56588-92-2Relevant academic research and scientific papers
Role of O- Ions in Charge-Transfer Reactions at the Surface of Silica-Supported Molybdenum Catalysts Prepared by the Grafting Method
Che, M.,Dyrek, K.,Louis, C.
, p. 4531 - 4535 (1985)
In order to elucidate the possible order of O- ions in charge-transfer processes, the reaction of adsorbed O- ions with electron acceptor molecules has been investigated on grafted Mo/SiO2 catalysts.It is shown that their high reactivity might explain the fact that O- cannot be detected in charge-transfer reactions on oxide surfaces between acceptor molecules (A) and surface oxygen in low coordination (OLC2-) A + OLC2- -> O- + A-.Tetracyanoethylene (TCNE) readily reacts with adsorbed O- ions to form a new intermediate species (g = 2.003, doublet with aH = 50 +/- 1 G).The hyperfine splitting and experiments performed with various molecules suggest that TCNE undergoes successive reactions with adsorbed O- species and OH- surface ions to lead to the formation of an intermediate species assumed to be (CN)-CH=C.(CN) (aH is the coupling constant between the unpaired electron and the proton located trans to it on the β carbon).This species is stable at room temperature, but can react in the presence of excess TCNE and lead to the formation of TCNE- radical.The reaction between fumaronitrile H(CN)=(CN)H and adsorbed O- ions induces the same doublet with the same coupling constant and confirms the identification of the intermediate species observed with TCNE.It further indicates that the proton is more easily abstracted by O- than the CN group.This work also shows that on reduced Mo/SiO2 catalysts, the Mo5+ ions act as electron donor centers while on the oxidized catalysts, the surface O2- ions do not lead to charge-transfer reactions with TCNE.
Photoinduced Electron Transfer from Triplet Fullerene, 3C60, to Tetracyanoethylene. Fourier Transform Electron Paramagnetic Resonance Study
Michaeli, S.,Meiklyar, V.,Schulz, M.,Moebius, K.,Levanon, H.
, p. 7444 - 7447 (1994)
Fourier transform EPR spectroscopy was employed in studying the electron transfer (ET) and the quenching mechanisms of the photoexcited triplet state of C60 (electron donor) in the presence of the electron acceptor tetracyanoethylene (TCNE) in a benzonitrile solution.The ET reaction product, which is the stable anion radical TCNE, interacts with 3C60 (both detected by EPR in the liquid phase), leading to chemically induced dynamic electron polarization of TCNE, via triplet-doublet mixing mechanism.
Free Energy Dependence of the Intrinsic Rate of Electron Transfer in Diffusional Quenching of trans-Stilbene S1 by Electron-Deficient Olefins
Angel, Stephen A.,Peters, Kevin S.
, p. 3606 - 3612 (2007/10/02)
The quenching of the first excited singlet states of trans-stilbene and 4,4'-dimethyl-trans-stilbene by acrylonitrile, fumaronitrile, and tetracyanoethylene has been examined by picosecond laser spectroscopy.The intrinsic rate constant of electron transfer is separated from the diffusion rate constant by applying the Collins and Kimball formalism for time-dependent rate constants.The intrinsic rates of electron transfer are correlated with the free energy changes for electron transfer, and it is found that the correlation does not follow the predictions of Marcus' adiabatic electron-transfer theory.
Gas-phase ligand substitution reactions with the 17-electron transition-metal complexes (OC)4Fe.-, (OC)5Cr.-, and (OC)4MnH.-
McDonald, Richard N.,Schell, Philip L.
, p. 1820 - 1827 (2008/10/08)
Three transition-metal complex negative ions, (OC)4Fe.-, (OC)5Cr.-, and (OC)4MnH.-, were generated and studied in ligand substitution reactions with a variety of neutral ligand substrates. Only (OC)4Fe.- reacted with PF3 and gave sequentially the product ions (OC)4-xFe(PF3)x.- where x = 1-3. The three metal complex negative ions formed ligand substitution product anions with NO; the reaction with (OC)4MnH.- also produced some of the corresponding adduct anion. With SO2, (OC)4Fe.- gave only ligand substitution, (OC)5Cr.- formed a mixture of the adduct and the product of ligand substitution, and (OC)4MnH.- produced only the adduct. Both the NO and SO2 reactions were believed to occur by the associative mechanism with the SO2 reactions proceeding via Lewis acid-base complexes. Only (NC)2C=C(CN)2 (TCNE) of the seven olefins examined reacted with the metal complex negative ions forming the product of electron transfer (TCNE.-) as well as the product ions of ligand substitution. The reactions of all three metal complex negative ions with (CF3)2C=O and of (OC)5Cr.- with biacetyl were considered to involve initial electron transfer within the orbiting collision complex. The reaction of (OC)4MnH.- with O2 produced various oxidation products, the most noteworthy being HCO2- as a major product anion. This latter result is considered to be evidence for the migratory insertion reaction, OC-Mn-H ? Mn-CHO, in the adduct formed from (OC)4MnH.- with O2.
Gas-phase ligand substitution reactions with (OC)Fe(NO)2.-', (OC)2Co(NO).-, (η3-C3H5)Co(CO)2.-, (C3H5)Co(CO)3.-, and CpCo(CO)2.-
McDonald, Richard N.,Schell, Philip L.
, p. 1806 - 1820 (2008/10/08)
Three 17-electron transition-metal complex negative ions LM(CO)x-1.- ((OC)Fe(NO)2.-, (OC)2Co(NO).-, and (η3-C3H5)Co(CO)2.-) and two parent molecular anion radicals LM(CO)x.- ((C3H5)Co(CO)3.- and CpCo(CO)2.-) were generated by electron impact on the corresponding LM(CO)x complexes in the gas phase. The ion-molecule reactions of these five metal complex negative ions were studied with the neutral molecules PF3, PMe3, NO, SO2, olefins with electron-donating and -withdrawing vinyl substituents, acetone and certain fluorinated derivatives, biacetyl, O2, CO, and CS2. In general, the LM(CO)x-1.- complexes and CpCo(CO)2.- reacted by ligand substitution involving the associative mechanism. In many cases, the product ions of adduct formation and ligand substitution were directly observed in the same reaction. These ligand substitution reactions appear to take advantage of the abbility of the NO, η3-C3H5, and Cp ligands to reduce their hapticities as the neutral ligand bonds to the metal. The reaction of (C3H5)Co(CO)3.- with PF3 occurred by fragmentation of the allyl radical. This latter result was considered to occur by radical β-fragmentation of the excited acyl complex [C3H5C(=O)Co(CO)2(PF3) .-]* formed by CO insertion into the Co-allyl bond. Both parent molecular anion radicals were observed to undergo electron transfer with several of the neutral substrates yielding EA((η3-C3H5)Co(CO)3) = EA(CpCo(CO)2) = 0.62 ± 0.1 eV; EA(η3-C3H5)Co(CO)2) = 0.9 ± 0.2 eV was also measured. The results of the reactions of the parent LM(CO)x.- species with the neutral ligands were consistent with their structures having a 17-electron configuration about the metal with η3-Cp and η1-C3H5 ligands.
Electron Affinities of Di- and Tetracyanoethylene and Cyanobenzenes Based on Measurements of Gas-Phase Electron-Transfer Equilibria
Chowdhury, Swapan,Kebarle, Paul
, p. 5453 - 5459 (2007/10/02)
The electron affinities of tetracyanoethylene, trans-1,2-dicyanoethylene, and eleven substituted benzonitriles as well as two naphthonitriles were determined by measurement of the electron-transfer equilibria A-+B=A+B- with a pulsed electron high ion source pressure mass spectrometer.Rate constants for exothermic electron transfer involving the cyano compounds were found to be near unit collision efficiency.The EA (tetracyanoethylene)=3.17 eV obtained in the present work is considerably higher than the 2.3 eV photodetachment value of Palmer and Lyons.The electron affinities of benzene and benzonitrile substituted by CN, CHO, and NO2 increase in the given order, while the order for nitrobenzene is CHO, CN, NO2.This reversal of order is explained on the basis of a larger attenuation of the ?-withdrawing effect relative to the field effect of substituents when the electron density in the ?* single-electron orbital is decreased.
On the Reaction of Chloranil with Cyanide Ions - an ESR Study
Rehorek, Detlef,Janzen, Edward G.
, p. 705 - 717 (2007/10/02)
The reaction of chloranil 1 with cyanide ions in acetonitrile and methanol solutions has been studied.The ESR spectra revealed the formation of semiquinone anion radicals 7, 8, and 9.The latter has been found as its protonated form in methanol only.In addition, both 1 and 2,3-dicyano-5,6-dichloro-1,4-benzoquinone 4 gave tetracyanoethylene anion radicals 6 upon reaction with cyanide ions in acetonitrile.Using 13C-labelled cyanide 6 was shown to originate from the fragmentation of the cyanide addition product to 4.Using the spin trapping technique it was found that no cyanyl free radicals are formed during the thermal reaction of either 1 or 4 with cyanide ions.
Effects of Base on Oxidation of an NADH Model Compound by Iron(III) Complexes and Tetracyanoethylene
Fukuzumi, Shunichi,Kondo, Yuji,Tanaka,Toshio
, p. 673 - 680 (2007/10/02)
Effects of base on both an electron-transfer reaction from an NADH model compound, 1-benzyl-1,4-dihydronicotinamide (BNAH) to (3+) (N-N = 2,2'-bipyridine and 1,10-phenanthroline) and a hydride transfer from BNAH to tetracyanoethylene (TCNE) in acetonitrile have been examined.The stoicheiometry of the electron transfer from BNAH to (3+) in the absence of a base indicates that BNAH is a one-electron donor.In the presence of a base, however, BNAH acts as an apparent two-electron donor, when the two-electron transfer proceeds via a multistep process; a fast one-electron transfer from BNAH to (3+) occurred, followed by the rate-determining deprotonation of BNAH+. by base and the subsequent fast electron transfer from BNA. to (3+).The rate constants for the proton transfer from BNAH+. to a series of pyridine derivatives have been determined.In the reduction of TCNE by BNAH, BNAH appears to be a two-electron donor in both the absence and presence of a base.Rates of the reduction of TCNE by BNAH increased with inceasing base concentration, suggesting the involvement of BNAH+. as an intermediate in the hydride transfer from BNAH to TCNE.The kinetic analyses have led to the evaluation of the proton transfer rate constants for the deprotonation of BNAH+. with various bases, which accord with those obtained from the electron-transfer reactions of BNAH with (3+) in the presence of bases.Based on the Broensted plot of the proton transfer rate constants as well as the variation of the primary kinetic isotope effects kH/kD with the pKa of the base, the pKa value for BNAH+. has been evaluated as 3.6 +/-0.4.
Thiacyanocarbons. 5. Reactions of Tetracyano-1,4-dithiin and Tetracyanothiophene with Nucleophiles: Synthesis of Tetracyanopyrrole and Tetracyanocyclopentadiene Salts
Simmons, H. E.,Vest, R. D.,Vladuchick, S. A.,Webster, O. W.
, p. 5113 - 5121 (2007/10/02)
Reactions at the double bonds of tetracyano-1,4-dithiin and tetracyanothiophene have been explored.Generally, nucleophiles attack the dithiin by an addition-elimination mechanism to produce divinyl sulfides.The resulting anions are stable, experience fragmentation, or undergo further condensation reactions to produce heterocyclic structures.For example, tetracyano-1,4-dithiin is converted by thiocyanate ion to a thiophenopyrimidine.In fragmentation reactions, the dithiin acts as a masked maleonitrile and as such is useful for the synthesis of tetracyanoethylene.Remarkably, the dithiin reacts with sodium azide to give tetracyanopyrrole and with reactive methyl compounds to give substituted tetracyanocyclopentadienide ions.Tetracyanothiophene reacts with nucleophiles in a manner similar to tetracyanodithiin but at higher temperatures.
