Protonation of gas-phase aromatic molecules: IR spectrum of the fluoronium isomer of protonated fluorobenzene

The IR spectrum of the fluoronium isomer of protonated fluorobenzene (F-C(6)H(6)F(+), phenylfluoronium) is recorded in the vicinity of the C-H and F-H stretch fundamentals to obtain the first structured spectrum of an isolated protonated aromatic molecule in the gas phase. Stable F-C(6)H(6)F(+) ions are produced via proton transfer from CH(5)(+) to fluorobenzene (C(6)H(5)F) in a supersonic plasma expansion. The F-C(6)H(6)F(+) spectrum recorded between 2,540 and 4,050 cm(-1) is consistent with a weakly bound ion-dipole complex composed of HF and the phenyl cation, HF-C(6)H(5)(+). The strongest transition occurs at 3,645 cm(-1) and is assigned to the F-H stretch (sigma(FH)). The antisymmetric C-H stretch of the two ortho hydrogen atoms, sigma(CH) = 3,125 cm(-1), is nearly unshifted from bare C(6)H(5)(+), indicating that HF complexation has little influence on the C-H bond strength of C(6)H(5)(+). Despite the simultaneous production of the more stable ring protonated carbenium isomers of C(6)H(6)F(+) (fluorobenzenium) in the electron ionization source, F-C(6)H(6)F(+) can selectively be photodissociated into C(6)H(5)(+) and HF under the present experimental conditions, because it has a much lower dissociation energy than all carbenium isomers. Quantum chemical calculations at the B3LYP and MP2 levels of theory using the 6-311G(2df,2pd) basis support the interpretation of the experimental data and provide further details on structural, energetic, and vibrational properties of F-C(6)H(6)F(+), the carbenium isomers of C(6)H(6)F(+), and other weakly bound HF-C(6)H(5)(+) ion-dipole complexes. The dissociation energy of F-C(6)H(6)F(+) with respect to dehydrofluorination is calculated as D(0) = 4521 cm(-1) (approximately 54 kJ/mol). Analysis of the charge distribution in F-C(6)H(6)F(+) supports the notation of a HF-C(6)H(5)(+) ion-dipole complex, with nearly the whole positive charge of the added proton distributed over the C(6)H(5)(+) ring. As a result, protonation at the F atom strongly destabilizes the C-F bond in C(6)H(5)F.     

Synthesis, structure, and dynamics of six-membered metallacoronands and metallodendrimers of iron and indium

In the reaction of the N-substituted diethanolamines (H(2)L(1-3)) (1-3) with calcium hydride followed by addition of iron(III) or indium(III) chloride, the iron wheels [Fe(6)Cl(6)(L(1))(6)] (4) and [Fe(6)Cl(6)(L(2))(6)] (6) or indium wheels [In(6)Cl(6)(L(1))(6)] (5), [In(6)Cl(6)(L(2))(6)] (8) and [In(6)Cl(6)(L(3))(6)] (9) were formed in excellent yields. Exchange of the chloride ions of 6 by thiocyanate ions afforded [Fe(6)(SCN)(6)(L(2))(6)] (7). Whereas the structures of 4, 5 and 7 were determined unequivocally by single-crystal X-ray analyses, complexes 8 and 9 were characterised by NMR spectroscopy. Contrary to what is normally presumed, the scaffolds of six-membered metallic wheels are not generally rigid, but rather undergo nondissociative topomerisation processes. This was shown by variable temperature (VT) (1)H NMR spectroscopy for the indium wheel [In(6)Cl(6)(L(1))(6)] (5) and is highlighted for the enantiotopomerisation of one indium centre [ 1/6[S(6)-5]<==>[1/6[S(6)-5']]. The self-assembly of metallic wheels, starting from diethanolamine dendrons, is an efficient strategy for the convergent synthesis of metallodendrimers.     

A comparative study of the structures and reactivity of cyclometallated platinum compounds of N-benzylidenebenzylamines and cycloplatination of a primary amine

The reaction of cis-[PtCl(2)(dmso)2] with ligands 4-ClC(6)H(4)CHNCH(2)C(6)H(5) (1a) and 4-ClC(6)H(4)CHNCH(2)(4-ClC(6)H(4)) (1b) in the presence of sodium acetate and using either methanol or toluene as solvent produced the corresponding five-membered endo-metallacycles [PtCl{(4-ClC(6)H(3))CHNCH(2)C(6)H(5)}{SOMe(2)}] (2a) and [PtCl{(4-ClC(6)H(3))CHNCH(2)(4'-ClC(6)H(4))}{SOMe(2)}] (2b). An analogous reaction for ligands 2,6-Cl(2)C(6)H(3)CHNCH(2)C(6)H(5) (1c) and 2,6-Cl(2)C(6)H(3)CHNCH(2)(4-ClC(6)H(4)) (1d) produced five-membered exo-metallacycles [PtCl{(2,6-Cl(2)C(6)H(3))CHNCH(2)C(6)H(4)}{SOMe(2)}] (2c) and [PtCl{(2,6-Cl(2)C(6)H(3))CHNCH(2)(4'-ClC(6)H(3))}{SOMe(2)}] (2d) when the reaction was carried out in methanol and seven-membered endo-platinacycles [PtCl{(MeC(6)H(3))ClC(6)H(3)CHNCH(2)C(6)H(4)}{SOMe(2)}] (3c) and [PtCl{(MeC(6)H(3))ClC(6)H(3)CHNCH(2)(4'-ClC(6)H(3))}{SOMe(2)}] (3d) when toluene was used as a solvent. The reaction of 2,4,6-(CH(3))(3)C(6)H(2)CHNCH(2)(4-ClC(6)H(4)) (1e) produced in both solvents an exo-platinacycle [PtCl{(2,4,6-(CH(3))(3)C(6)H(2))CHNCH(2)(4'-ClC(6)H(3))}{SO(CH(3))(2)}] (2e). Cyclometallation of 4-chlorobenzylamine was also achieved to produce compound [PtCl{(4-ClC(6)H(3))CH(2)NH(2)}{SOMe(2)}] (2g). The reactions of endo- and exo-metallacycles with phosphines evidenced the higher lability of the Pt-N bond in exo-metallacycles while a comparative analysis of the crystal structures points out a certain degree of aromaticity in the endo-metallacycle.     

Preparation of three positional isomers of diglucosyl-cyclomaltohexaose.

Three positional isomers of diglucosyl-cyclomaltohexaose (diglucosyl-cG6) were chemically synthesized via 6(1),6(2)-, 6(1),6(3)-, and 6(1),6(4)-di-O-(TERT-butyldimethylsilyl)-cG6S (1, 2, and 3) prepared regiospecifically. Glucosylation of bis(2,3-di-O-acetyl)tetrakis(2,3,6-tri-O-acetyl)-CG6S obtained from the three regioisomeric compounds 1, 2, and 3 with 2,3,4,6-tetra-O-benzyl-1-O-trichloroacetimidoyl-alpha-D-glucopyran ose, followed by debenzylation and then deacetylation, afforded 6(1),6(2)-, 6(1),6(3)-, and 6(1),6(4)-di-O-(alpha-D-glucopyranosyl)-cG6S (10, 11, and 12) together with configurational isomers. The desired compounds 10, 11, and 12 containing two (1----6)-alpha-linkages were isolated from the mixtures of their configurational isomers by high performance liquid chromatography. The three diglucosyl-cG6S synthesized chemically were used as authentic samples to identify the components in a mixture of diglucosyl-cG6S produced by an enzymatic process.     

Excision of the

The synthesis of new molybdenum cluster selenocyanide anionic complexes [Mo6Se8(CN)6]7- and [Mo6Se8(CN)6]6- is reported. The [Mo6Se8(CN)6]7- ion was obtained by excision of the cluster core [Mo6Se8] from a Chevrel phase in the reaction of Mo6Se8 with KCN at 650 degrees C; the [Mo6Se8(CN)6]6- ion is formed by oxidation of [Mo6Se8(CN)6]7-. New cluster salts K7[Mo6Se8(CN)6] x 8H2O (1) and (Me4N)4K2[Mo6Se8(CN)6] x 10H2O (2) were isolated and their crystal structures were solved. Compound 1 crystallizes in the cubic space group Fm3m (a=15.552(2) A, Z=4, V=3761.5(8) A3), compound 2 crystallizes in the triclinic space group P1 (a=11.706(2), b=11.749(2), c=12.459(2) A, alpha=72.25(1), beta=77.51(1), gamma=63.04(1), Z=1, V=1448.5(4) A3). Compound 1 is paramagnetic due to an availability of 21 electrons per Mo6 cluster; cyclic voltammetry reveals a quasi-reversible transition [Mo6Se8(CN)6]7- <--> [Mo6Se8(CN)6]6-, E1/2=0.63 V.     

Spectrophotometric Study of the Complexation of Some Lanthanide (III) Ions with a Series of 18-Crowns-6 in DMSO Solution Using Murexide as a Metallochromic Indicator

The complexation of La(III), Ce(III), Pr(III) and Er(III) with 18-crown-6(18C6), dibenzo-18-crown-6 (DB18C6), dicyclohexano-18-crown-6 (DCY18C6) anddibenzopyridino-18-crown-6 (DBPY18C6) has been studied in dimethylsulfoxide(DMSO) by means of a competitive spectrophotometric method using murexide asa metal ion indicator. The formation constants of the 1 : 1 complexeswere found tovary in the order La(III) > Ce(III) > Pr(III) > Er(III). It was foundthat the structure influences the formation and stability of the resultingcomplexes. The effects ofvarious parameters on complexation are discussed. The order of the stabilityconstants of each lanthanide ion with these macrocycles are18C6 > DC18C6 > DB18C6 > DBPY18C6.     

GSH对两种谷胱甘肽过氧化物酶模拟物活性影响的研究

设计并合成了谷胱甘肽过氧化物酶(GPX)模拟物6A,6A’-二苯胺-6B,6B’-二硒桥联-β-环糊精(6-AnSeCD). 采用双酶偶联法测定GPX的活力结果显示, 6A,6A’-二环己胺-6B,6B’-二硒桥联-β-环糊精(6-CySeCD)催化谷胱甘肽还原H2O2和枯烯H2O2的活力均比6-AnSeCD的高. 为了进一步考察6-CySeCD和6-AnSeCD与GSH之间的相互作用, 进行了分子动力学(MD)模拟和分子对接研究. 结果表明, 与GSH的结合使GPX模拟物的构象发生变化, 这种改变可能是影响桥连GPX模拟物催化活性的关键因素.     

Arachno, nido, and closo aromatic isomers of the Li6B6H6 molecule

We analyzed chemical bonding in low-lying isomers of the recently computationally predicted B(6)H(6)Li(6) molecule. According to our calculations the benzene-like B(6)H(6)Li(6) (D(2h), (1)A(1g)) arachno structure with the planar aromatic B(6)H(6)(6-) anion is the most stable one. A nido isomer with two aromatic B(6)H(6)(4-) (pentagonal pyramid) and Li(3)(+) (triangular) moieties, which can be considered as derived from the global minimum structure through a two-electron intramolecular transfer from B(6)H(6)(6-) to three Li(+) cations, was found to be 10.7 kcal/mol higher in energy. A closo isomer with three aromatic moieties (octahedral B(6)H(6)(2-) and two Li(3)(+)) was found to be 31.3 kcal/mol higher in energy than the global minimum. Another isomer with three aromatic moieties (two B(3)H(3)(2-) and Li(3)(+)) was found to be substantially higher in energy (74.4 kcal/mol). Thus, the intramolecular electron transfers from the highly charged B(6)H(6)(6-) anion to cations are not favorable for the B(6)H(6)Li(6) molecule, even when a formation of three-dimensional aromatic B(6)H(6)(2-) anion and two sigma-aromatic Li(3)(+) cations occurs in the closo isomer.     

Arene-ruthenium complexes of an acyclic thiolate-thioether and tridentate thioether derivatives resulting from ring-closure reactions

The reaction of [(eta(6)-arene)RuCl(2)](2) (arene = C(6)Me(6), 1,4-MeC(6)H(4)CHMe(2)) with a large excess of the dianion of bis(2-mercaptoethyl) sulfide, (HSCH(2)CH(2))(2)S, obtained from deprotonation of the dithiol with freshly prepared NaOMe, gives the deep red, monomeric complexes [(eta(6)-arene)Ru(eta(3)-C(4)H(8)S(3))] (arene = C(6)Me(6) (5), 1,4-MeC(6)H(4)CHMe(2) (6)) in which the dianion is bound to the metal atom through one thioether and two thiolate sulfur atoms. Complex 5 reacts with [(eta(6)-C(6)Me(6))RuCl(2)](2) (4) in a 2:1 mole ratio to give a quantitative yield of the chloride salt of a binuclear cation [((eta(6)-C(6)Me(6))Ru)(2)Cl(mu(2)-eta(2):eta(3)-C(4)H(8)S(3))](+) (7) in which the thiolate sulfur atoms of the [(eta(6)-C(6)Me(6))Ru(eta(3)-C(4)H(8)S(3))] group bridge to a (eta(6)-C(6)Me(6))RuCl unit. This compound is also obtained directly from the reaction of 4 with the dithiolate, if the Ru dimer is used in large excess. The binuclear complex [((eta(6)-C(6)Me(6))Ru)(2)(MeCN)(mu(2)-eta(2):eta(3)-C(4)H(8)S(3))](PF(6))(2).MeCN, (9)(PF(6))(2).MeCN, is obtained by treatment of (7)Cl with NH(4)PF(6) in acetonitrile. Protonation of 5 with HCl gave the mono- and diprotonated derivatives viz. [(eta(6)-C(6)Me(6))Ru(eta(3)-C(4)H(9)S(3))]Cl, (8)Cl, and [(eta(6)-C(6)Me(6))Ru(eta(3)-C(4)H(10)S(3))]Cl(2), (10)Cl(2), respectively. The reaction of 5 with methyl iodide gives both the mono- and di-S-methylated derivatives. Treatment of 5 with dibromoalkanes, Br(CH(2))(n)Br (n = 1-5), effects ring closure to give the (eta(6)-C(6)Me(6))Ru dications containing the trithia mesocyclic zS3 (z = 8-12) ligands, isolated as their PF(6) salts. The X-ray crystal structures of 5, 6, the solvates of (7)Cl and (9)(PF(6))(2), and the trithia mesocyclic Ru complexes (eta(6)-C(6)Me(6))Ru(zS3)(PF(6))(2) (z = 8-11) are reported.     

Homoleptic organometallic anions of Ti, Zr, Hf, and Nb

Reactions of C(6)H(5)Li and 4-CH(3)C(6)H(4)Li with halides of Ti, Ir, Hf, and Nb lead to the formation of homoleptic organometallic anions of these metals. Owing to their thermal instability and their sensitivity towards H(2) O and O(2) , these compounds are characterized by single-crystal structure determinations at low temperature, whereas other physical data could only be obtained occasionally. Three pentacoordinate complex anions [Ti(C(6)H(5))(5)](-), [Ti(4-CH(3)C(6)H(4))(5)](-), and [Zr(C(6)H(5))(5)](-) have square-pyramidal structures that display only slight deviations from the ideal geometry, in contrast to the already known structures of [Ti(CH(5))(5)](-). The hexacoordinate complex anions [Zr(C(6)H(5))(6)](2-), [Zr(4-CH(3)C(6)H(4))(6)](2-), [Nb(C(6)H(5))(6)](2-), and [Nb(4-CH(3)C(6)H(4))(6)](2-) all have trigonal-prismatic structures, in accord with the known hexamethyl complex dianions. In contrast, the hexacoordinate complex anion [Hf(C(6)H(5))(6)](2)(-) has an octahedral or close to octahedral structure, in contrast to the known trigonal-prismatic structures of [Ta(C(6)H(5))(6)](-) and [Ta(4-CH(3)C(6)H(4))(6) (-). A qualitative explanation for this structural variability is given.     

Reactions of platinum cluster ions with benzene

In this work, the cation and anion products of the reactions between platinum clusters produced by laser ablation and the benzene molecules seeded in argon have been studied using a high-resolution reflectron time-of-flight mass spectrometer (RTOFMS). The dominant cation products are [C(6n)H(6n - k)](+) and [Pt(m)(C(6)H(6))(n)](+) complexes, while the dominant anion products are dehydrogenated species, [C(6)H(5)PtH](-), [PtC(12)H(k)](-) and [Pt(m)C(6)H(4) . . . (C(6)H(6))(n)](-), etc. Some important intermediate structures ([PtC(6)H(6)](+), [Pt(C(6)H(6))(2)](+), [Pt(2)(C(6)H(6))(3)](+), [C(6)H(5)PtH](-), [Pt(2)C(6)H(4)](-), [Pt(3)C(6)H(4)](-) and [Pt(4)C(6)H(4)](-)) have been analyzed using density functional theory (DFT) calculations. Different reaction mechanisms are proposed for platinum cluster cations and anions with benzene, respectively.     

Synthesis and reactivity of {Ru(p-cymene)}2+ derivatives of [Nb6O19]8-: a rational approach towards fluxional organometallic derivatives of polyoxometalates

Three {Ru(p-cym)}(2+) (p-cym = p-cymene) derivatives of [Nb(6)O(19)](8-)-[Nb(6)O(19){Ru(p-cym)}](6-) (Nb(6)Ru(1)), trans-[Nb(6)O(19){Ru(p-cym)}(2)](4-) (t-Nb6Ru2), and [Nb(6)O(19){Ru(p-cym)}(4)] (Nb(6)Ru(4))--have been synthesized in water by reaction between [Ru(p-cym)Cl(2)](2) and the hexaniobate. In the solid state, Nb(6)Ru(1) and Nb(6)Ru(4) have been characterized by IR and EDX spectroscopies, whereas t-Nb(6)Ru(2) has been characterized by IR spectroscopy and single-crystal X-ray diffraction (crystal data for K(4)-trans-[Nb(6)O(19){Ru(p-cym)}(2)].14H(2)O (K(4)-t-Nb(6)Ru(2).14H(2)O). In solution, all compounds were characterized by (1)H NMR and ESI mass spectrometry analyses, and Nb(6)Ru(1) was also analyzed by (17)O NMR. These studies allowed a comparison of the differences in behaviour of the three complexes in water: Nb(6)Ru(1) is particularly stable, Nb(6)Ru(4) decomposes by loss of {Ru(p-cym)}(2+) fragments, and trans-[Nb(6)O(19){Ru(p-cym)}(2)](4-) isomerizes into cis-[Nb(6)O(19){Ru(p-cym)}(2)](4-). A rational mechanism for the isomerisation of t-Nb(6)Ru(2) is proposed on the basis of a kinetic study.     

Synthesis and Characterization of Sterically Encumbered Derivatives of Aluminum Hydrides and Halides: Assessment of Steric Properties of Bulky Terphenyl Ligands

The synthesis and characterization of several sterically encumbered monoterphenyl derivatives of aluminum halides and aluminum hydrides are described. These compounds are [2,6-Mes(2)C(6)H(3)AlH(3)LiOEt(2)](n)() (1), (Mes = 2,4,6-Me(3)C(6)H(2)-), 2,6-Mes(2)C(6)H(3)AlH(2)OEt(2) (2), [2,6-Mes(2)C(6)H(3)AlH(2)](2) (3), 2,6-Mes(2)C(6)H(3)AlCl(2)OEt(2) (4), [2,6-Mes(2)C(6)H(3)AlCl(3)LiOEt(2)](n)() (5), [2,6-Mes(2)C(6)H(3)AlCl(2)](2) (6), TriphAlBr(2)OEt(2) (7), (Triph = 2,4,6-Ph(3)C(6)H(2)-), [2,6-Trip(2)C(6)H(3)AlH(3)LiOEt(2)](2) (8) (Trip = 2,4,6-i-Pr(3)C(6)H(2)-), 2,6-Trip(2)C(6)H(3)AlH(2)OEt(2) (9), [2,6-Trip(2)C(6)H(3)AlH(2)](2) (10), 2,6-Trip(2)C(6)H(3)AlCl(2)OEt(2) (11), and the partially hydrolyzed derivative [2,6-Trip(2)C(6)H(3)Al(Cl)(0.68)(H)(0.32)(&mgr;-OH)](2).2C(6)H(6) (12). The structures of 2, 3a, 4, 6, 7, 9a, 10a, 10b, 11, and 12 were determined by X-ray crystallography. The structures of 3a, 9a, 10a, and 10b, are related to 3, 9, and 10, respectively, by partial occupation of chloride or hydride by hydroxide. The compounds were also characterized by (1)H, (13)C, (7)Li, and (27)Al NMR and IR spectroscopy. The major conclusions from the experimental data are that a single ortho terphenyl substituent of the kind reported here are not as effective as the ligand Mes (Mes = 2,4,6-t-Bu(3)C(6)H(2)-) in preventing further coordination and/or aggregation involving the aluminum centers. In effect, one terphenyl ligand is not as successful as a Mes substituent in masking the metal through agostic and/or steric effects.     

Formation and structures of mercury complexes of 18-membered unsaturated and saturated thiacrown ethers

The complexation of 18-membered unsaturated thiacrown ether, 18-UT-6, with 1 equiv of HgCl(2) in acetone afforded mercury complex Hg(II)(18-UT-6)Cl(2). The complexations of 18-membered saturated thiacrown ether, 18S6, with 1 equiv each of HgCl(2) and CdCl(2) in acetone afforded Hg(II)(18S6)Cl(2) and Cd(II)(18S6)Cl(2), respectively. The crystal structure of Hg(II)(18-UT-6)Cl(2) revealed that the mercury atom was inside the cavity of the macrocycle and the geometry around the mercury atom was an eight-coordinate hexagonal bipyramidal arrangement. ORTEP drawing of Hg(II)(18S6)Cl(2) revealed the existence of the mercury atom outside the cavity of the ring, as well as a polymeric chain structure. (1)H NMR study of Hg(II)(18-UT-6)Cl(2) in acetone-d(6) indicated that the interconversion between free 18-UT-6 and pure complex was slower than the NMR time scale. The titration experiment by (1)H NMR revealed that 18-UT-6 had inclusion selectivity for the number of mercury atoms. The electrochemical behavior of complexes Hg(II)(18-UT-6)Cl(2) and Hg(II)(18S6)Cl(2) was also examined.     

Reaction of m-terphenyldichlorophosphanes with sodium azide: synthesis and characterization of stable azidocyclophosphazenes

Reaction of the m-terphenyldichlorophosphanes 2,6-(2-MeC(6)H(4))(2)C(6)H(3)PCl(2) (1), 2,6-(4-t-BuC(6)H(4))(2)C(6)H(3)PCl(2) (2), or 2,6-Mes(2)C(6)H(3)PCl(2) (3) with excess NaN(3) in acetonitrile at room temperature afforded the corresponding bisazidophosphanes 2,6-(2-MeC(6)H(4))(2)C(6)H(3)P(N(3))(2), 2,6-(4-t-BuC(6)H(4))(2)C(6)H(3)P(N(3))(2) (5), or 2,6-Mes(2)C(6)H(3)P(N(3))(2) (6) (Mes = 2,4,6-Me(3)C(6)H(2)), respectively. These compounds are thermally labile and decompose into a number of azidophosphazenes. The azidocyclophosphazenes [NP(N(3))(C(6)H(3)(4-t-BuC(6)H(4))(2)-2,6)](3) (4) and [NP(N(3))C(6)H(3)Mes(2)-2,6](2) (8) have been isolated from these mixtures. All compounds were characterized by (1)H, (13)C, (31)P NMR and IR spectroscopy. Crystal structures of 2, 4, and 8 were determined.     

Formation of single-bonded (C60-)2 and (C70-)2 dimers in crystalline ionic complexes of fullerenes

New ionic complexes of fullerenes C(60) and C(70) with decamethylchromocene Cp*(2)Cr.C60.(C(6)H(4)Cl(2))(2) (1), Cp*(2)Cr.C60.(C(6)H(6))(2) (2); the multicomponent complex of (Cs(+))(C70-) with cyclotriveratrylene CTV.(Cs)(2).(C70)(2).(DMF)(7).(C(6)H(6))(0.75) (3); bis(benzene)chromium Cr(C(6)H(6))(2).C60.(C(6)H(4)Cl(2))(0.7) (4), Cr(C(6)H(6))(2).C60.C(6)H(5)CN (5), Cr(C(6)H(6))(2).C70.C(6)H(4)Cl(2) (6), Cr(C(6)H(6))(2).C60 (7); cobaltocene Cp(2)Co.C60.C(6)H(4)Cl(2) (8), Cp(2)Co.C70.(C(6)H(4)Cl(2))(0.5) (9); and cesium Cs.C70.(DMF)(5) (10) have been obtained. The complexes have been characterized by the elemental analysis, IR-, UV-vis-NIR spectroscopy, EPR and SQUID measurements. It is shown that C(60)(.-) exists as a single-bonded diamagnetic (C60-)2 dimer in 1, 2, 4, 5, and 8 at low temperatures (1.9-250 K). The dimers dissociate above 160-250 K depending on donor and solvent molecules involved in the complex. C60(.-) dimerizes reversibly and shows a small hysteresis (<2 K) at slow cooling and heating rates. The single-bonded diamagnetic (C70-)2 dimers are also formed in 6, 9, and 10 and begin to dissociate only above 250-360 K. The IR and UV-vis-NIR spectra of sigma-bonded negatively charged fullerenes are presented.     

Synthesis and study of hexanuclear molybdenum clusters containing thiolate ligands

Four hexanuclear molybdenum chloride cluster complexes containing terminal thiolate ligands have been synthesized and fully characterized. (Bu 4N) 2[Mo 6Cl 8(SEt) 6] was prepared by reacting Na 2[Mo 6Cl 8(OMe) 6] with an excess of ethanethiol in refluxing tetrahydrofuran. (PPN) 2[Mo 6Cl 8(SBu) 6], (Bu 4N) 2[Mo 6Cl 8(SBn) 6], and (Bu 4N) 2[Mo 6Cl 8(SNC 8H 6) 6] (C 8H 6NS (-) = 3-indolylthiolate) were subsequently prepared in the reaction of [Mo 6Cl 8(SEt) 6] (2-) with an excess of HSR (R = Bu, Bn or 3-indolyl). Single crystal X-ray diffraction analyses were performed on two of these complexes: (PPN) 2[Mo 6Cl 8(SEt) 6].Et 2O, crystallizes in the triclinic space group P1 with a = 12.3894(11), b = 13.7651(12), c = 15.0974(13), alpha = 103.975(2), beta = 99.690(2), gamma = 98.062(2), and Z = 1; (PPh 3Me) 2[Mo 6Cl 8(SBn) 6].2NO 2CH 3, also crystallizes in the P1 space group with a = 12.1574(16), b = 13.4441(17), c = 14.2132(18), alpha = 89.654(2), beta = 88.365(2), gamma = 71.179(2), and Z = 1. Our studies demonstrate that [Mo 6Cl 8(SEt) 6] (2-) displays luminescent properties and that the same complex undergoes substitution reactions with different thiols, as well as reaction with electrophilic reagents such as MeI.     

C_(70)与臭氧反应机理的理论研究

用半经验AM1方法研究了C_(70)与臭氧环加成反应的反应机理。采用Berny梯度 法优化得到反应的过滤度，并进行了振动分析确诊。计算结果表明：臭氧在C_(70) 6－6单、双键上的环加成反应均为复杂反应，由三步组成：第一步是O_3分子与C_ (70)的6-6单、双键发生1,3-偶极环加成反应，生成分子臭氧化物（即中间体I）， 6－6双键加成为放热反应，6－6单键加成为吸热反应，活化势垒分别为84.7和181. 2 kJ·mol~(-1)；第二步是中间体I的加成，C－C键断裂，生成两性离子中间体II 的放热反应，其势垒分别为61.3和13.3 kJ·mol~(-1)；第三步是中间体II脱去一 个Q_2分子生成具有环氧结构的C_(70)O，均为放热反应，活化势垒分别为169.3和 101.2 kJ·mol~(-1)；第三步是中间体I脱去一个O_2分子生成具有环氧结构的C_ (70)O，均为放热反应，活化势垒分别为169.3和101.2 kJ·mol~(-1)，从反应机理 和动力学角度解释了6－6双键加成优于6-6双键加成优于6-6双键加成优于6-6单键 加成的原因。O_3分子与C_(70)6-6双键的加成反应是协同且同步进行的，与6－6单 键的加成反应是协同但不同步的过程。     

2 + 2] cross coupling of benzene and tropylium ligands in reductively activated piano stool complexes of Mn,Cr, and W

We have established cation/anion coupling reactions between the tropylium ligand in [M(eta7-C7H7)(CO)3]+ (M = Cr, W) and the reductively activated eta4-benzene ligand in [Mn(eta4-C6H6)(CO)3]- (3-) to form [M(CO)3(mu2-eta6:eta5-C7H7-C6H6)Mn(CO)3]; [Cr(CO)3(mu2-eta6:eta5-C7H7-C6H6)Mn(CO)3] can be further reduced to [Cr(CO)3(mu2-eta5:eta4-C7H7-C6H6)Mn(CO)3]2-, in which the tropylium and benzene ligands have undergone a [2 + 2] cross coupling reaction.     

A DFT based investigation into the electronic structure and properties of hydride rich rhodium clusters

Density functional theory has been used to investigate the structures, bonding and properties of a family of hydride rich late transition metal clusters of the type [Rh(6)(PH(3))(6)H(12)](x) (x = 0, +1, +2, +3 or +4), [Rh(6)(PH(3))(6)H(16)](x) (x = +1 or +2) and [Rh(6)(PH(3))(6)H(14)](x) (x = 0, +1 or +2). The positions of the hydrogen atoms around the pseudo-octahedral Rh(6) core in the optimized structures of [Rh(6)(PH(3))(6)H(12)](x) (x = 0, +1, +2, +3 or +4) varied depending on the overall charge on the cluster. The number of semi-bridging hydrides increased (semi-bridging hydrides have two different Rh-H bond distances) as the charge on the cluster increased and simultaneously the number of perfectly bridging hydrides (equidistant between two Rh centers) decreased. This distortion maximized the bonding between the hydrides and the metal centers and resulted in the stabilization of orbitals related to the 2T(2g) set in a perfectly octahedral cluster. In contrast, the optimized structures of the 16-hydride clusters [Rh(6)(PH(3))(6)H(12)](x) (x = +1 or +2) were similar and both clusters contained an interstitial hydride, along with one terminal hydride, ten bridging hydrides and two coordinated H(2) molecules which were bound to two rhodium centers in an eta(2):eta(1)-fashion. All the hydrides were on the outside of the Rh(6) core in the lowest energy structures of the 14-hydride clusters [Rh(6)(PH(3))(6)H(14)] and [Rh(6)(PH(3))(6)H(14)](+), which both contained eleven bridging hydrides, one terminal hydride and one coordinated H(2) molecule. Unfortunately, the precise structure of [Rh(6)(PH(3))(6)H(14)](2+) could not be determined as structures both with and without an interstitial hydride were of similar energy. The reaction energetics for the uptake and release of two molecule of H(2) by a cycle consisting of [Rh(6)(PH(3))(6)H(12)](2+), [Rh(6)(PH(3))(6)H(16)](2+), [Rh(6)(PH(3))(6)H(14)](+), [Rh(6)(PH(3))(6)H(12)](+) and [Rh(6)(PH(3))(6)H(14)](2+) were modelled, and, in general, good agreement was observed between experimental and theoretical results. The electronic reasons for selected steps in the cycle were investigated. The 12-hydride cluster [Rh(6)(PH(3))(6)H(12)](2+) readily picks up two molecules of H(2) to form [Rh(6)(PH(3))(6)H(16)](2+) because it has a small HOMO-LUMO gap (0.50 eV) and a degenerate pair of LUMO orbitals available for the uptake of four electrons (which are provided by two molecules of H(2)). The reverse process, the spontaneous release of a molecule of H(2) from [Rh(6)(PH(3))(6)H(16)](+) to form [Rh(6)(PH(3))(6)H(14)](+) occurs because the energy gap between the anti-bonding SOMO and the next highest energy occupied orbital in [Rh(6)(PH(3))(6)H(16)](+) is 0.9 eV, whereas in [Rh(6)(PH(3))(6)H(14)](+) the energy gap between the anti-bonding SOMO and the next highest energy occupied orbital is only 0.3 eV. At this stage the factors driving the conversion of [Rh(6)(PH(3))(6)H(14)](+) to [Rh(6)(PH(3))(6)H(12)](2+) are still unclear.