On the possibility of existence of η5-π-complexes of C60 fullerene: π-complexes with silicon

Qualitative estimates of possibility of the formation of fullerene ⁵--complexes have been carried out by the MNDO/PM3 method. It was shown, as exemplified by the C₆₀ cluster, that the introduction of five univalent functional groups R (R = H, Cl, Br) to -positions of a separate pentagon of C₆₀ with the formation of [R₅C₆₀]^– anions results in a pronounced increase in the -electron density on the atoms of this five-membered cycle and more favorable conditions for the formation of -bonds with the ⁵-ligand. The nature of the interaction between the atoms of the separate cycle in [R₅C₆₀]^– anion and ⁵-ligand was analyzed by the example of hypothetical sandwich systems R₅C₆₀SiCp. Half-sandwich complexes R₅C₆₀SiX (X = H, Cl) were also investigated. The local energy minima were found on the potential energy surfaces (PES) of systems R₅C₆₀SiCp and R₅C₆₀SiX with C_5p symmetry. These systems transform barrirlessly into q5-7E-complexes with the angular structure if the symmetry restrictions are removed. The most favorable conditions for ⁵--complexes of R₅C₆₀ to form are realized for R = H. The results obtained were compared to those of semiempirical and nonempirical calculations of bis (cyclopentadienyl) silicon.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2422–2429, October, 1996.     

Exohedral η5-π-complexes of fullerene C20

The problem of stabilization of polyhedral carbon clusters, which do not obey the isolated pentagon rule, is discussed taking a dodecahedral fullerene C₂₀ as an example. Ab initio MO LCAO calculations in the HF/3-21G approximation showed that fullerene C₂₀ as well as its C₂₀H₅ hydrides with C _5v symmetry can form stable 2⁵--complexes of the CpFeC₂₀FeCp and H₅C₂₀FeC₂₀H₅ types. The energies of the ⁵-Fe--C₂₀ -bonds in these complexes were compared with those of the Fe--Cp bond in ferrocene and the Fe--C₆₀ bond in the ⁵--C₆₀H₅FeCp complex.     

Structure and properties of ionic fullerene complex Co(+)(dppe)2·(C60˙-)·(C6H4Cl2)2: distortion of the ordered fullerene cage of C60˙- radical anions

New ionic complex {Co(+)(dppe)(2)}·(C(60)˙(-))·(C(6)H(4)Cl(2))(2) (1) was obtained by the reduction of a Co(dppe)Br(2) and C(60) mixture by TDAE in o-dichlorobenzene followed by precipitation of crystals by hexane. Optical and EPR spectra of 1 indicated the formation of C(60)˙(-) radical anions and diamagnetic Co(+)(dppe)(2) cations. The structure of 1 solved at 100(2) K involves chains of C(60)˙(-) arranged along the lattice a-axis with a center-to-center distance of 10.271 ?. The chains are separated by bulky Co(+)(dppe)(2) cations and solvent molecules. All components of 1 are well ordered allowing the distortion of the C(60)˙(-) radical anion to be analyzed. An elongation of the C(60)˙(-) sphere by 0.0254(2) was found. It is essentially smaller than those in the salts (Cp*(2)Ni(+))·(C(60)˙(-))·CS(2) and (PPN(+))(2)·(C(60)(2-)) with greater distortion of the fullerene cage. The calculation of the electronic structure of fullerene by the extended Hückel method showed slight splitting of the C(60) LUMO, due to the distortion, by three levels. Two levels are located 180 and 710 cm(-1) higher than the ground level. The averaged 6-6 and 5-6 bonds in C(60)˙(-) with lengths of 1.397(2) and 1.449(2) ? are close to those determined for the C(60)(2-) dianions in (PPN(+))(2)·(C(60)(2-)), but are slightly longer and shorter, respectively, than the length of these bonds in neutral C(60).     

Synthesis and characterization of adducts of p-azidostyrene derivatives to fullerene C_(60)

Fullerene C60 reacted with p-azidostyrene derivatives in refluxing chlorobenzene,yielding monoadducts 2a and 2d as well as diadduct 2c with aziridine structure at 6/6-ring junctions.Experimental results showed that the addition of the second azide to the monoadduct was regioselective.The diadduct,of Cs symmetry in C60 moiety,was unstable by opening to be 1,6-imido[10]annulene structure.     

Fullerene C60 as a η5- and η6-ligand in sandwich-type π-complexes with transition metals

The molecular and electronic structures of some hypothetical sandwich-type -complexes of transition metals with fullerene C₆₀ were modeled. The M-C₆₀ bonds in ⁵-C₆₀MCp⁺ complexes (M = Fe, Ru, Os) are less strong than the M-Cp bonds in ferrocene, ruthenocene, and osmocene, respectively. The ⁶-C₆₀MC₆H₆ complexes (M = Cr, Mo, W) should be less stable than their classical analogs (C₆H₆)M(C₆H₆). The coordination of a metal atom with the fullerene at its pentagonal face is more energetically favorable than at a hexagonal face.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 598–601, April, 1994.We are grateful to V. I. Sokolov for discussion of the results obtained. This study was supported by the Russian Foundation for Basic Research (grants 93-03-4101 and 93-03-18725).     

Efficient synthesis of 1-alkyl-3-methylimidazolium fluorides and possibility of the existence of hydrogen bonding between fluoride anion and C(sp3)–H

1-Alkyl-3-methylimidazolium fluorides were successfully synthesized by the reaction of silver fluoride with the corresponding imidazolium iodides.     

Cupro(I)-π-complexes with 1-allyloxybenzotriazole: Synthesis and crystal structure of CuBF4 · 2C6H4N3(OC3H5) · H2O and CuCF3COO · C6H4N3(OC3H5)

The crystals of copper(I) π-complexes CuBF₄ · 2C₆H₄N₃(OC₃H₅) · H₂O (I) and CuCF₃COO · C₆H₄N₃(OC₃H₅) (II) were obtained by alternating-current electrosynthesis and studied by X-ray diffraction: I, space group P2₁/n, a = 10.226(8), b = 13.233(10), c = 16.30(1) Å, β = 98.13(1)°, V = 2249(2) ų, Z = 4, R = 0.0705, 577 reflections; I, space group P $ P\bar 1 The crystals of copper(I) π-complexes CuBF₄ · 2C₆H₄N₃(OC₃H₅) · H₂O (I) and CuCF₃COO · C₆H₄N₃(OC₃H₅) (II) were obtained by alternating-current electrosynthesis and studied by X-ray diffraction: I, space group P2₁/n, a = 10.226(8), b = 13.233(10), c = 16.30(1) ?, β = 98.13(1)°, V = 2249(2) ?³, Z = 4, R = 0.0705, 577 reflections; I, space group P , a = 8.8625(7), b = 9.0647(4), c = 9.1650(5) ?, α = 68.37(2)°, β = 85.31(3)°, γ = 69.86(2)°, V = 646(4) ?³, Z = 2, R = 0.1354, 2669 reflections. In compound I, the tetrahedrally distorted trigonal pyramidal environment of the copper atom comprises two nitrogen atoms of two organic molecules (L), the C=C bond of another L molecule, and the O atom of the water molecule. Due to the bridging function of L molecule, infinite chains [Cu · 2C₆H₄N₃(OC₃H₅) · H₂O] _n are formed in the structure along the y axis. The chains are, in turn, assembled into layers through strong O-H…F hydrogen bonds involving both hydrogen atoms of the water molecule and fluorine atoms of the BF₄⁻ anion. In compound II, two bridging oxygen atoms of two trifluoroacetate anions and two copper atoms form a centrosymmetric dimer. The nitrogen atom of the benzotriazole ring of one molecule L and the C=C double bond of the allyl group of the other molecule L complete the distorted coordination tetrahedron of the metal atom. Owing to the bridging function of the L molecule, the [CuCF₃COO · C₆H₄N₃(OC₃H₅)]₂ dimers are connected to form infinite double chains associated in a three-dimensional framework by only weak interactions. The replacement of the covalently bonded trifluoroacetate anion by an outer-sphere tetrafluoroborate ion opens up the possibility for metal atom binding to three L molecules simultaneously. Original Russian Text ? E.A. Goreshnik, M.G. Mys’kiv, 2008, published in Koordinatsionnaya Khimiya, 2008, Vol. 34, No. 11, pp. 826–830.     

The reaction of diaryl derivatives of bis(triphenylphosphine)platinum(II) with [60]fullerene as a route to the platinum complex η2-C60Pt(PPh3)2

The reaction ofcis-Ar₂Pt(PPh₃)₂ (Ar=p-MeC₆H₄ (1a) and Ar=Ph (1b)) with [60]fullerene in toluene afforded the metal-fullerene complex η²-C₆₀Pt(PPh₃)₂ (2), which was isolated in the crystalline state. The reductive elimination between C₆₀ and1a or1b also resulted in the formation of biaryls (p-MeC₆H₄)₂ and Ph−Ph. The composition and structure of the compounds were established by¹H and³¹P NMR spectroscopy, electronic absorption spectroscopy, and elemental analysis. The homolytic phosphorylation of2 was additionally studied by the ESR method.     

Study of η5-(1-chloro-4-methylcyclohexadienyl) and η5-(1-methyl-4-chlorocyclohexadienyl)tricarbonylmanganese complexes in solution and in the solid state

The spectroscopic studies of neutral η⁵-(1-chloro-4-methylcyclohexadienyl) and η⁵-(1-methyl-4-chlorocyclohexadienyl) tricarbonylmanganese complexes have been realized in solution by ¹H NMR spectroscopy as well as in the solid state. The structures showed a dihedral angle of the sp³ carbon of 33.2° and 36.6° with respect to the cyclohexadienyl ring. To cite this article: F. Rose-Munch et al., C. R. Chimie 6 (2003).     

Synthesis of the phosphino-fullerene PPh2(o-C6H4)(CH2NMeCH)C60 and its function as an η1-P or η3-P,C2 ligand

Following the method of Prato et al., reaction of C(60), N-methylglycine and o-(diphenylphosphino)benzaldehyde affords PPh(2)(o-C(6)H(4))(CH(2)NMeCH)C(60) (1) in moderate yield. Compound 1 reacts with W(CO)(4)(NCMe)(2) to produce W(CO)(4)(η(3)-PPh(2)(o-C(6)H(4))(CH(2)NMeCH)C(60)) (2), through coordination of the phosphine group and one 6 : 6-ring junction of fullerene. Reaction of 1 and Os(3)(CO)(11)(NCMe) affords Os(3)(CO)(11)(PPh(2)(o-C(6)H(4))(CH(2)NMeCH)C(60)) (3), which undergoes a cluster fragmentation reaction in refluxing toluene to produce Os(CO)(3)(η(3)-PPh(2)(o-C(6)H(4))(CH(2)NMeCH)C(60)) (4). Thermal reaction of 1 and Os(3)(CO)(12) affords 3 and 4. On the other hand, reaction of 1 and Ru(3)(CO)(12) yields only the mononuclear complex Ru(CO)(3)(η(3)-PPh(2)(o-C(6)H(4))(CH(2)NMeCH)C(60)) (5). The structures of 1-3 and 5 were determined by an X-ray diffraction study.     

Synthesis,characterization and kinetic computations of fullerene (C60)–CuO on the mechanism decomposition of ammonium perchlorate

CuO, C₆₀–CuO, and Al/C₆₀–CuO nanostructures were synthesized and characterized by scanning electron microscope (SEM)/energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR). differential scanning calorimetry (DSC)/thermogravimetric analysis (TGA) measurements were performed to study the influence of these additives on ammonium percolate (AP) thermal decomposition. From the comparison of DSC and TGA plots, the catalytic effect of CuO and C₆₀–CuO has been clearly noticed in which the lower temperature decomposition of AP was decreased from 331 °C to 315 °C, 310 °C, and 303 °C (in the presence of CuO, C₆₀–CuO, and Al/C₆₀–CuO, respectively) and the HTD was dropped from 430 °C (pure AP) to 352 °C, 335 °C, and 317 °C (for the compounds AP/CuO, AP/C₆₀–CuO, and AP/Al/C₆₀–CuO, respectively). The kinetics of the samples were investigated by isoconversional models and compared with an iterative procedure. The results of pure AP indicated a complex decomposition process involving three decomposition steps with specific reaction mechanism. The nanocatalysts incorporated in the AP have clearly affected its decomposition process in which the reaction mechanism and the number of stages were changed.     

π-π interactions in the self-assembly of melamine and barbituric acid derivatives

Self-assembly of a pair of complementary molecular components, 5-(4-dodecyloxyben-zylidene)-(1H,3H)-2, 4,6-pyrimidinetrione (PB₁₂)and 4-amino-2,6-didodecylamino-1, 3, 5-triazine (M₁₂) was studied by cyclic voltammogram, surface photovoltage spectroscopy, fluorescence spectroscopy, FTIR and X-ray diffraction. It is found that after mixing equimolar amount of PB₁₂ and M₁₂ at room temperature, not only triply complementary hydrogen bonds are formed between PB₁₂and M₁₂ but also further self-assembly of the supermolecules based on network of hydrogen bonds occurs via π-π interactions. During the self-assembly of the supermolecules, π -π interactions are induced by delocalized interactions between the HOMO of M₁₂ and the LUMO of PB₁₂, resulting in the formation of a supramolecular nanotube with a layered structure bearing a d value of 0.41 nm and PB₁₂ and M₁₂are arranged alternatively between adjacent supermolecules.     

Theoretical study of C60(OH)20 and C60(OH)18 fullerenols and B12(OH) 12 2? , Si20O30(OH)20, and Ti20O30(OH)20 polyhydroxyl clusters and their Li-substituted derivatives

The equilibrium geometric parameters and the energetic characteristics of fullerenol molecules C₆₀(OH)₂₀ and C₆₀(OH)₁₈ and fullerenol-like inorganic clusters B₁₂(OH) ₁₂ ^2? , Si₂₀O₃₀(OH)₂₀, and Ti₂₀O₃₀(OH)₂₀ and their derivatives C₆₀(OH)_{20 ? n} (OLi) _n , C₆₀(OH)_{18 ? n} (OLi) _n , B₁₂(OH)_{12 ? n} (OLi) _n ^2? , Si₂₀O₃₀(OH)_{20 ? n} (OLi) _n , and Ti₂₀O₃₀(OH)_{20 ? n} (OLi) _n , in which the H atoms of all or one-half of hydroxyl groups are replaced by Li atoms, have been calculated by the density functional theory B3LYP/6-31G* method. It has been found that partial energies ??E(H/Li) per single substitution of Li for H in the reactions C₆₀(OH)₂₀ + nLiAc ?? C₆₀(OH)_{20 ? n} (OLi) _n + nHAc and C₆₀(OH)₁₈ + nLiAc ?? C₆₀(OH)_{18 ? n} (OLi) _n + nHAc (Ac is acetate) and the energies averaged over the entire series of changes in n, as well as over its first and second halves, do not exceed a few kilocalories per mole. It has been predicted that at least one-half (or more than one-half) of OH groups can be replaced by OLi without noticeable changes in energy; however, with a further increase in n, substitutions become endothermic and require ever-increasing energy inputs. In the completely hydroxylated closo-dodecaborane dianion with an icosahedral [B₁₂] cage and more polar B-O-H bonds, analogous H/Li substitutions are slightly exothermic so that the reaction can proceed somewhat smoother and further (toward larger n values) than in fullerenols, other conditions being the same. In the inorganic clusters Si₂₀O₃₀(OH)₂₀ and Ti₂₀O₃₀(OH)₂₀ with the [Si₂₀] and [Ti₂₀] cages, respectively, and with even more polar Si-O-H and Ti-O-H moieties, the substitutions are even more exothermic (their partial energies ??E(H/Li) increase to 4?C6 kcal/mol). For sodium and potassium analogues, the qualitative pattern persists, but H/Na and H/K substitutions are somewhat less exothermic than the H/Li substitutions. The results are compared to the data of previous calculations of stepwise H/Li and H/Na substitutions in the reactions C60(OH)24 + nLAc ?? C60(OH)_{24 ? n} (OL) _n + nHAc (L = Li, Na).     

Volume properties and refraction of aqueous solutions of bisadducts of light fullerene С60 and essential amino acids lysine,threonine, and oxyproline (С60(C6H13N2O2)2, С60(C4H8NO3)2, and С60(C5H9NO2)2) at 25°C

Concentration dependences of the density of aqueous solutions of bisadducts of light fullerene С₆₀ and essential amino acids are studied by pycnometry. Concentration dependences of the average molar volumes and partial volumes of components (Н₂О and corresponding bisadducts) are calculated for С₆₀(C₆H₁₃N₂O₂)₂–Н₂О, С₆₀(C₄H₈NO₃)₂–Н₂О, and С₆₀(C₅H₉NO₂)₂–Н₂О binary systems at 25°C. Concentration dependences of the indices of refraction of С₆₀(C₆H₁₃N₂O₂)₂–Н₂О, С₆₀(C₄H₈NO₃)₂–Н₂О, and С₆₀(C₅H₉NO₂)₂–Н₂О binary systems are determined at 25°C. The concentration dependences of specific refraction and molar refraction of bisadducts and aqueous solutions of them are calculated.

     

π-π interactions in the self-assembly of melamine and barbituric acid derivatives

Self-assembly of a pair of complementary molecular components, 5-(4-dodecyloxyben-zylidene)-(1H,3H)-2,4,6-pyrimidinetrione (PB12) and 4-amino-2,6-didodecylamino-1, 3, 5-triazine (M12) was studied by cyclic voltammogram, surface photovoltage spectroscopy, fluorescence spectroscopy, FTIR and X-ray diffraction. It is found that after mixing equimolar amount of PB12 and M12 at room temperature, not only triply complementary hydrogen bonds are formed between PB12 and M12 but also further self-assembly of the supermolecules based on network of hydrogen bonds occurs via π-π interactions. During the self-assembly of the supermolecules, π-π interactions are induced by delocalized interactions between the HOMO of M12 and the LUMO of PB12, resulting in the formation of a supramolecular nanotube with a layered structure bearing a d value of 0.41 nm and PB12 and M12are arranged alternatively between adjacent supermolecules.     

Preparation of η2-complexes of fullerenes by reduction. Crystal structure and optical properties of {Ni(dppp)·(η2-C70)}·(C6H4Cl2)0.5

The new reduction method for preparation of η(2)-complexes of fullerenes with nickel-1,3-bis(diphenylphosphino)propane has been developed in which Ni(dppp)Cl(2) and C(60)(C(70)) mixtures are reduced with sodium tetraphenylborate. Single crystals of the first η(2)-complex of nickel with fullerene C(70): {Ni(dppp)·(η(2)-C(70))}·(C(6)H(4)Cl(2))(0.5) (1) (C(6)H(4)Cl(2) = o-dichlorobenzene) have been obtained as well as the previously described complex with fullerene C(60): {Ni(dppp)·(η(2)-C(60))}·(Solvent) (2). The crystal structure of 1 has been solved to show the coordination of nickel to the C-C bond of C(70) at the 6-6 ring junction of η(2)-type to form Ni-C(C(70)) bonds of 1.929-1.941(2) ? length, the shortest M-C bonds among those known for η(2)-complexes of fullerenes C(60) and C(70). The length of the C-C bond to which Ni atom is coordinated (1.494(3) ?) is noticeably longer than the average length of these bonds in C(70) (1.381(2) ?). Optical spectra of 1 in the IR- and UV-visible ranges have been analyzed to show the splitting of some C(70) bands due to C(70) symmetry lowering. The complex has a red-brown color in solution and manifests three bands in the visible range at 379, 467 and 680 nm. The solution of 1 is air sensitive since air exposure restores the color and absorption bands of the starting C(70) at 383 and 474 nm.     

Simulation of the molecular and electronic structure of C60 fullerene π-complex with twelve half-sandwich species FeC5H5

The problem of existence of ⁵--complexes of fullerenes and their derivatives is discussed. The stability of the ⁵--complex C₆₀(FeCp)₁₂ (viz., icosahedral C₆₀ fullerene coated with twelve FeCp groups, each coordinated to its own pentagonal face of the fullerene cage) was first estimated in the framework of density functional approach (PBE approximation). The molecular and electronic structure of a biradical complex of C₆₀ fullerene with ten FeCp groups, C₆₀(FeCp)₁₀ (D _5d symmetry), and a 2⁵--complex of substituted fullerene H₁₀C₆₀, H₁₀C₆₀(FeCp)₂ (D _5d symmetry) in which hydrogen atoms are attached to the C atoms in the -positions relative to the atoms of the polar five-membered cycles, was simulated. According to calculations, the coated complex, I _h-C₆₀(FeCp)₁₂, should be much more stable than the complex of naked fullerene with one or two polarly located FeCp groups and only slightly less stable than the ferrocene molecule FeCp₂. The existence of C₆₀(FeCp)₁₂ and H₁₀C₆₀(FeCp)₂ complexes was suggested.     

Deoxygenation of some α-dicarbonyl compounds by tris(diethylamino)phosphine in the presence of fullerene C60

The reactions of such cyclic α-diketones as acenaphthenequinone, aceanthrenequinone, and N-alkylisatins, with hexaethyltriaminophosphine in the presence of the fullerene C(60), lead to the formation of methanofullerene derivatives under mild conditions. This process proceeds via deoxygenation of the dicarbonyl compound by the P(III) derivative and is likely to involve the intermediate formation of α-ketocarbenes. The structure of some methanofullerenes has been confirmed by NMR and XRD. The electrochemical behavior of the methanofullerenes was also investigated.