyano-5'-(dimethylamino)cyclopentadiene (BF) in 16 +/- 2percent, and formaldehyde in 30 +/- 3percent yield based upon (NO)i.Material balance may be accounted for in all components.Appearance of products is first order in both NO and (F20TPP)FeIIICl, and the second-order rate constant for the reaction has been determined to be (2.0 +/- 0.5) x 102 M-1 s-1.The observation that the formation of products DA, MA, and BF is associated with the same rate constant establishes the commitment step to be the bimolecular reaction of NO with (F20TPP)FeIIICl.It is proposed that this reaction directly yields DA and the iron(IV)-oxo porphyrin ?-cation radical ((+.F20TPP)FeIVO).That the formation of (+.F20TPP)FeIVO + DA is rate controlling is substantiated by use of the reagents 2,4,6-tri-tert-butylphenol (TBPH), N,N-dimethylaniline (DMA), and N,N-dimethyltoluidine (DMT) as traps for the (+.F20TPP)FeIVO species.The rates of oxidation of these trapping agents are independent of their concentration, and the rate constants calculated for the appearances of their oxidation products correspond to the turnover rate constant for the reaction of NO with (F20TPP)FeIIICl in the absence of trapping agents.Formation of the products MA and BF must then be attributed to the rapid oxidation of DA by (+.F20TPP)FeIVO.The formation of MA occurs by the oxidative demethylation of DA, and formation of BF is logically accounted for by the hydroxylation of DA to yield 2-hydroxy-4-cyano-N,N-dimethylaniline (DMP) which, on further stepwise oxidation, provides BF (much as in the stepwise 1 e- oxidation of p-cresol to yield Pumerer's ketone).Increase in the concentrations of DMA and DMT results in exponential increase in the percentage yield of DA and decrease in the percentage yield of MA.In each case the asymptotic percentage yields of 68 +/- 7percent DA and 17 +/- 2percent MA are approached.The percentage yield of BF (17 +/- 2percent) is not changed by the presence of DMA or DMT at various concentrations or by their absence.These results show that a substantial portion of the immediate products DA and (+.F20TPP)FeIVO reacts in a solvent-caged /(+.F20TPP)FeIVO*DA/ pair prior to their diffusion apart.Once free from the caged pair, the (+.F20TPP)FeIVO species oxidizes the traps DMA and DMT in preference to DA.The asymptotic yield of MA represents the percentage yield of MA obtained by oxidation of DA within the solvent caged pair.Since the percentage yield of BF is not influenced by the presence of DMA or DMT, all hydroxylation of DA must occur within the /(+.F20TPP)FeIVO*DA/ species.By this reasoning, both the caged oxidative demethylation and hydroxylation of DA occur in ca. 17percent yields.Thus, within the ....
Kinetics and Mechanism of Oxygen Transfer in the Reaction of p-Cyano-N,N-dimethylaniline N-Oxide With Metalloporphyrin Salts. 6. Oxygen Atom Transfer to and from the Iron(III) C2cap Porphyrin of Baldwin
Bruice, Thomas C.,Dicken, C. Michael,Balasubramanian, P. N.,Woon, T. C.,Lu, Fu-Lung
, p. 3436 - 3443 (2007/10/02)
The decomposition of p-cyano-N,N-dimethylaniline N-oxide (NO) is catalyzed (CH2Cl2 solvent at 25 deg C) by the SbF6- salt of the C2-capped (meso-tetraphenylporphinato)iron(III) of Baldwin ((TPPC2cap)FeIIISbF6).Since neither NO nor the SbF6- anion can fit under the cap, this result establishes that oxygen transfer from NO to the iron(III) center can occur without the intermediate iron(IV)-oxo porphyrin ?-cation being hexacoordinated.The products of NO decomposition (p-cyano-N,N-dimethylaniline (DA) 68percent, p-cyano-N-methylaniline (MA) 12percent, p-cyanoaniline (A) 1percent, N-formyl-p-cyano-N-methylaniline (FA) 6percent, N,N'-dimethyl-N,N'-bis(p-cyanophenyl)hydrazine (H) 7percent, and CH2O 3percent) account for 100percent of p-cyanodimethylaniline moiety of NO, but ca. 40percent of the oxide oxygen of NO remains unaccounted for by product isolation.This is due to some loss of the catalyst and oxidation of the CH2Cl2 solvent during turnover.Oxidation of solvent results in the gradual exchange of the SbF6- axial ligand for Cl-.Product formation on reaction of NO with (TPPC2cap)FeIIISbF6 can be approximated by the first-order rate law.Since the observed first-order rate constants at a given i are a linear function of the iron(III) porphyrin, the reaction is first order in this catalyst and essentially so in NO.However, the finding that the initial rates are independent of i establishes that the iron(III) porphyrin catalyst is saturated with NO on initiation of the reaction.The exchange of Cl- for SbF6- axial ligand and some loss of catalyst during turnovers are responsible for the reactions changing from initial zero order to essentially first order in i.Trapping of the intermediate ((+.TPPC2cap)FeIVO) by the 2,4,6-tri-tert-butylphenol (TBPH), 2,3-dimethyl-2-butene (TME), and p-cyano-N-methylaniline (MA) prevents solvent oxidation and porphyrin oxidative destruction.Under these trapping conditions the reaction is rapid and zero order in NO to completion.That the zero-order kinetics are due to saturation of the 2cap)FeIII>+ catalysts by NO was established by following the time course of the reaction in the Soret and Q spectral regions.The products with TME are TME epoxide (100percent) and DA (100percent) while with TBPH the radical TBP. (100percent) and DA (100percent) are formed.The rate is also increased, but to a lesser extent, when using the poorer substrates, cyclohexene and norbornylene.These substrates also impart a zero-orderness to the appearance of products.The kinetics for the reaction of (TPPC2cap)FeIIISbF6 with NO using TME, TBPH, and MA as substrates have been computer simulated with the requirement of steady-state saturation in the intermediate (TPPC2cap)FeIIION.For successful simulations it is required that both the formation of (+.TPPC2cap)FeIVO + DA from (TPPC2cap)FeIIION and the reaction of (+.TPPC2cap)FeIVO with substrates (i.e., TME, TBPH, and MA) are partially rate limiting.At concentrations of added alkene less than that required for trapping of (+.TPPC2cap)FeIVO there are obtained, ...
Kinetics and Mechanisms of Oxygen Transfer in the Reaction of p-Cyano-N,N-Dimethylaniline N-Oxide with Metalloporphyrin Salts. 3. Catalysis by iron(III) Chloride
Dicken, C. Michael,Woon, T. C.,Bruice, Thomas C.
, p. 1636 - 1643 (2007/10/02)
Decomposition of p-cyano-N,N-dimethylaniline N-oxide (NO) catalyzed by iron(III) chloride ((Cl8TPP)FeIIICl) yields as products p-cyano-N,N-dimethylaniline (DA), p-cyano-N-methylaniline (MA), and formaldehyde (CH2Cl2 solvent, 25 deg C, N2 atmosphere).Intermediate in the reaction are mono and bis NO complexes (Cl8TPP(Cl)FeIIINO and Cl8TPP(NO)FeIIINO, respectively).Oxygen transfer from the complexed NO species to the iron porphyrin is rate-limiting and provides the higher valent iron(IV) salts (IVO>+. and IVO>+.) and DA.The observed kinetics for reactions involving 10-100 turnovers of catalyst dictate that the catalyst is saturated in the formation of Cl8TPP(Cl)FeIIINO and that formation of Cl8TPP(NO)FeIIINO is unfavorable.The two iron(IV)-oxo porphyrin ?-cation radical species are converted back to the iron(III) porphyrin catalytic moieties by oxidation of DA -> MA + CH2O and oxidation of CH2O.Addition of 2,4,6-tri-tert-butylphenol (TBPH), 2,3-dimethyl-2-butene (TME), and cyclohexene results in the formation of TBP. and the respective epoxides, thus inhibiting the oxidation of DA and CH2O.The kinetics of the overall reaction and formation of each product may be simulated by employing the reactions of Scheme II and eq l-r, and from the simulations, the rates and equilibria, leading to the formation of the two iron(IV)-oxo porphyrin ?-cation radical species may be determined as can minimal rate constants for the oxidations of DA, CH2O, and TBPH and the epoxidation of TME and cyclohexene.The results obtained herein with the electron-deficient porphyrin, (Cl8TPP)Fe(III)Cl, are discussed and compared to those obtained previously when employing (TPP)FeIIICl as the catalyst.
