Two-electron reductive reactivity of trivalent uranium tetraphenylborate complexes of (C5Me5) and (C5Me4H)

The reductive reactivity of the (BPh₄)¹⁻ ligand in pentamethylcyclopentadienyl [(C₅Me₅)₂U][(μ-η²:η¹-Ph)₂BPh₂] (1) was compared with that of the tetramethyl analog, [(C₅Me₄H)₂U][(μ-η⁶:η¹-Ph)(μ-η¹:η¹-Ph)BPh₂] (2) using PhSSPh as a probe to determine if the mode of (BPh₄)¹⁻ bonding affected the reduction. Both complexes act as two-electron reductants to form (C₅Me₄R)₂U(SPh)₂ [R = Me, 3; H, 4], but only in the R = H case could the product be crystallographically characterized. An improved synthesis of 1 from [(C₅Me₅)₂UH]₂ (5) and [Et₃NH][BPh₄] is also reported as well as its reaction with MeCN that provides another route to the unusual, parallel-ring, uranium metallocene [(C₅Me₅)₂U(NCMe)₅][BPh₄]₂ (6).     

Synthesis, characterization, and X-ray crystal structure of the octabromodiosmate(III) salt [(C5Me4H)2OsBr]2[Os2Br8] and its conversion to [(C5Me4H)2OsBr][Os2HBr4(cod)2]

Treatment of hexabromoosmic acid, H₂OsBr₆, with 4 equiv. of tetramethylcyclopentadiene (C₅Me₄H₂) in tert-butanol at reflux for 8 h affords the unusual salt [(C₅Me₄H)₂OsBr]₂[Os₂Br₈], 1, which is the bis(tetramethylcyclopentadienyl)bromoosmocinium(IV) salt of the octabromodiosmate(III) dianion. The brown color of the salt suggests that the anion adopts an eclipsed conformation (D_4h symmetry) and this conclusion has been confirmed by a single-crystal X-ray diffraction experiment. The X-ray crystal structure indicates that the osmium atoms in the anion are disordered over two sites. The bromine atoms show no evidence of disorder and are disposed in a quasi-cubic arrangement; the two Os-Os vectors are almost exactly orthogonal to each other and each vector points toward a different pair of opposite square faces of the Br₈ cube. The Os-Os bond distances are 2.219(5) and 2.229(1) Å; the average Os-Br distance in the anion is 2.417(2) Å. Treatment of [(C₅Me₄H)₂OsBr]₂[Os₂Br₈] with excess 1,5-cyclooctadiene in ethanol at gentle reflux for 3 h affords [(C₅Me₄H)₂OsBr][Os₂HBr₄(cod)₂], 2. An X-ray crystallographic study was carried out on a sample in which the cation was a mixture of [(C₅Me₄H)₂OsBr⁺] and [(C₅Me₄H)₂OsH⁺]. The results demonstrate that the anion adopts a confacial bioctahedral structure in which the hydride ligand and two bromides bridge between the two osmium centers. The CC bonds of the cod ligands are trans to the bridging bromide groups. The Os-Os bond distance in the anion is 2.874(1) Å. The average Os-Br distance is 2.596(2) Å for the bridging bromides and 2.565(2) Å for the terminal bromides. Compound 2 is the first example of an anionic diosmium complex containing a bridging hydride. The reaction of 1 with cod also results in the formation of bis(tetramethylcyclopentadienyl)osmocene, (C₅Me₄H)₂Os, 3, which has been isolated and characterized. Treatment of (C₅Me₄H)₂Os with 1.0 equiv. of HBF₄ · Et₂O affords the osmocinium salt [(C₅Me₄H)₂OsH][BF₄].     

X-ray crystal structures and solution dynamics of sodium organofluorotitanates [Na{Ti2(C5Me5)2F7}] and [NaTi6(C5Me5)5F20(H2O)]·(THF)

[Na{Ti₂(C₅Me₅)₂F₇}] (1) was prepared from sodium fluoride and [{Ti(C₅Me₅)F₃}₂] [H.W. Roesky, et al., Angew. Chem. Int. Ed. Engl. 31 (1992) 864-866]. The solid-state 1 consists of a polymeric chain of two rows of dititanate anions [Ti₂(C₅Me₅)₂F₇]⁻ connected by sodium ions in the middle of the chain. Each sodium ion is coordinated by five fluorine atoms from three [Ti₂(C₅Me₅)₂F₇]⁻ anions. The variable-temperature ¹⁹F NMR of CD₃CN solution of 1 revealed interconversions of monomeric species [Na(CD₃CN)_n{Ti₂(C₅Me₅)₂F₇}] (1solv) with different number of CD₃CN ligands on the sodium ion. The addition of HMPA to the CD₃CN solution of 1 allows ¹⁹F NMR observation of 1·HMPA (1a) and 1·HMPA·CD₃CN (1b) in the slow exchange. The solid-state structure of [NaTi₆(C₅Me₅)₅F₂₀(H₂O)]·(THF) (2·THF) reveals the sodium ion coordinated by four fluorine atoms from the anion [Ti₂(C₅Me₅)₂F₇]⁻ and by three fluorine atoms from the cluster [Ti₄(C₅Me₅)₃F₁₃(H₂O)].     

Synthesis, structural characterization and reactivity of new tin bridged ansa-bis(cyclopentadiene) compounds: X-ray crystal structures of Me2Sn(C5Me4R-1)2 (R = H, SiMe3)

The organo-tin compounds, Me₂Sn(C₅H₄R-1)₂ (R = Me (1), Prⁱ (2), Bu^t (3), SiMe₃ (4)) and Me₂Sn(C₅Me₄R-1)₂ (R = H (5), SiMe₃ (6)), were prepared by the reaction of Me₂SnCl₂ with the lithium or sodium derivative of the corresponding cyclopentadiene. Compounds 1-6 have been characterized by multinuclear NMR spectroscopy (¹H, ¹³C, ¹¹⁹Sn). In addition the molecular structures of 5 and 6 were determined by single crystal X-ray diffraction studies. The transmetalation reaction of 1-6 with ZrCl₄ or [NbCl₄(THF)₂] gave the corresponding metallocene complexes in high yields.     

Lutetium gets a crown: Synthesis, structure and reaction chemistry of the separated ion pair complex, [Li(12-crown-4)2][(C5Me5)2LuMe2]

Reaction of (C₅Me₅)₂Lu(Me)(μ-Me)Li(THF)₃ (2) with excess 12-crown-4 affords the new separated ion pair complex, [Li(12-crown-4)₂][(C₅Me₅)₂LuMe₂] (3), in excellent yield. This complex reacts with 2,6-diisopropylaniline and phenylacetylene to give the methyl amide complex [Li(12-crown-4)₂][(C₅Me₅)₂Lu(Me)(NH-2,6-ⁱPr₂C₆H₃)] (4) and the bis(acetylide) complex [Li(12-crown-4)₂][(C₅Me₅)₂Lu(C≡C-Ph)₂] (5), respectively. Attempts to promote methane loss from complexes 3 and 4 to generate a lutetium methylidene or imido complex, respectively, were unsuccessful. The ability of the bis(acetylide) complex 5 to act as a π-tweezer complex was also explored. Reaction between [Li(12-crown-4)₂][(C₅Me₅)₂Lu(C≡C-Ph)₂] (5) and CuSPh gave only intractable lutetium products and the copper(I) species [Li(12-crown-4)₂][Cu(C≡C-Ph)₂] (8). The new lutetium complexes have been characterized by elemental analysis and NMR spectroscopy. Finally, the X-ray crystal structures of (C₅Me₅)₂Lu(Me)(μ-Me)Li(THF)₃ (2), [Li(12-crown-4)₂][(C₅Me₅)₂LuMe₂] (3), [Li(12-crown-4)₂][(C₅Me₅)₂Lu(Me)(NH-2,6-ⁱPr₂C₆H₃)] (4), [Li(12-crown-4)₂][(C₅Me₅)₂Lu(C≡C-Ph)₂] (5), and [Li(12-crown-4)₂][Cu(C≡C-Ph)₂] (8) are also reported.     

Olefin uptake as tool for linking platinum(II) and iridium(III) in heterobinuclear complexes: Synthesis and characterization of [PtI2(Me2phen){(C5Me4CH2CH2CHCH2)Ir(Me)(CO)(Ph)}]

The ability of [PtX₂(Me₂phen)] (Me₂phen = 2,9-dimethyl-1,10-phenanthroline, X = Cl, Br, I) to act as olefin scavengers, easily giving stable trigonal bipyramidal five-coordinated platinum species [PtX₂(Me₂phen)(η²-olefin)], has been checked toward [(C₅Me₄CH₂CH₂CHCH₂)Ir(Me)(CO)(Ph)], a cyclopentadienyl complex containing an olefinic function introduced by ring methyl activation in the pentamethylcyclopentadienyl iridium(III) complex [(C₅Me₅)Ir(Me)(CO)(Ph)]. The reaction of [PtI₂(Me₂phen)] with [(C₅Me₄CH₂CH₂CHCH₂)Ir(Me)(CO)(Ph)] results in the formation of the heterometallic binuclear complex [PtI₂(Me₂phen){(C₅Me₄CH₂CH₂CHCH₂)Ir(Me)(CO)(Ph)}] which is stable and has been completely characterized by elemental analysis, ¹H, ¹³C, and ¹⁹⁵Pt NMR spectroscopy.     

Dreikern- sowie homo- und heterometall-zweikernkomplexe mit der baueinheit C5Me5Rh. Die kristallstruktur von C5Me5[P(OMe)3[Rh(μ-CO)2RhC5Me5

C₅Me₅Rh(L)P₂Me₄ (L = CO, C₂H₄) reacts with [C₅Me₅Rh(μ-CO)]₂, to give the trinuclear complexes C₅Me₅(L)Rh(μ-P₂Me₄)RhC₅Me₅(μ-CO)₂RhC₅Me₅ (VI, VII). In the reactions of C₅Me₅Rh(CO)P₂Me₄ with C₅H₅(CO)₂ (M = Rh, Co) and C₅H₄RMn(CO)₃ (R = H, Me), the homo- and hetero-metallic binuclear compounds C₅Me₅(CO)Rh(μ-P₂Me₄)M(CO)C₅H₅ (VIII, IX) and C₅Me₅(CO)Rh(μ-P₂Me₄)Mn(CO)₂C₅H₄R (X, XI) are obtained in almost quantitative yield. The X-ray structure of the complex C₅Me₅[P(OMe)₃]Rh(μ-CO)₂RhC₅Me₅ (III), which is structurally related to VI and VII, has been determined. The molecule contains an unsymmetrical, non-planar Rh₂C₂-skeleton with different Rh-C(O) bond lengths. The Rh-Rh distance is 268.5(1) pm; the planes of the two five-membered rings form an angle of 62.6°.     

Unsymmetrische(Rh—Rh)-zweikernkomplexe mit 34 valenzelektronen: Synthese und eigenschaften von C5Me5(L)Rh(μ-CO)2RhC5Me5

[C₅Me₅Rh(μ-co)]₂ reacts with phosphines (PMe₂H, PMe₃) and trimethylphosphite to give the binuclear complexes C₅Me₅(L)Rh(μ-CO)₂RhC₅Me₅ which have been characterised by elemental analyses, mass spectra,¹H and ³¹P NMR data. They are surprisingly inert toward an excess of L and do not react to give the mononuclear compounds C₅Me₅Rh(CO)L. These are obtained in good yields from C₅Me₅Rh(CO)₂ and L where L is PMe₂H, P(OMe)₃, PEt₃, P(OEt)₃ and PMe₂Ph.     

Complex formation between water-soluble sulfonated calixarenes and C60 fullerene

The inclusion complexes of sulfonated thiacalix[4]arene 1 and calix[6]arene 2 sodium salts with C₆₀ fullerene were investigated by photoluminescence (PL) and quantum-chemical methods. The stoichiometries of calixarene/C₆₀ complexes were found to be 2:1 for 1 and 1:1 for 2. Related quantum-chemical investigations show that C₆₀ fullerene is included in a cavity composed of two half-bowl molecules of 1. The C₆₀ fullerene ball is located deep within the cavity of 2 and the negatively charged sulfonate arms probably inhibit the formation of the bowl-shaped capsule that was observed in the case of 1.     

Synthese und eigenschaften neur kupfer- und gold-komplexe des typs C5H5MPR3, C5Me5MPR3 und R″C2MPR3 (M = Cu,Au) sowie die kristallstruktur von C5H5AuPPr3i

The complexes C₅H₅CuPR₃ (R = Me, Prⁱ), C₅H₅AuPR₃ (R = Me, Prⁱ), C₅Me₅CuPR₃ (R = Me, Prⁱ, Ph) and C₅Me₅AuPR₃ (R = Prⁱ, Ph) are prepared from [ClCuPR₃]_n or ClAuPR₃ and LiC₅H₅ (TlC₅H₅) or LiC₅Me₅, respectively. According to the ¹H and ¹³C NMR spectra, the cyclopentadienyl and pentamethylcyclopentadienylgold compounds are fluxional in solution. The X-ray crystal structure of C₅H₅AuPPr₃ⁱ has been determined at ?120°C. The gold atom is in a linear arrangement (PAuC(1) = 177.0(2)°) and primarily σ-bonded to the cyclopentadienyl ring which shows a weak “slip distortion” toward a η³-mode of coordination. The complexes C₅R′₅AuPR₃ (R′ = H, Me) and C₅Me₅CuPPr₃ⁱ react with 1-alkynes such as C₂H₂, HC₂Ph and HC₂CO₂Me to form alkinylgold and copper compounds R″C₂MPR₃. They have been characterized by IR, UV and NMR (¹H, ¹³C, ³¹P) spectroscopy.     

Complexes of titanium and zirconium based on [C5Me4CH2-(2-C5H4N)] ligand

Half-sandwich [η⁵:η¹-κN-C₅Me₄CH₂-(2-C₅H₄N)]MCl₃ (M = Ti (4), Zr (5)) and sandwich [η⁵-C₅Me₄CH₂-(2-C₅H₄N)][η⁵-C₅Me₅]ZrCl₂ (6) ring-peralkylated complexes have been prepared and characterized. Evidence of the intramolecular coordination of the side-chain pyridyl group both in 4 and 5 in solutions is provided by NMR spectroscopy data. Crystal structure of an adduct 5-py with one molecule of pyridine has been established by X-ray diffraction analysis.     

Isolation and characterisation of both the first fluoroxyfluorofullerene C60F17OF and oxahomofluorofullerenol C60F17O.OH

The first fluoroxyfluorofullerene C₆₀F₁₇OF (A) has been isolated from the fluorination of [60]fullerene with a mixture of MnF₃ and K₂NiF₆ at 480 °C. This compound has a shorter HPLC retention time than the isomeric fluorofullerene ethers (oxahomofullerenes) and is less stable towards EI mass spectrometry. It fragments by losing OF as a single entity and shows no formation of C₆₀O as a fragment ion. By contrast, the ethers fragment by first losing a number of F atoms and then CO, and ultimately show also the presence of C₆₀O, whilst epoxides lose CO as a main fragmentation step and do not give C₆₀O. The first oxahomofluorofullerenol C₆₀F₁₇O.OH (B) has been isolated from the UV-irradiation of a toluene solution of C₆₀F₁₈ in air during 65 h and readily eliminates HF due to adjacent F and OH groups during EI mass spectrometry. The structures of both the compounds have been deduced from 1D and 2D NMR spectroscopy. Just as oxygen inserts into FCCF bonds of C₆₀F₁₈ to give ethers, so insertion into a CF bond gives A. The oxahomofluorofullerenol B is produced by S_N2′ substitution of F by OH, followed by oxygen insertion into a 6:5-bond (αβ to the OH group) giving a motif not seen previously in fluorofullerenes.     

Novel sandwich complexes of zirconium [C9H5(SiMe3)2](C5Me4R)ZrCl2 (R = CH3, CH2CH2NMe2): Synthesis and reduction behavior

Novel half-sandwich [C₉H₅(SiMe₃)₂]ZrCl₃ (3) and sandwich [C₉H₅(SiMe₃)₂](C₅Me₄R)ZrCl₂ (R = CH₃ (1), CH₂CH₂NMe₂ (2)) complexes were prepared and characterized. The reduction of 2 by Mg in THF lead to (η⁵-C₉H₅(SiMe₃)₂)[η⁵:η²(C,N)-C₅Me₄CH₂CH₂N(Me)CH₂]ZrH (7). The structure of 7 was proved by NMR spectroscopy data. Hydrolysis of 2 resulted in the binuclear complex ([C₅Me₄CH₂CH₂NMe₂]ZrCl₂)₂O (6). The crystal structures of 1 and 6 were established by X-ray diffraction analysis.     

Crystal and molecular structure of [{Rh(C5Me5)}3Cl5np3]PF6 · 0.5 C3H8O

The crystal and molecular structure of the monoligand trimetallic complex [{Rh(C₅Me₅)}₃Cl₅np₃]PF₆ · 0.5 C₃H₈O (np₃  tris(2-diphenylphosphinoethyl)-amine) have been established by a single-crystal X-ray diffraction study. The cation of the complex contains two Rh(C₅Me₅)Cl₂ units each bound through the metal to one phosphorus atom of the ligand and a Rh(C₅Me₅)Cl group in which the rhodium is bound to the third phosphorus atom and to the nitrogen of the tetradentate ligand.The crystals are triclinic, space group P$\text{1}$, with cell dimensions a 28.598(8), b 13.757(4), c 10.748(3) Å, α 90.69(4), β 96.67(4), γ 99.71(4)°, D_c 1.38 g cm^?3 for Z  2. The structure was solved by three dimensional Patterson and Fourier syntheses and refined by least-squares techniques to a final conventional R value of 0.098.     

Reactions of benzopinacol with group 13 alkyl metals:: Crystal structure of Me6In4[OC(C6H5)2C(C6H5)2O]2(OCH3)2, a new alkylalkoxo indium diolate

Reactions of Me₅Al₃[OC(C₆H₅)₂C(C₆H₅)₂O]₂ (1) with alcohols ROH (R = Me, Et, ^tBu) in a 1:1 molar ratio afforded the compound Me₂Al₂[OC(C₆H₅)₂C(C₆H₅)₂O]₂(C₄H₈O) (2) and a mixture of methylaluminum alkoxides. The alcohols acted as the factor formally eliminating a molecule of Me₃Al (as a methylaluminum alkoxide) from compound 1. ^tBu₃Al reacted with an equimolar amount of benzopinacol to form the monomeric complex ^tBuAl[OC(C₆H₅)₂C(C₆H₅)₂O](C₄H₈O) (3). Reactions of Me₃Ga and Me₃In with benzopinacol yielded trinuclear complexes Me₅M₃[OC(C₆H₅)₂C(C₆H₅)₂O]₂ (4 (M = Ga), 5 (M = In)), isostructural to compound 1. In the presence of water and alcohols, compounds 4 and 5 underwent a decomposition reaction to benzopinacol and a mixture of metalloxanes and alkoxides. An unusual methylmethoxo indium benzopinacolate Me₆In₄[OC(C₆H₅)₂C(C₆H₅)₂O]₂(OCH₃)₂ (6) was obtained in the reaction of benzopinacol with Me₃In and Me₂InOMe in a 1:1:1 molar ratio. Molecular structures of the compounds 3, 4 and 6 were determined by X-ray crystallography.     

The ESR spectrum of the C5F5 radical

Experimental results of an investigation of the ESR spectrum of the pentafluorocyclopentadienyl radical C₅F₅ in various liquid and solid matrices are reported. At temperatures above 120 K the ESR spectra indicate a five-fold symmetry with a fluorine isotropic splitting of 16 G and an isotropic g tensor of 2.0041. From liquid solutions a value A_iso¹³C ≈ 2.1 G for the isotropic coupling of the ¹³C₁ species in natural abundance was found. The ESR spectra exhibit a pronounced temperature dependence, which is interpreted by lineshape analysis to originate from an anisotropic hyperfine interaction tensor of fluoroine, partially averaged by a uniaxial rotational reorientation. From ESR spectra of polycrystalline samples the principal value A6 = 57.5–58.3 G depending on the matrix was derived.     

Selective reduction of fullerene C60 by metals in neutral and alkaline media. Interaction of C60 with KOH

The reduction of fullerene C₆₀ by Zn and Mg in DMF was studied both in the presence and absence of KOH. Fullerene C₆₀ was reduced in these systems to form the C₆₀ ^n– (n = 1, 2, and 3) anions. The anions were detected by optical and ESR spectroscopies. It was found that Mg reduced C₆₀ to the monoanion, Mg/KOH and Zn reduced C₆₀ to the dianion, and Zn/KOH reduced C₆₀ to the trianion. Like KCN, potassium hydroxide adds to fullerene upon interaction with C₆₀ in DMF. The reaction of C₆₀ with KOH in benzonitrile was accompanied by the generation of the fullerene monoanion. A possible mechanism of the formation of fullerene monoanions in the presence of KOH is discussed. The degradation of the C₆₀ ^n– anions in air was studied.     

Crystal structures of [Rh(η-C5H5)(C3S5)] and [Rh(η-C5Me5)(C3S5)]2 and properties of their oxidized species

[Rh(η⁵-C₅H₅)(C₃S₅)] and [Rh(η⁵-C₅Me₅)(C₃S₅)]₂ [C₃S₅²⁻=4,5-disulfanyl-1,3-dithiole-2-thionate(2-)] were prepared by reactions of [NMe₄]₂[C₃S₅] with [Rh(η⁵-C₅H₅)Cl₂]₂ and [Rh(η⁵-C₅Me₅)Cl₂]₂, respectively. Their X-ray crystal structural analyses revealed a monomeric form for the former complex and a dimeric geometry containing bridging S-Rh-S bonds for the latter in the solid state. They were reacted with bromine to afford [RhBr(L)(C₃S₅)] (L=η⁵-C₅H₅ and η⁵-C₅Me₅) with the Rh-Br bond and one electron-oxidation on the C₃S₅ ligand. ESR spectra and spin densities for these oxidized species are discussed.     

Stability of functionalized C60 paramagnetic dimers and monomers

Density functional theory is used to calculate the bond dissociation energy to cleave the C₆₀C₆₀ bond of the paramagnetic X-C₆₀C₆₀-X and X-C₆₀C₆₀ dimers where X is F, OH, O and H. The results show that these dimers would not be stable much above room temperature and therefore cannot constitute the paramagnetic phase needed to form the observed ferromagnetism which has been shown to be stable up to 800 K. The calculated bond dissociation energies to remove an F, OH or H from a single C₆₀ are large suggesting that they could be the source of the unpaired spin needed for the high temperature ferromagnetism.     

Radical scavenging efficiency of different fullerenes C60-C70 and fullerene soot

This investigation was undertaken to determine the antioxidant activity of a range of fullerenes C₆₀ and C₇₀ in order to rank them according to their comparative efficiency. The model reaction of initiated (2,2′- azobisisobutyronitrile, AIBN) cumene oxidation was used to determine rate constants for addition of radicals to fullerenes. Measurements of oxidation rates in the presence of different fullerenes showed that the antioxidant activity as well as the mechanism and mode of inhibition were different for fullerenes C₆₀ and C₇₀ and fullerene soot. All fullerenes - C₆₀ of gold grade, C₆₀/C₇₀ (93/7, mix 1), C₆₀/C₇₀ (80 ± 5/20 ± 5, mix 2) and C₇₀ operated as alkyl radical acceptora, whereas fullerene soot surprisingly retarded the model reaction by a dual mode similar to that for the fullerenes and with an induction period like many of the sterically hindered phenolic and amine antioxidants. For the C₆₀ and C₇₀ the oxidation rates were found to depend linearly on the reciprocal square root of the concentration over a sufficiently wide range thereby fitting the mechanism for the addition of cumylalkyl radicals to the fullerene core. This is consistent with literature data on the more ready and rapid addition of alkyl and alkoxy radicals to the fullerenes compared with peroxy radicals. Rate constants for the addition of cumyl radicals to the fullerenes were determined to be k_(333K) = (1.9 ± 0.2) × 10⁸ (C₆₀); (2.3 ± 0.2) × 10⁸ (C₆₀/C₇₀, mix 1); (2.7 ± 0.2) × 10⁸ (C₆₀/C₇₀, mix 2); (3.0 ± 0.3) × 10⁸ (C₇₀), M⁻¹ s⁻¹. The increasing C₇₀ constituent in the fullerenes leads to a corresponding increase in the rate constant.The fullerene soot inhibits the model reaction according to the mechanism of trapping of peroxy radicals; the oxidation proceeds with a pronounced induction period and kinetic curves are linear in semi-logarithmic coordinates.For the first time the effective concentration of inhibiting centres and inhibition rate constants for the fullerene soot have been determined to be fn[C₆₀−soot] = (2.0 ± 0.1) × 10⁻⁴ mol g⁻¹ and k_inh = (6.5 ± 1.5) × 10³ M⁻¹ s⁻¹ respectively.The kinetic data obtained specify the level of antioxidant activity for the commercial fullerenes and scope for their rational use in different composites. The results may be helpful for designing an optimal profile of composites containing fullerenes.