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Showing papers on "Homolysis published in 1991"


Journal ArticleDOI
TL;DR: In this article, the pyrolysis of TVSb was investigated in a flow tube reactor using Dz and He carrier gases, and it was shown that the activation energy for pyrolynsis is less than the expected Sb-vinyl bond strength.
Abstract: The pyrolysis of TVSb has been investigated in a flow tube reactor using Dz and He carrier gases. For TVSb alone, the most likely pyrolysis reaction involves an Sbcentered reductive elimination pathway. A less likely possibility is pyrolysis via homolysis of the Sb-C bonds, yielding vinyl radicals. Unfortunately, examination of the organic byproducts in both He and D, yields insufficient information to form a definitive hypothesis. However, in He the pyrolysis rate for TVSb is more rapid than for TMSb. Since vinyl radicals form stronger bonds than methyl radicals, this datum contradicts the Sb-C bond homolysis mechanism. Again, the activation energy for pyrolysis is less than the expected Sb-vinyl bond strength. Finally, the addition of C7D, produces no CH,=CHD, indicative of the absence of vinyl radicals. To elucidate our understanding of GaSb growth by using TMGa and TVSb, the pyrolysis rates for this combination of reactants were also studied. CH, radicals from (CH3N), pyrolysis were found to enhance TVSb pyrolysis in He. TMGa also increases the TVSb pyrolysis rate, mainly due to the methyl radicals produced. A heterogeneous pyrolysis reaction appears a t high surface area. At V/III ratios normally used for OMVPE growth, carbonaceous deposits were formed. Thus, TVSb may be a useful precursor for OMVPE only a t V/III ratios less than unity.

551 citations


Journal ArticleDOI
TL;DR: In this paper, the acidities of 35 phenoxyl radical cations were estimated from pK HA, E ox (A − ), and E ox(HA) values over a range of greater than 40 kcal/mol.
Abstract: Oxidation potentials for 35 phenoxide ions and 3 naphthoxide ions have been combined with their pK HA values to estimated homolytic bond dissociation energies (BDEs) for the O-H bonds in phenols. Comparison with literature values shows that there is remarkably good agreement ΔBDE values determined by different methods. A good correlation of E ox (A − ) values for p-GC 6 H 4 O − phenoxide ions with σ + constants was observed over a range of greater than 40 kcal/mol. The acidities of 35 phenoxyl radical cations have been estimated from pK HA , E ox (A − ), and E ox (HA) values. A good correlation of E ox (HA) vs pK HA •+ was observed from m-GC 6 H 4 OH •+ radical cations, but the points for para donors were found to deviate from the line

401 citations


Journal ArticleDOI
TL;DR: In this article, a two-phase system for monoacylation of α-keto acids by persulfate was proposed, which takes advantage of the difference in basicity and lipophilicity between the starting base and the mono-acylation products.
Abstract: The silver-catalyzed decarboxylation of α-keto acids by persulfate leads to acyl radicals, which can effect the selective homolytic acylation of pyridine and pyrazine derivatives. Compared with the previously developed source of acyl radicals by hydrogen abstraction from aldehydes, this procedure is more effective in monoacylation when multiple positions of high nucleophilic reactivity are available in the heterocyclic ring. Although the introduction of an acyl group strongly activates the heterocyclic ring toward further substitution, monoacylation can be achieved by taking advantage of the difference in basicity and lipophilicity between the starting base and the monoacylation products in a two-phase system

186 citations



Journal ArticleDOI
TL;DR: In this article, the rates of decarboxylation were estimated for the acyloxy radicals formed in the photolysis of substituted 1-naphthylmethyl alkanoates based on a mechanism involving initial carbon-oxygen homolytic bond cleavage from the excited singlet state.
Abstract: Rates of decarboxylation (k CO2 R ) have been estimated for the acyloxy radicals formed in the photolysis of substituted 1-naphthylmethyl alkanoates. These rates are based on a proposed mechanism involving initial carbon-oxygen homolytic bond cleavage from the excited singlet state. The products are formed by two competing pathways: electron transfer in the radical pair to give an ion pair and decarboxylation. Measured product yields along with an estimate of the electron-transfer rate (k ET ) allow calculation of k CO2 R as a function of R. The values obtained are the following (R, k (10 9 s −1 )): CH 3 , <1.3; CH 3 CH 2 , 2.0; (CH 3 ) 2 CH, 6.5; (CH 3 ) 3 C, 11; PhCH 2 , 5.0; PhCH 2 CH 2 , 2.3

127 citations


Journal ArticleDOI
TL;DR: In this paper, a series of nitrate esters were measured for thermal decompositin and solvent rate effects, and the alkoxy radicals formed by homolysis together with some of their further degradation products were stabilized by hydrogen donation.
Abstract: Rates of thermal decompositin and solvent rate effects have been measured for a series of nitrate esters. The alkoxy radicals formed by homolysis together with some of their further degradation products have been stabilized by hydrogen donation. Internal and external return of nitrogen dioxide have been demonstrated by solvent cage effects and isotope exchange. Radical-stabilizeing substituents favor β-scission. Dinitrates in a 1,5 relationship behave as isolated mononitrates. Dinitrates in a 1,3 or 1,4 relationship exhibit intramolecular reactions. Tertiary nitrate esters in diethyl ether undergo elimination rather than homolyisis

109 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that 1-phenyl-2-(phenylthio)vinyl radicals can exhibit homolytic intramolecular cyclization reactions, leading to benzothiophene products to a comparatively much greater extent than the 1-alkyl- 2-substituted analogues.
Abstract: Reaction of benzenethiol at 100 °C with neat alkyl- and dialkyl-acetylenes leads to virtually quantitative formation of isomeric mixtures of (E)- and (Z)-vinyl sulphide adducts in ratios which depend largely upon both the extent and the nature of alkyl substitution. Results are explained in terms of rapidly interconverting sp2-hybridized (E)- and (Z)-1-alkyl-2-(phenylthio)vinyl radical intermediates which can undergo hydrogen transfer from benzenethiol to an extent which is essentially dependent upon the steric hindrance of their cis-2-substituent. Consistent results are provided by related radical reactions of diphenyl disulphide with alkyl-substituted alkynes to afford varying amounts of 1,2-bis(phenylthio)ethylene adducts ascribable to SH2 reaction of the resulting 1-alkyl-2-(phenylthio)vinyl radicals with the disulphide present. Under analogous conditions benzenethiol and diphenyl disulphide react with phenylacetylenes to give vinyl sulphide or bissulphide adducts in a trans-stereoselective fashion. The findings are interpreted by suggesting, for the intermediate sp-hybridized 1-phenyl-2-(phenylthio)vinyl radicals, the occurrence of significant bonding interaction between the unpaired electron and the adjacent sulphur, which would essentially prevent attack of radical scavenger on the side cis to PhS. Evidence is also presented that 1-phenyl-2-(phenylthio)vinyl radicals can exhibit homolytic intramolecular cyclization reactions, leading to benzothiophene products to a comparatively much greater extent than the 1-alkyl-2-substituted analogues; however, 1-tert-butyl-2-(phenylthio)vinyl radical would represent a special case.

78 citations


Journal ArticleDOI
TL;DR: In this article, the homolytic bond dissociation energies of ZnO and Zn+ with nitrogen dioxide were determined by using guided ion-beam mass spectrometry to measure the kinetic energy dependence of the endothermic reactions, and the data were interpreted to yield the bond energy for ZnOs, D^0_0=1.61±0.04 eV, a value considerably lower than previous experimental values, but in much better agreement with theoretical calculations.
Abstract: The homolytic bond dissociation energies of ZnO and ZnO^+ have been determined by using guided ion‐beam mass spectrometry to measure the kinetic‐energy dependence of the endothermic reactions of Zn^+ with nitrogen dioxide. The data are interpreted to yield the bond energy for ZnO, D^0_0=1.61±0.04 eV, a value considerably lower than previous experimental values, but in much better agreement with theoretical calculations. We also obtain D^0_0(ZnO^+)=1.67±0.05 eV, in good agreement with previous results. Other thermochemistry derived in this study is D^0_0(Zn^+–NO)=0.79±0.10 eV and the ionization energies, IE(ZnO)=9.34±0.02 eV and IE(NO_2)=9.57±0.04 eV.

75 citations


Journal ArticleDOI
TL;DR: In this article, the trialkyl-silanethiol couple was used as a polarity reversal catalyst to transfer hydrogen-atom transfer from the Si-H group of the silane to the alkyl radical R˙.
Abstract: Saturated primary, secondary and tertiary alkyl halides RX (X = Cl, Br or I) are reduced to the corresponding alkanes RH in essentially quantitative yield by triethylsilane in refluxing hexane or cyclohexane in the presence of a suitable initiator and an alkanethiol catalyst. Reduction proceeds by a radical chain mechanism and the thiol acts as a polarity reversal catalyst which mediates hydrogen-atom transfer from the Si–H group of the silane to the alkyl radical R˙. Triphenylsilanethiol and perfluorohexanesulphenyl chloride are also effective catalysts; the latter is probably reduced in situ to the corresponding fluorinated thiol. Other silanes R3SiH (R = Prn, Pri or Ph) also bring about reduction. The silane–thiol couple therefore serves as a useful replacement for tributylstannane as a homolytic reducing agent for alkyl halides. Reduction of 6-bromohex-1-ene, to give a mixture of hex-1-ene and methylcyclopentane, is more sluggush than reduction of saturated halides and this is attributed to removal of the thiol catalyst by addition across the CC bond. Ethyl 4-bromobutanoate is smoothly reduced to ethyl butanoate without interference from the ester function. Dialkyl sulphides are reduced to alkanes by triethylsilane in a radical chain reaction, but the effect of added thiol depends on the nature of the S-alkyl groups in the sulphide. The trialkylsilanethiol couple can also successfully replace trialkylstannane as the reducing agent in the Barton–McCombie deoxygenation of primary and secondary alcohols via their S-methyl dithiocarbonate (xanthate) esters. Good yields of deoxy compounds are obtained from octan-1-ol, octan-2-ol, octadecan-1-ol, 5α-cholestan-3β-ol, cholesterol and 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose.

74 citations


Journal ArticleDOI
TL;DR: The •OH radical reaction with exo-2-amino-endo-6-(methylthio)bicyclo[2.1]heptane-endomino-carboxylic acid primarily affords oxidation of the sulfur center in the molecule as mentioned in this paper.
Abstract: The •OH radical reaction with exo-2-amino-endo-6-(methylthio)bicyclo[2.2.1]heptane-endo-2-carboxylic acid primarily affords oxidation of the sulfur center in the molecule. The subsequent pathway strongly depends on pH. A transient radical with interaction between the sulfur and the carboxylate moieties is stabilized particularly in acid solutions with maximum yield at pH 3. The underlying mechanism is considered to be a concerted action involving an electron transfer from the anionic carboxylate to the oxidized sulfur atom, homolytic carbon-carboxyl bond breakage, and deprotonation of the amino group. Related studies indicate that this kind of radical-induced decarboxylation can be generalized and receives its driving force to a significant extent from the resonance stabilization of the α-amino radical remaining after CO 2 cleavage

73 citations


Journal ArticleDOI
TL;DR: In this article, the homolytic bond dissociation energy of the titanium neutral hydride D0(Ti−H) was determined experimentally for the first time by using guided ion beam tandem mass spectrometry to measure the kinetic energy dependence of the endothermic hydrides abstraction reactions of Ti+ with methylamine, dimethylamine and trimethylamines.
Abstract: The homolytic bond dissociation energy of the titanium neutral hydride D0(Ti–H) is determined experimentally for the first time by using guided ion beam tandem mass spectrometry to measure the kinetic energy dependence of the endothermic hydride abstraction reactions of Ti+ with methylamine, dimethylamine, and trimethylamine. From the thresholds of these reactions, the value of D0(Ti–H)=2.12±0.09 eV (48.9±2.1 kcal/mol) at 298 K is derived. Other 298 K thermodynamic values obtained are D0(Ti+–H−)=8.19±0.09 eV (188.8±2.1 kcal/mol), I.E.(TiH)=6.59±0.14 eV, P.A.(Ti−)=15.64±0.09 eV (360.6±2.1 kcal/mol), and ΔfH(TiH)=116.4±2.3 kcal/mol. This thermochemistry is compared with theoretical values and its relationship to hydride bond energies for the other first row transition metals is discussed.

Journal ArticleDOI
TL;DR: The reason for this instability appears to lie in excessive homolytic dissociation of H 2 O 2 with consequent rapid attack at the porphyrin β-position.

Journal ArticleDOI
TL;DR: In this article, the acidity and homolytic bond dissociation energies of diphenylmethanes, including 9-G-fluorenes and Ph 2 CHG, were investigated.
Abstract: The acidities and homolytic bond dissociation energies (BDEs) of the acidic H-C or H-N bonds in six α-substituted diphenylmethanes, Ph 2 CHG, nine remotely substituted diphenylamines, four bridged diphenylamines (iminodibenzyl, iminostilbene, phenothiazine, phenoxazine), three carbazoles, indole, and pyrrole are reported. The near constancy of the increased acidity for 9-G-fluorenes compared to α-G-diphenylmethanes, which represents the approximate relative aromatic stabilization energies of the fluorenide anions, indicates that electronic effects on 9-GFl − and Ph 2 CG − ions do not differ greatly. On the other hand, steric effects in Ph 2 CG • radicals cause destabilizing effects when G is SPh, CO 2 Et, or SO 2 Ph, whereas, except for SO 2 Ph, these functions are stabilizing in 9-GFl • radicals

Journal ArticleDOI
TL;DR: In this paper, a homolysis of the CH 3 ReO 3 bond was shown to occur by outer-sphere back electron transfer or atom abstraction by the methyl radical.


Journal ArticleDOI
TL;DR: In this article, the electrophilic radicals R • =p-O 2 NC 6 H 4 CH 2 • or Me 2 C(NO 2 ) • add readily to CH 2 =C(NMe 2 ) 2 to yield RCH 2 C NMe 2 2 •, which undergoes electron transfer with p-O2 NC 6H 4 CH2 Cl or Me2 C( NO 2 )• to regenerate R •, while the N-pyrrolidino-1-cycloalkenes are more reactive toward p-nitrobenzyl
Abstract: The electrophilic radicals R • =p-O 2 NC 6 H 4 CH 2 • or Me 2 C(NO 2 ) • add readily to CH 2 =C(NMe 2 ) 2 to yield RCH 2 C(NMe 2 ) 2 • , which undergoes electron transfer with p-O 2 NC 6 H 4 CH 2 Cl or Me 2 C(NO 2 ) 2 to regenerate R • . Hydrolysis yields p-O 2 NC 6 H 4 CH 2 CONMe 2 and Me 2 C=CHC(NMe 2 ) 2 + , respectively. p-Nitrobenzyl radicals add readily to N-pyrrolidino- or N-morpholino-1-cycloalkenes to yield after hydrolysis the α-(p-nitrobenzyl)cycloalkanones. Photostimulated alkylation of N-pyrrolidino-1-cycloalkenes by Me 2 C(NO 2 ) 2 is not observed although in competitive reactions between the enamine and Me 2 C=NO 2 Li, the product from attack of Me 2 C(NO 2 ) • upon the enamine double bond is formed. The N-pyrrolidino-1-cycloalkenes are more reactive toward p-O 2 NC 6 H 5 CH 2 . •than their morpholino analogues

Journal ArticleDOI
TL;DR: In this article, the pyrolysis of TVSb was investigated in a flow tube reactor using Dz and He carrier gases, and it was shown that the activation energy for pyrolynsis is less than the expected Sb-vinyl bond strength.
Abstract: The pyrolysis of TVSb has been investigated in a flow tube reactor using Dz and He carrier gases. For TVSb alone, the most likely pyrolysis reaction involves an Sbcentered reductive elimination pathway. A less likely possibility is pyrolysis via homolysis of the Sb-C bonds, yielding vinyl radicals. Unfortunately, examination of the organic byproducts in both He and D, yields insufficient information to form a definitive hypothesis. However, in He the pyrolysis rate for TVSb is more rapid than for TMSb. Since vinyl radicals form stronger bonds than methyl radicals, this datum contradicts the Sb-C bond homolysis mechanism. Again, the activation energy for pyrolysis is less than the expected Sb-vinyl bond strength. Finally, the addition of C7D, produces no CH,=CHD, indicative of the absence of vinyl radicals. To elucidate our understanding of GaSb growth by using TMGa and TVSb, the pyrolysis rates for this combination of reactants were also studied. CH, radicals from (CH3N), pyrolysis were found to enhance TVSb pyrolysis in He. TMGa also increases the TVSb pyrolysis rate, mainly due to the methyl radicals produced. A heterogeneous pyrolysis reaction appears a t high surface area. At V/III ratios normally used for OMVPE growth, carbonaceous deposits were formed. Thus, TVSb may be a useful precursor for OMVPE only a t V/III ratios less than unity.

Journal ArticleDOI
TL;DR: The isomerization of 1,2-epcxycyclopentane (1) to enantiomerically enriched (R)-cyclopent-2-enol (2) in protic solvents is catalyzed by cob(I)alamin this article.
Abstract: The isomerization of 1,2-epcxycyclopentane (1) to enantiomerically enriched (R)-cyclopent-2-enol (2) in protic solvents is catalyzed by cob(I)alamin. The enantiomeric excess (e.e.) of (R)-2 is usually ca. 60%; it is only slightly dependent on the temperature, but increases with decreasing dielectric constant e of the solvent. Standard kinetic methods show the reaction to be first order in vitamin B12 and zero order in 1. The rate constant increases exponentially with increasing e of the solvent. An Arrhenius plot at e = 40 gives activation parameters ΔH≠ = 78 ± 4 kJ·mol−1 and ΔS≠ = −49 ± 1 J·mol−1·K−1. The isomerization 1 → 2 proceeds in two steps (Schemes 2 and 7): (i) The epoxide ring is first opened by the proton-assisted fast and irreversible nucleophilic attack of the chiral CoI catalyst to form diastereoisomeric (1R,2R)- and (1S,2S)-(2-hydroxycyclo-pentyl)cob(III)alamins 6 in a ratio of ca. 4:1 which are the dominant species in the steady state; (ii) The intermediates 6 then decompose in the rate-limiting step to form 2 and recycled catalyst. Experiments with specifically 2H-labeled 1 showed the hydro-cobalt elimination 6 → 2 to be non-stereoselective. It proceeds via reversible CoC bond homolysis to a free 2-hydroxycyclopentyl radical from which stereoelectronically controlled H-abstraction by Co11 takes place.

Journal ArticleDOI
TL;DR: In aqueous acetonitrile the ion pairs are solvent separated and photolysis gives substantial amounts of 2-, 3-, and 4-iodobiphenyls, in addition to iodobenzene, by an initial heterolytic cleavage as mentioned in this paper.
Abstract: Diphenyliodonium halides exist as tight ion pairs in acetonitrile, and photolysis gives almost exclusively iodobenzene by a homolytic cleavage reaction from a charge transfer excited state, whereas in aqueous acetonitrile the ion pairs are solvent separated and photolysis gives substantial amounts of 2-, 3-, and 4-iodobiphenyls, in addition to iodobenzene, by an initial heterolytic cleavage

Journal ArticleDOI
TL;DR: In this paper, the acidities of 35 phenoxyl radical cations were estimated from pK HA, E ox (A − ), and E ox(HA) values over a range of greater than 40 kcal/mol.
Abstract: Oxidation potentials for 35 phenoxide ions and 3 naphthoxide ions have been combined with their pK HA values to estimated homolytic bond dissociation energies (BDEs) for the O-H bonds in phenols. Comparison with literature values shows that there is remarkably good agreement ΔBDE values determined by different methods. A good correlation of E ox (A − ) values for p-GC 6 H 4 O − phenoxide ions with σ + constants was observed over a range of greater than 40 kcal/mol. The acidities of 35 phenoxyl radical cations have been estimated from pK HA , E ox (A − ), and E ox (HA) values. A good correlation of E ox (HA) vs pK HA •+ was observed from m-GC 6 H 4 OH •+ radical cations, but the points for para donors were found to deviate from the line

Journal ArticleDOI
TL;DR: In this paper, free-radical additions of methylene dichloride and chloroform to various peroxidic compounds having unsaturation δ to the peroxide bond and a substituent on the chain linking both functions gave five-membered heterocycles with some stereoselectivity.
Abstract: Free-radical additions of methylene dichloride and chloroform to various peroxidic compounds having unsaturation δ to the peroxidic bond and a substituent on the chain linking both functions gave five-membered heterocycles with some stereoselectivity. The influence of various structural factors such as the size of the substituent, the nature of the peroxidic function (peroxide, perester and percarbonate), etc. have been studied.

Journal ArticleDOI
TL;DR: In the presence of alkyl halides, C-centered radicals can be trapped by alkenes and yields saturated and/or unsaturated addition products as discussed by the authors, but no reaction occurs using octacarbonyldicobalt.
Abstract: Irradiation of dicarbonyl(η5-cyclopentadienyl)iron dimer 1 or decacarbonyldimanganese (2) in the presence of alkyl halides leads to C-centered radicals which can be trappedby alkenes and yields saturated and/or unsaturated addition products. Carbon radicals are generated via halogen abstraction by the initially formed metal-centered radicals resulting from homolysis of the metal-metal bond of dimeric mediators 1 and 2. No reaction occurs using octacarbonyldicobalt (3).


Journal ArticleDOI
TL;DR: In this article, the pyrolysis of triisopropylantimony ((C3H7)3Sb) and triallylantimony (C 3H5)3sb) was investigated in He and D2 using a SiO2 flow tube reactor at atmospheric pressure.
Abstract: The pyrolysis of triisopropylantimony ((C3H7)3Sb) and triallylantimony ((C3H5)3Sb) has been investigated mass-spectrometrically in He and D2 using a SiO2 flow tube reactor at atmospheric pressure. Both temperature and time dependencies of percent decomposition were studied and the reaction products were analyzed. The overall decomposition processes for both compounds were found to be homogeneous and first order. (C3H7)3Sb pyrolyzes at 250-350° C with no effect of the ambient gas. However, C3H6, C3H8, and C6H14 (2,3-dimethylbutane) were produced in He whereas C3H3D appeared in D2. The pyrolysis is believed to begin via bond cleavage to generate the free C3H7 radicals that, in turn, recombine and disproportionate. Isopropyl radicals react slowly with D2, producing the C3H7D detected. For (C3H5)3Sb, the pyrolysis takes place at 100-160° C. The only major product is C6H10 (1,5-hexadiene). Both the pyrolysis rate and products were independent of the ambient. Two possible mechanisms, homolysis and reductive coupling, are discussed. Assuming that homolysis is the rate-limiting step for the pyrolysis of both (C3H7)3Sb and (C3H5)3Sb, bond strengths of 30.8 and 21.6 kcal/mole for C3H7—Sb and C3H6—Sb were determined from the experimental data. When either (C3H7)3Sb or (C3H5)3Sb was mixed with trimethylindium, a nonvolatile, liquid material, probably an adduct, was formed.

Journal ArticleDOI
TL;DR: In this paper, photolysis of permethylated linear polygermanes, Me(Me2Ge)nMe (n = 3-6), proceeds by both the contraction of the chain with loss of dimethylgermylene and the homolytic scission of germanium-germanium bond.
Abstract: Photolysis of permethylated linear polygermanes, Me(Me2Ge)nMe (n = 3–6), proceeds by both the contraction of the chain with loss of dimethylgermylene and the homolytic scission of germanium-germanium bond.

Journal ArticleDOI
TL;DR: In this article, the homolytic methylation of naphthoquinone to obtain menadione has been investigated by three sources of methyl radical: t-BuOOH DMSO and H 2 O 2 acetone and H2 O 2.

Journal ArticleDOI
TL;DR: In this paper, a 3: 1 mixture of 2,2-dimethylbutane and tert-butylbenzene was found to work well at temperatures below 70 K.
Abstract: The photochemistry of a number of metalloporphyrin oxoanion complexes has been examined by matrix isolation techniques, using both frozen solvent glasses and polymer films. After an extensive search for a noncoordinating, unreactive, glassing solvent, a 3: 1 mixture of 2,2-dimethylbutane and tert-butylbenzene was found to work well at temperatures below 70 K. Alternatively, the photochemistry of metalloporphyrins was monitored in polymer films by the evaporation on a sapphire window of metalloporphyrin solutions in toluene containing either pol: :methyl methacrylate) or poly(a-methylstyrene). The polymer films have the added advantage of a greatly increased temperature range, providing diffusional isolation even at room temperature. The photoreduction of the metal by homolytic a-bond cleavage and loss of the axial ligand appears to be a general mechanism for all metalloporphyrin complexes examined. The formation of metal-oxo species from photolysis of metalloporphyrin oxoanion complexes in solution derives from secondary, thermal reactions. The role of metalloporphyrins in two very separate biological processes, oxoanion reduction (nitrite and sulfite reductases)l-" and hydrocarbon oxidation (cytochrome P450),s has led us to examine the photochemistry of metalloporphyrin complexes6 of a number of anions including nitrate and nitrite,' sulfate and bisulfate,' perchlorate,* and ~hloride.~ The photochemistry of porphyrins1&14 and metall~porphyrins~~,'~~~ continues to com- mand substantial interest. In this area, one of the more surprising observations is 8-bond cleavage in the solution photochemistry of metalloporphyrin oxoanion complexes;" this results in oxygen atom transfer to form metal-oxo complexes and can occur with either homolytic or heterolytic transfer.


Journal ArticleDOI
TL;DR: In this article, a combination of gas chromatography and mmasa spectroscopy was used to investigate the pyrolytic decomposition of tellurium-carbon bond homolysis.