CF3 CO Research Articles

Synthesis, structure and electrochemical properties of N-substituted diiron azadithiolates as active site models of Fe-only hydrogenases

As biomimetic models for the active site of Fe-only hydrogenases,six new N-substituted diiron azadithiolates (ADT) were prepared.Treatment of CH 2Cl 2 solutions of primary amines RNH 2 with paraformaldehyde followed by an excess of SOCl 2 gave N, N-bis(chloromethyl)amines RN(CH 2Cl) 2 ( 1,R = CH 2CO 2Et; 2,C 6H 4C(O)Me- p; 3,C 6H 4CO 2Me- p; 4,C 6H 4SCN- p) in 30–90% yields.Further treatment of the chloromethylated amines 1– 4 with ( μ-LiS) 2Fe 2(CO) 6 in THF resulted in formation of the corresponding N-substituted ADT-type models [( μ-SCH 2) 2NR]Fe 2(CO) 6 ( 5,R = CH 2CO 2Et; 6,C 6H 4C(O)Me- p; 7,C 6H 4CO 2Me- p; 8,C 6H 4SCN- p) in 24–75% yields.Also prepared were the N-substituted models [( μ-SCH 2) 2NC(O)CH 2C 10H 7- α]Fe 2(CO) 6 ( 9) and 1,4-[Fe 2(CO) 6( μ- SCH 2) 2NC(O)] 2C 6H 4 ( 10) by reaction of CH 2Cl 2 solutions of [( μ-SCH 2) 2NH]Fe 2(CO) 6 with α-C 10H 7CH 2COCl and 1,4-C 6H 4(COCl) 2 in 81% and 28% yields, respectively. All the new compounds 1– 10 were characterized by elemental analysis and spectroscopy, as well as for 5– 7 and 9 by X-ray crystallography. The crystallographic studies indicated that the functionality of 5 attached to the bridged N atom lies in an equatorial position, whereas those of functionalities of 6, 7, and 9 are located in an axial position. This is presumably due to different electronic and steric effects between the N-substituted aliphatic and aromatic functionalities. More interestingly, model 7 has been found to be a catalyst for proton reduction in the presence of either strong acid CF 3CO 2H or weak acid HOAc under electrochemical conditions. In addition, two mechanisms ECCE and EECC are preliminarily suggested for such two electrocatalytic H 2 production processes, respectively.

Rectangular tetranuclear silver(I) and μ 8-selenide-centered octanuclear copper(I) complexes containing bis(diphenylphosphino)amide ligands

Interaction of Ag(CF 3CO 2) with bis(diphenylphosphino)amide (dppa) in THF gave a tetranuclear Ag 4-coplanar silver(I) complex [Ag 4(μ-dppa) 2(μ 4-O 2PPh 2) 2(μ-CF 3CO 2) 2] ( 1). The trinuclear trigonal-bipyramid copper(I) complex [Cu 3(μ 3-Cl) 2(μ-dppa) 3][CuCl 2] ( 2) was obtained from the reaction of [CuCl] powder with bis(diphenylphosphino)amide (dppa) in THF. Treatment of 2 with (Me 3Si) 2Se in THF afforded a μ 8-selenide-centered octanuclear copper(I) complex [Cu 8(μ 8-Se)(μ 4-Se)(μ 4-SeH) 3(μ-dppa) 4][(Ph 2PO) 2N] ( 3). The structures of 1– 3 were determined by single-crystal X-ray diffraction analyses. Complex 1 comprises a rectangular Ag 4 array with each edge bridged with a pair of μ-dppa, μ 4-O 2PPh 2 and μ-CF 3CO 2 ligands that are approximately perpendicular to each other. Complex 2 contains a trigonal-bipyramid [Cu 3(μ 3-Cl) 2] + core surrounded by three μ-dppa ligands. The cationic complex in 3 consists of four [Cu 2(μ-dppa)] fragments side-capped by one μ 4-Se and three μ 4-SeH ligands and center-connected by a μ 8-Se atom.

A theoretical study of thermal decomposition of CF 3CO, C 2F 5CO and C 3F 7CO

Thermal decomposition of C n F 2 n+1 CO ( n = 1–3) radicals was investigated using RRKM/ME calculations, with geometrical parameters and energetics determined at the G2M//MPW1K and CBS-QB3 levels. The decomposition rate constant of C n F 2 n+1 CO increases with increasing carbon chain length. In the atmosphere, decomposition of C 3F 7CO competes with a reaction with O 2 that produces C 3F 7C(O)O 2. The decomposition fraction of C 3F 7CO is calculated to be 73% and 50% at the G2M//MPW1K and CBS-QB3 levels under ambient conditions, whereas that of CF 3CO is 1%. The yields of C n F 2 n+1 C(O)OH, formed by the reaction of C n F 2 n+1 C(O)O 2 with HO 2, are discussed using the obtained results.

Reversible photochromism of novel silver(I) coordination complexes with 1,2-bis(2′-methyl-5′-(2″-pyridyl)-3′-thienyl)perfluorocyclopentene in crystalline phase

Three novel silver(I) complexes with 1,2-bis(2-methyl-5′-(2″-pyridyl)-3′-thienyl)perfluorocyclopentene (BM-2-PTP) were synthesized by the reaction of Ag(CF 3SO 3) or Ag(CF 3COO) with BM-2-PTP in benzene at different temperatures. The structures of these metal complexes were revealed by X-ray crystallographic analyses and the correlation between crystal structures and photochromic performance was discussed. In complexes 1 and 2, silver(I) is three-coordinated to two nitrogens from distinct ligand molecules as well as one oxygen from anions to form a 1-D polymeric structure. On the other hand, complex 3 contains two crystallographic independent Ag(I) with different coordination environments, and the adjacent BM-2-PTP molecules are connected by Ag–CF 3CO 2–Ag chains to afford a 1-D double chain structure. The difference in structures of three complexes shows the interesting anionic effect on coordination and the subtleness of crystal engineering. It is noted that complex 3 underwent reversible photochromic reaction in crystalline state despite the unfavorable framework to the rotation of thiophene groups.

Synthesis of (η 6-arene)(η 5-cyclopentadienyl) iron (II) complexes with heteroatom and carbonyl substituents. Part I: Oxygen and carbonyl substituents

A series of reactions have been used to introduce oxygen substituents into (η-arene)(η-cyclopentadienyl) iron (II) complexes. Photochemical ligand exchange led to the formation of the first recorded trioxygenated complex as well as mono- and di-oxygenated species. Using microwave techniques, reaction times for S NAr displacement reactions of halobenzene complexes by phenols were reduced from several hours to a few minutes. Phenols protected by either t-butylation or trimethylsilylation were found to give modest yields of the corresponding phenol complexes, using conventional thermal ligand exchange reactions. Without such protection, yields were extremely low. The above method led to the synthesis of the first example of a dihydroxybenzene complex. Some miscellaneous syntheses are also reported. The Nef reaction has been adapted to convert (η 6-α-nitroalkylarene)(η 5-Cp) iron (II) salts to corresponding aldehyde and ketone complexes. The α-nitroalkyl arene complexes were synthesised in good yields from (η 6-halobenzene)(η 5-Cp) iron (II) complexes using NaO tBu in DMSO. H/D exchange reactions with 2[H] 6-DMSO in the presence of K 2CO 3 showed partial D incorporation in the methyl group for the unreacted α-nitroethylbenzene complex and complete exchange for the carbanion generated by deprotonation. Conversion of the α-nitroalkylarene complexes to the corresponding aldehyde and ketone complexes was accomplished in moderate yields using three methods: (A) H 2O 2 and NaO tBu in DMSO followed by reaction with CF 3CO 2H. (B) SnCl 2/aq. HCl. (C) K 2CO 3 in DMF using microwave-mediated reactions. In addition, two one-pot syntheses are reported using methods B and C.

Peracid dependent stereoselectivity and functional group contribution to the stereocontrol of epoxidation of ( E)-alkene dipeptide isosteres

Twelve Boc-protected phenylalanyl-phenylalanine and phenylalanyl-glycine trans-vinyl isosteres were epoxidised with magnesium monoperoxyphtalate hexahydrate (MMPP) and trifluoroperacetic acid, and the results have been compared with those from earlier studies on epoxidations with m-CPBA. The alkenes were synthesised in high yields with high E/ Z-selectivities using either the Julia or Schlosser reactions. The formation of threo isomers was favoured in all epoxidation reactions except with CF 3CO 3H on substrates containing two allylic/homoallylic functional groups directing the peracid to opposite faces of the alkene. The switch to erythro selectivity observed with CF 3CO 3H is suggested to emanate from coordination to the allylic ester functionalities via hydrogen bond donation from the peracid. The other peracid reagents seem to be preferentially coordinated to the allylic carbamate function. The contribution of individual functional groups to the stereopreference was also investigated.

Silver decoration of a palladacycle through “spacer–guest” interaction

[Pd(dppf)(MeCN) 2](OTf) 2 [dppf = 1,1′-bis(diphenylphosphino)ferrocene, OTf = triflate] reacts with pyridyl acetic acid (PyAcOH) to yield a dipalladium ring structure, [Pd 2(dppf) 2(μ-PyOAc) 2](OTf) 2 ( 1). The doubly-bridging ligands exhibit basicity at the pendant carboxyl oxygen to attract AgX (X = OTf or CF 3CO 2) to form [Pd 2Ag 2(dppf) 2(PyOAc) 2(OTf) 4] ( 2) and [Pd 2Ag 2(dppf) 2(PyOAc) 2(OTf) 2(CF 3CO 2) 2] ( 3), respectively. Complexes 1 and 2 have been crystallographically characterized. Similar spacer–guest affinity is not found in the Pt(II) or isonicotinate analogues.

A Facile and Potent Synthesis of meso,meso‐Linked Porphyrin Arrays Using Iodine(III) Reagents

AbstractThe synthesis of meso,meso‐linked fluoroalkylporphyrin arrays has been accomplished, in excellent yields, by the simple treatment of a CHCl3 solution of zincated 5‐fluoroalkyl‐10,20‐diarylporphyrins (where fluoroalkyl = CF3, ClC2F4, n‐ClC4F8, n‐C6F13, etc.) with iodine(III) reagents such as PhI(O–CO–CF3)2 (PIFA, also named as bis(trifluoroacetoxy)iodo]benzene) or PhI(OAc)2 (PIDA). For nonfluorinated zincated 5‐substituted‐10–20‐diarylporphyrins (where substituent = phenyl, 4‐methoxyphenyl, 4‐methylphenyl, etc.) the similar coupling reactions also proceed fast and quantitatively. Moreover, various 15‐unsubstituted metalloporphyrins can also be coupled in high yields. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Polymerization of phenylacetylene by novel Rh (I)-, Ir (I)- and Ru (IV) 1,3-R 2-3,4,5,6-tetrahydropyrimidin-2-ylidenes (R = mesityl, 2-propyl): Influence of structure on activity and polymer structure

The preparation of novel Rh (I) and Ir (I) complexes, i.e. [Rh(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD)] +[PF 6] − ( 1), Rh(CF 3SO 3)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) ( 2) and Ir(CF 3CO 2)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) ( 3) (COD = 1,5-cyclooctadiene), is described. Compounds 1 and 3 were structurally characterized by X-ray diffraction. In 1, the N-heterocyclic carbene acts as a bidentate ligand with the carbene coordinating to the Rh(I) center and an arene group acting as a homoazallyl ligand. The catalytic activity of complexes 1– 3 in the polymerization of phenylacetylene was studied and compared to that of RhCl(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) ( 4), Rh(CF 3COO)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) ( 5), [Rh(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD)] +[BF 4] − ( 6), IrCl(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) ( 7), IrCl(1,3-diisopropyl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) ( 8), IrBr(1,3-di-2-propylimidazolin-2-ylidene)(COD) ( 9), RuCl 2(PCy 3)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)( CH–C 6H 5) ( 10), RuCl 2(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)( CH-2-(2-PrO)-5-NO 2-C 6H 3) ( 11), Ru(CO 2CF 3) 2(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)( CH-2-(2-PrO)-5-NO 2-C 6H 3) ( 12). Compounds 1– 6 were active in the polymerization of phenylacetylene. cis-Poly(phenylacetylene) (PPA) was obtained with the rhodium-based catalysts 1, 2, 4– 6, trans-PPA was obtained with the Ir-based catalysts 3 and 8. In addition, compounds 1 and 6 were found to produce highly stereoregular PPA with a cis-content of 100% in the presence of water. Finally, the Ru-based metathesis initiator 12 allowed for the synthesis of trans-PPA, representing the first example of a ruthenium complex being active in the polymerization of a terminal alkyne.

A convenient and simple procedure for the preparation of nitrate esters from alcohols employing LiNO 3/(CF 3CO) 2O

Alcohols in small peptides, monosaccharides and steroids (12 examples) are conveniently transformed to their corresponding nitrate esters upon treatment with an acetonitrile solution of LiNO 3 and trifluoroacetic anhydride. The in situ formed mixed anhydride (CF 3COONO 2) is proposed to be the reactive nitration reagent.

Reactions of the unsaturated triosmium cluster [(μ-H)Os 3(CO) 8(Ph 2PCH 2P(Ph)C 6H 4)] with HX (X = Cl, Br, F, CF 3CO 2,CH 3CO 2): X-ray structures of [(μ-H)Os 3(CO) 7(η 1-Cl)(μ-Cl) 2(μ-dppm)],[(μ-H) 2Os 3(CO) 8(Ph 2PCH 2P(Ph)C 6H 4)] +[CF 3O] − and the two isomers of [(μ-H)Os 3(CO) 8(μ-Cl)(μ-dppm)

Treatment of the electronically unsaturated cluster [(μ-H)Os 3(CO) 8(Ph 2PCH 2P(Ph)C 6H 4)] ( 1) with HCl gas at ambient temperature in dichloromethane afforded (μ-H)Os 3(CO) 8(μ-Cl)(μ-dppm) ( 2) and [(μ-H)Os 3(CO) 7(η 1-Cl)(μ-Cl) 2(μ-dppm)] ( 3). Thermolysis of 2 at 110 °C led to an isomer of 2, 4. A similar reaction of 1 with HBr gas gave [(μ-H)Os 3(CO) 8(μ-Br)(μ-dppm)] ( 5) as the only product which does not isomerize at 110 °C. In sharp contrast, treatment of 1 with HF gas gave the protonated species [(μ-H) 2Os 3(CO) 8(Ph 2PCH 2P(Ph)C 6H 4)] + ( 6). Treatment of 1 with CF 3CO 2H also gave cation 6 whereas CH 3CO 2H yielded [(μ-H)Os 3(CO) 8(μ-η 2-CH 3CO 2)(μ-dppm)] ( 7). Structures of 2, 3, 4 and 6 were established crystallographically. In 2, both the chloride and the hydride ligands simultaneously bridge the same Os–Os edge and the dppm spans another Os–Os bond whereas in 4, all the three ligands bridge the same Os–Os edge. Compound 3 is comprised of an open Os 3 arrangement in which one chloride bridges the open Os⋯Os edge, another chloride and a hydride mutually bridge an Os–Os bond and the third chloride is terminally coordinated to one of the Os atoms of the dppm bridged edge. The cation 6 consists of a triangle of osmium atoms in which the shortest Os–Os edge is bridged by a hydride and the metallated phenyl ring and the longest edge is bridged by another hydride and the diphosphine ligand.

4,4′-Bipyridine and bis(4-pyridyl)propane as bridging ligands in the supramolecular assembly of silver(I) polyhedra containing embedded acetylenediide

Six new silver(I) double salts, namely [Ag 13(C 2) 2(CF 3CO 2) 9(bipy) 4(H 2O) 3] ( 1), [Ag 18(C 2) 2(C 2F 5CO 2) 18(bipyH) 4] · 3H 2O ( 2), [Ag 6(C 2)(CF 3CO 2) 4(bpp)] ( 3), [Ag 6(C 2)(C 2F 5CO 2) 5(bppH)] n ( 4), [Ag 6(C 2)(CF 3CO 2) 5(bppH)] n ( 5) and [Ag 23(C 2) 4(CF 3CO 2) 15(bpp) 6] · H 2O ( 6) (bipy = 4,4′-bipyridine, bpp = bis(4-pyridyl)propane), have been hydrothermally synthesized and structurally characterized. In complex 1, the building units [Ag 24(C 2) 4(CF 3CO 2) 16(H 2O) 6] are connected by bipy ligands to form a two-dimensional network, which are further linked into a three-dimensional architecture via argentophilic interactions. Complex 2 is composed of two independent [Ag(bipyH) 2] 3+cations and a [Ag 16(C 2) 2(C 2F 5CO 2) 18] 6− cluster, whose core is a (C 2) 2@Ag 16 double cage constructed from edge-sharing of two monocapped square antiprisms. Complex 3 has a two-dimensional architecture generated from bpp-bridged silver(I) columns. The virtually iso-structural complexes 4 and 5 each has a branched-tree architecture. The backbone is composed of fused silver(I) double cages, with C 2 2 - species embedded in its stem and an exterior coat comprising anionic perfluorocarboxyate and protonated bpp ligands. Complex 6 exhibits a two-dimensional architecture in which the basic building unit is an unusual silver(I) column composed of four consecutively fused C 2@Ag n cages.

Addition of secondary amines to activated alkenes promoted by Pd(II) complexes: Use of ammonium salts as cocatalysts

The complexes [Pd(acac) 2] 1, [Pd(hfa) 2] 2 (hfa = hexafluoroacetylacetonate), [Pd(CF 3CO 2) 2] 3 and [Pd 3(CH 3CO 2) 6] 4 exhibit very different catalytic efficiency in the reaction between secondary amines and activated alkenes. Complexes 1 and 4 generally show an enhanced activity when catalytic amounts of NH 4X salts (X − = low-coordinating anion) are added to the reaction mixtures. On the contrary, the activity of the perfluorurate analogues 2 and 3, which is much higher than that of 1 and 4, is generally scarcely affected by the presence of the NH 4X additive. The cocatalytic effect of NH 4X is comparable with that of strong acids such as CF 3SO 3H. The ammonium salts alone can behave as a catalyst giving an almost quantitative yield of the hydroamination product.

Hemiacetal and hemiaminal formation at fluoroacyl moiety

Hemiacetals and hemiaminals were produced not only at a trifluoroacetyl (CF 3CO) moiety but also at difluoroacetyl (CHF 2CO) and pentafluoroalkanoyl (C 2F 5CO) moieties. As larger was the electron-withdrawing nature and less bulky was the fluoroalkyl (R f) group and smaller was the size of an alcohol, the ratio of hemiacetal form increased. Not only a CF 3CO moiety but also monofluoroacetyl (CH 2FCO), CHF 2CO, and C 2F 5CO moieties produced the hemiaminals. As larger was the electron-withdrawing nature of R f group and smaller was an amine, the ratio of hemiaminal form increased.

Molecular structure of simple mono- and diphenyl meso-substituted porphyrin diacids: influence of protonation and substitution on the distorsion

The crystal and molecular structures of three simple porphyrin diacids have been determined from X-ray diffraction data to delineate how the peripheral substituents of the porphyrin affect the overall molecular flexibility. Di- meso-substituted [DPPH 4] 2+(CF 3CO 2 −) 2 and, mono- meso-substituted [MPPH 4] 2+(CF 3CO 2 −) 2 and [dedmMPPH 4] 2+(CF 3CO 2 −) 2 porphyrin diacids show increasingly saddled core conformation. Some of the spectroscopic properties (NMR and UV–visible) of the porphyrin diacids are also discussed in terms of the observed structures.

Synthesis of alkyl and aryl C-pyranosides using organozinc reagents via a Ferrier-type rearrangement

The reaction of 1,2-dihydropyranyl acetates with dimethylzinc, diethylzinc and diphenylzinc in the presence of CF 3COOH gave the corresponding alky and aryl C-pyranosides via a Ferrier rearrangement in excellent yields. Use of the organozinc species, CF 3CO 2ZnPh, reacted with high stereoselectivity to give the phenyl C-glycosides. Arylzinc chlorides could also be successfully applied to this reaction in the presence of BF 3·OEt 2.

Synthesis, molecular structure, substitution and C–C coupling reactions of ruthenium complexes containing (η 5-C 9H 7)Ru(PPh 3) as a molecular unit

The 2-methallyl complex [(η 5-C 9H 7)Ru(η 3-2-MeC 3H 4)(PPh 3)] ( 3), prepared from [(η 5-C 9H 7)Ru(PPh 3) 2Cl] ( 2) and 2-MeC 3H 4MgCl, reacts with HX (X = Cl, CF 3CO 2) in the presence of ethene to give the chiral-at-metal compounds [(η 5-C 9H 7)Ru(C 2H 4)(PPh 3)X] ( 4, 5) in nearly quantitative yields. Treatment of 2 with AgPF 6 and ethene affords [(η 5-C 9H 7)Ru(C 2H 4)(PPh 3) 2]PF 6 ( 6), which reacts with acetone to give the substitution product [(η 5-C 9H 7)Ru(OCMe 2)(PPh 3) 2]PF 6 ( 7). The molecular structure of 7 has been determined crystallographically. Whereas treatment of 4 with CH(CO 2Et)N 2 yields the olefin complex [(η 5-C 9H 7)Ru{η 2-( Z)-C 2H 2(CO 2Et) 2}(PPh 3)Cl] ( 8), the reactions of 4 and 5 with Ph 2CN 2, PhCHN 2 and (Me 3Si)CHN 2 lead to the formation of the carbeneruthenium(II) derivatives [(η 5-C 9H 7)Ru( CRR′)(PPh 3)Cl] ( 9– 11) and [(η 5-C 9H 7)Ru( CRR′)(PPh 3)(κ 1-O 2CCF 3)] ( 12– 14), respectively. Treatment of 9 (R = R′ = Ph), 10 (R = H, R′ = Ph) and 11 (R = H, R′ = SiMe 3) with MeLi produces the hydrido(olefin) complexes [(η 5–C 9H 7)RuH(η 2-CH 2 CPh 2)(PPh 3)] ( 15), [(η 5-C 9H 7)RuH(η 2-CH 2 CHPh)(PPh 3)] ( 18a, b) and [(η 5-C 9H 7)RuH(η 2-CH 2 CHSiMe 3)(PPh 3)] ( 19) via C–C coupling and β-hydride shift. The analogous reactions of 11 with PhLi gives the η 3-benzyl compound [(η 5-C 9H 7)Ru{η 3-(Me 3Si)CHC 6H 5}(PPh 3)] ( 20). The η 3-allyl complex [(η 5-C 9H 7)Ru(η 3-1-PhC 3H 4)(PPh 3)] ( 17) was prepared from 10 and CH 2 CHMgBr by nucleophilic attack.

Interplay between aminoalcohols and trifluoroacetate ligands: Ba–Cu heterometallics or cocrystallization of homometallics?

The reaction between copper powder and Ba(TFA) 2 (TFA = CF 3CO 2) in methanol under air and in the presence of an aminoalcohol, afforded Cu(II) alkoxides and subsequent formation of heterometallic species or cocrystallization depending on the functional alcohol, dimethylaminoethanol (dmeaH) or N-dimethylaminoethanol (mdeaH 2), respectively. A 1D-coordination polymer [Ba 3Cu 2(μ,η 2-TFA) 6(μ,η 2-OC 2H 4NMe 2) 4(MeOH) 2,2MeOH] ∞, based on zig–zag chains was obtained with dmeaH, whereas mdeaH 2 lead to [Ba(η 1-TFA) 2{MeN(C 2H 4OH) 2} 2] 2a and [Cu{MeN(C 2H 4O)(C 2H 4OH)} 2] (2b) which cocrystallize as two independent molecules in the asymmetric unit cell.

Novel addition in trifluoromethylation of [70]fullerene

Pyrolytic trifluoromethylation of [70]fullerene with CF 3CO 2Ag at 300 °C results in the addition of up to 12 CF 3 groups to the fullerene cage. Forty-six C 70(CF 3) n derivatives (numbers in parentheses) were separated by two-stage high pressure liquid chromatography (HPLC) as follows: n = 2(2), 4(16), 6(9), 8(14) 10(5), some being characterised by 19 F NMR. The range of derivatives is much greater than for other [70]fullerene reactions, and as with [60]fullerene trifluoromethylation, no single derivative is dominant, indicating that kinetic stability mainly controls product formation. 19 F NMR spectra show most derivatives to be unsymmetrical, with combinations of quartets and septets (overlapping quartets) due to contiguous (‘linear’) addend arrays, having significantly different coupling constants of the ‘terminal’ quartets of between 9.1 and 17.7 Hz. These differences, together with those observed previously in trifluoromethylation of [60]fullerene are consistent with addition across both 6:6- and 5:6-ring junctions. Of the two C 70(CF 3) 2 isomers, one has either C s or C 2 symmetry, the other has C 1 symmetry, whilst the C 70(CF 3) 4 derivatives fall into four categories: (i) symmetrical compounds (one gives only two singlets in the 19 F NMR); (ii) unsymmetrical compounds that show a ‘linear’ coupling sequence; (iii) unsymmetrical compounds having a remote pairs of adjacent groups; (iv) compounds having a coupled array of three CF 3 groups, together with a remote group suggesting sterically-driven migration. The first evaluation of differential NMR couplings across 6:6- and 5:6-bonds in a fullerene has been made using C 60F 6 as a model.

Polyethercarbonate–silica nanocomposites synthesized by copolymerization of allyl glycidyl ether with CO 2 followed by sol–gel process

The catalyst system consisting of Y(CF 3CO 2) 3, Zn(Et) 2, and pyrogallol in the solvent of 1,3-dioxolane was found to be effective for the copolymerization of allyl glycidyl ether with carbon dioxide at 60 °C and 400 psi. The IR, 1H-NMR, and 13C-NMR spectra as well as the element analysis indicated that the resulting copolymer was an alternating polyethercarbonate with the carbonate content higher than 97.5%. The resulting polyethercarbonate could react with 3-(trimethoxysilyl)propyl methacrylate via a free radical reaction to generate the alkoxysilane-containing copolymer precursors that were used in the subsequent sol–gel process to result in the polyethercarbonate–silica nanocomposite. The generated nanocomposite was characterized by 13C-NMR, 29Si-NMR, SEM, DSC, TGA, ESCA, and UV–Vis. The mechanical properties were also measured. A good compatibility between polyethercarbonate and silica and a SiO 2 network with silica particles less than 100 nm in the nanocomposite were observed. Both the thermal and mechanical properties of the resulting polyethercarbonate–silica nanocomposite were found to enhance with silica content. The optical transparency of the generated nanocomposite was comparable to that of the based polyethercarbonate.