New developments and directions in the area of elastomers and rubberlike elasticity

There are number of important developments in the area of elastomeric polymers, including (i) network chains of controlled stiffness, (ii) model elastomers (including dangling-chain networks), (iii) fluorosiloxane elastomers, (iv) new thermoplastic elastomers, (v) other new elastomers, (v) bimodal network chain-length distributions, (vi) cross linking in solution or in a state of deformation, and (vii) gel collapse. Interesting elastomeric composites include those with (i) in-situ generated ceramic-like particles, (ii) ellipsoidal fillers, (iii) clay-like layered fillers, (iv) polyhedral oligomeric silsesquioxane (POSS) particles, (v) porous fillers, (vi) elastomeric domains modifying ceramics, and (vii) controlled interfaces. New characterization techniques are being developed for elastomers, and there have been new developments in elasticity theory and in elastomer processing. Some examples of societal aspects of relevance are (i) synthesis of elastomers in environmentally-friendly solvents, (ii) biosynthesis, (iii), recyclability, (iv) improved adhesion to tire cords, and (v) better barrier properties in anti-terrorism clothing. Educational topics include curriculum development, and mobile laboratories for elastomer experiments and demonstrations.     

N,N'-ethylenebis(pyridoxylideneiminato) and N,N'-ethylenebis(pyridoxylaminato): synthesis, characterization, potentiometric, spectroscopic, and DFT studies of their vanadium(IV) and vanadium(V) complexes

The Schiff base N,N'-ethylenebis(pyridoxylideneiminato) (H(2)pyr(2)en, 1) was synthesized by reaction of pyridoxal with ethylenediamine; reduction of H(2)pyr(2)en with NaBH(4) yielded the reduced Schiff base N,N'-ethylenebis(pyridoxylaminato) (H(2)Rpyr(2)en, 2); their crystal structures were determined by X-ray diffraction. The totally protonated forms of 1 and 2 correspond to H(6)L(4+), and all protonation constants were determined by pH-potentiometric and (1)H NMR titrations. Several vanadium(IV) and vanadium(V) complexes of these and other related ligands were prepared and characterized in solution and in the solid state. The X-ray crystal structure of [V(V)O(2)(HRpyr(2)en)] shows the metal in a distorted octahedral geometry, with the ligand coordinated through the N-amine and O-phenolato moieties, with one of the pyridine-N atoms protonated. Crystals of [(V(V)O(2))(2)(pyren)(2)].2 H(2)O were obtained from solutions containing H(2)pyr(2)en and oxovanadium(IV), where Hpyren is the "half" Schiff base of pyridoxal and ethylenediamine. The complexation of V(IV)O(2+) and V(V)O(2) (+) with H(2)pyr(2)en, H(2)Rpyr(2)en and pyridoxamine in aqueous solution were studied by pH-potentiometry, UV/Vis absorption spectrophotometry, as well as by EPR spectroscopy for the V(IV)O systems and (1)H and (51)V NMR spectroscopy for the V(V)O(2) systems. Very significant differences in the metal-binding abilities of the ligands were found. Both 1 and 2 act as tetradentate ligands. H(2)Rpyr(2)en is stable to hydrolysis and several isomers form in solution, namely cis-trans type complexes with V(IV)O, and alpha-cis- and beta-cis-type complexes with V(V)O(2). The pyridinium-N atoms of the pyridoxal rings do not take part in the coordination but are involved in acid-base reactions that affect the number, type, and relative amount of the isomers of the V(IV)O-H(2)Rpyr(2)en and V(V)O(2)-H(2)Rpyr(2)en complexes present in solution. DFT calculations were carried out and support the formation and identification of the isomers detected by EPR or NMR spectroscopy, and the strong equatorial and axial binding of the O-phenolato in V(IV)O and V(V)O(2) complexes. Moreover, the DFT calculations done for the [V(IV)O(H(2)Rpyr(2)en)] system indicate that for almost all complexes the presence of a sixth equatorial or axial H(2)O ligand leads to much more stable compounds.     

A feasibility study on the use of Li(4)V(3)O(8) as a high capacity cathode material for lithium-ion batteries

Li(4)V(3)O(8) materials have been prepared by chemical lithiation by Li(2)S of spherical Li(1.1)V(3)O(8) precursor materials obtained by a spray-drying technique. The over-lithiated vanadates were characterised physically by using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and electrochemically using galvanostatic charge-discharge and cyclic voltammetry measurements in both the half-cell (vs. Li metal) and full-cell (vs. graphite) systems. The Li(4)V(3)O(8) materials are stable in air for up to 5 h, with almost no capacity drop for the samples stored under air. However, prolonged exposure to air will severely change the composition of the Li(4)V(3)O(8) materials, resulting in both Li(1.1)V(3)O(8) and Li(2)CO(3). The electrochemical performance of these over-lithiated vanadates was found to be very sensitive to the conductive additive (carbon black) content in the cathode. When sufficient carbon black is added, the Li(4)V(3)O(8) cathode exhibits good cycling behaviour and excellent rate capabilities, matching those of the Li(1.1)V(3)O(8) precursor material, that is, retaining an average charge capacity of 205 mAh g(-1) at 2800 mA g(-1) (8C rate; 1C rate means full charge or discharge of a battery in one hour), when cycled in the potential range of 2.0-4.0 V versus Li metal. When applied in a non-optimised full cell system (vs. graphite), the Li(4)V(3)O(8) cathode showed promising cycling behaviour, retaining a charge capacity (Li(+) extraction) above 130 mAh g(-1) beyond 50 cycles, when cycled in the voltage range of 1.6-4.0 V, at a specific current of 117 mA g(-1) (C/3 rate).     

苯甲醛在离子液体中的电化学行为

应用线性扫描循环伏安法、方波循环伏安法和计时电量法测定苯甲醛在3种离子液体C4M IMBF4、C6M IMBF4和C8M IMBF4中的电化学行为.实验表明,在C4M IIVIBF4离子液体中苯甲醛于GC电极上的还原包含两个连续、不可逆单电子过程,对应的方波I~E曲线峰电位Ep为-1.39 V和-1.69 V,估算的扩散系数分别为D1=1.5×10-8cm2/s和D2=1.3×10-8cm2/s.而在C6M IMBF4和C8M IMBF4离子液体中,则苯甲醛于GC电极仅显示一个电流峰,这可能是因为C4M IMBF4的碱性较C6M IMBF4和C8M IMBF4弱的缘故;而电流的衰减时间亦依C4M IMBF4,C6M IMBF4,C8M IMBF4,次序增长,并会导致更慢的异相动力学过程.     

Synthesis of phthalide derivatives using nickel-catalyzed cyclization of o-haloesters with aldehydes

The reaction of o-bromobenzoate (1 b) with benzaldehyde (2 a) in the presence of [NiBr(2)(dppe)] (dppe=1,2-bis(diphenylphosphino)ethane) and zinc powder in THF (24 hours, reflux temperature), afforded 3-phenyl-3H-isobenzofuran-1-one (3 a) in an 86 % yield. Similarly, o-iodobenzoate reacts with 2 a to give 3 a, but in a lower yield (50 %). A series of substituted aromatic and aliphatic aldehydes (2 b, 4-MeC(6)H(4)CHO; 2 c, 4-MeOC(6)H(4)CHO; 2 d, 3-MeOC(6)H(4)CHO; 2 e, 2-MeOC(6)H(4)CHO; 2 f, 4-CNC(6)H(4)CHO; 2 g, 4-(Me)(3)CC(6)H(4)CHO; 2 h, 4-C(6)H(5)C(6)H(4)CHO; 2 i, 4-ClC(6)H(4)CHO; 2 j, 4-CF(3)C(6)H(4)CHO; 2 k, CH(3)(CH(2))(5)CHO; 2 l, CH(3)(CH(2))(2)CHO) also underwent cyclization with o-bromobenzoate (1 b) producing the corresponding phthalide derivatives in moderate to excellent yields and with high chemoselectivity. Like 1 b, methyl 2-bromo-4,5-dimethoxybenzoate (1 c) reacts with tolualdehyde (2 b) to give the corresponding substituted phthalide 3 m in a 71 % yield. The methodology can be further applied to the synthesis of six-membered lactones. The reaction of methyl 2-(2-bromophenyl)acetate (1 d) with benzaldehyde under similar reaction conditions afforded six-membered lactone 3 o in a 68 % yield. A possible catalytic mechanism for this cyclization is also proposed.     

New highly stable metallabenzenes via nucleophilic aromatic substitution reaction

Treatment of the ruthenabenzene [Ru{CHC(PPh(3))CHC(PPh(3))CH}Cl(2)(PPh(3))(2)]Cl (1) with excess 8-hydroxyquinoline in the presence of CH(3)COONa under air atmosphere produced the S(N)Ar product [(C(9) H(6)NO)Ru{CHC(PPh(3))CHC(PPh(3))C}(C(9)H(6)NO)(PPh(3))]Cl(2) (3). Ruthenabenzene 3 could be stable in the solution of weak alkali or weak acid. However, reaction of 3 with NaOH afforded a 7:1 mixture of ruthenabenzenes [(C(9)H(6)NO)Ru{CHC(PPh(3))CHCHC}(C(9)H(6)NO)(PPh(3))]Cl (4) and [(C(9)H(6)NO)Ru{CHCHCHC(PPh(3))C}(C(9)H(6)NO)(PPh(3))]Cl (5), presumably involving a P-C bond cleavage of the metallacycle. Complex 3 was also reactive to HCl, which results in a transformation of 3 to ruthenabenzene [Ru{CHC(PPh(3))CHC(PPh(3))C}Cl(2)(C(9)H(6)NO)(PPh(3))]Cl (6) in high yield. Thermal stability tests showed that ruthenabenzenes 4, 5, and 6 have remarkable thermal stability both in solid state and in solution under air atmosphere. Ruthenabenzenes 4 and 5 were found to be fluorescent in common solvents and have spectral behaviors comparable to those organic multicyclic compounds containing large π-extended systems.     

Dititanium-containing 19-tungstodiarsenate(III) [Ti2(OH)2As2W19O67(H2O)]8-: synthesis, structure, electrochemistry, and oxidation catalysis

The dititanium-containing 19-tungstodiarsenate(III) [Ti(2)(OH)(2)As(2)W(19)O(67)(H(2)O)](8-) (1) has been synthesized and characterized by IR, TGA, elemental analysis, electrochemistry, and catalytic studies. Single-crystal X-ray analysis was carried out on Cs(8)[Ti(2)(OH)(2)As(2)W(19)O(67)(H(2)O)].2CsCl.12H(2)O (Cs-1), which crystallizes in the monoclinic system, space group P2(1)/m, with a=12.7764(19), b=19.425(3), c=18.149(3) A, beta=110.234(3) degrees, and Z=2. Polyanion 1 comprises two (B-alpha-As(III)W(9)O(33)) Keggin moieties linked through an octahedral {WO(5)(H(2)O)} fragment and two unprecedented square-pyramidal {TiO(4)(OH)} groups, leading to a sandwich-type structure with nominal C(2v) symmetry. Synthesis of 1 was accomplished by reaction of TiOSO(4) and K(14)[As(2)W(19)O(67)(H(2)O)] in a 2:1 molar ratio in aqueous, acidic medium (pH 2). Polyanion 1 could also be isolated as a tetra-n-butyl ammonium (TBA) salt, {(n-C(4)H(9))(4)N}(5)H(3)[Ti(2)(OH)(2)As(2)W(19)O(67)(H(2)O)] (TBA-1). TBA-1 was studied by cyclic voltammetry in acetonitrile (MeCN) solutions containing 0.1 M LiClO(4) and compared with the results obtained with Cs-1 in aqueous media. In MeCN, the Ti(IV) and W(VI) waves could not be separated distinctly. An important adsorption phenomenon on the glassy carbon working electrode was encountered both in cyclic voltammetry and in controlled potential electrolysis and was confirmed by Electrochemical Quartz Crystal Microbalance (EQCM) studies on a carbon film. TBA-1, dissolved in MeCN, reacts with H(2)O(2) to give peroxo complexes stable enough for characterization by UV-visible spectroscopy, cyclic voltammetry, and EQCM. TBA-1 shows high catalytic activity (TOF=11.3 h(-1)) in cyclohexene oxidation with aqueous H(2)O(2) producing products typical of a heterolytic oxidation mechanism. The stability of TBA-1 under turnover conditions was confirmed by using IR, UV-visible spectroscopy as well as cyclic voltammetry.     

Ring currents as probes of the aromaticity of inorganic monocycles : P5-, As5-, S2N2, S3N3-, S4N3+, S4N42+, S5N5+, S42+ and Se42+

Current-density maps were calculated by the ipsocentric CTOCD-DZ/6-311G** (CTOCD-DZ=continuous transformation of origin of current density-diamagnetic zero) approach for three sets of inorganic monocycles: S(4) (2+), Se(4) (2+), S(2)N(2), P(5) (-) and As(5) (-) with 6 pi electrons; S(3)N(3) (-), S(4)N(3) (+) and S(4)N(4) (2+) with 10 pi electrons; and S(5)N(5) (+) with 14 pi electrons. Ipsocentric orbital analysis was used to partition the currents into contributions from small groups of active electrons and to interpret the contributions in terms of symmetry- and energy-based selection rules. All nine systems were found to support diatropic pi currents, reinforced by sigma circulations in P(5) (-), As(5) (-), S(3)N(3) (-), S(4)N(3) (+), S(4)N(4) (2+) and S(5)N(5) (+), but opposed by them in S(4) (2+), Se(4) (2+) and S(2)N(2). The opposition of pi and sigma effects in the four-membered rings is compatible with height profiles of calculated NICS (nucleus-independent chemical shifts).     

Convenient syntheses of fluorous aryl iodides and hypervalent iodine compounds: ArI(L)n reagents that are recoverable by simple liquid/liquid biphase workups,and applications in oxidations of hydroquinones

Iodinations of the ortho, meta, and para fluorous arenes (R(f8)CH(2)CH(2)CH(2))(2)C(6)H(4) (R(f8)=(CF(2))(7)CF(3)) with I(2)/H(5)IO(6) in AcOH/H(2)SO(4)/H(2)O give 3,4-(R(f8)CH(2)CH(2)CH(2))(2)C(6)H(3)I (5) and the analogous 2,4- (6) and 2,5- (7) isomers, respectively. Spectroscopic yields are >90 %, but 5 and 7 must be separated by chromatography from by-products (yields isolated: 70 %, 97 %, 61 %). Reaction of 1,3,5-(R(f8)CH(2)CH(2)CH(2))(3)C(6)H(3) with PhI(OAc)(2)/I(2) gives 2,4,6-(R(f8)CH(2)CH(2)CH(2))(3)C(6)H(2)I (8) on multigram scales in 97 % yield. The CF(3)C(6)F(11)/toluene partition coefficients of 5-8 (24 degrees C: 69.5:30.5 (5), 74.7:25.3 (6), 73.9:26.1 (7), 98.0:2.0 (8)) are lower than those of the precursors, but CF(3)C(6)F(11)/MeOH gives higher values (97.0:3.0 (5), 98.6:1.4 (6), 98.0:2.0 (7), >99.3:<0.3 (8)). Reactions of 5-8 with excess NaBO(3) in AcOH yield the corresponding ArI(OAc)(2) species 9-12 (9, 85 % as a 90:10 9/5 mixture; 10, 97 %; 11, 95 %; 12, 93 % as a 95:5 12/8 mixture). These rapidly oxidize 1,4-hydroquinones in MeOH. Subsequent additions of CF(3)C(6)F(11) give liquid biphase systems. Solvent removal from the CF(3)C(6)F(11) phases gives 5-8 in >99-98 % yields, and solvent removal from the MeOH phases gives the quinone products, normally in >99-95 % yields. The recovered compounds 5-8 are easily reoxidized to 9-12 and used again.     

Sequential separation of Cu(II)/Ni(II)/Fe(II) from strong-acidic pickling wastewater with a two-stage process based on a bi-pyridine chelating resin

A self-synthesized bi-pyridine chelating resin (PAPY) could separate Cu(II)/Ni(II)/Fe(II) sequentially from strong-acidic pickling wastewater by a two-stage pH-adjusted process, in which Cu(II), Ni(II), and Fe(II) were successively preferred by PAPY. In the first stage (pH 1.0), the separation factor of Cu(II) over Ni(II) reached 61.43 in Cu(II)-Ni(II)-Fe(II) systems. In the second stage (pH 2.0), the separation factor of Ni(II) over Fe(II) reached 92.82 in Ni(II)-Fe(II) systems. Emphasis was placed on the selective separation of Cu(II) and Ni(II) in the first-stage. The adsorption amounts of Cu(II) onto PAPY were 1.2 mmol/g in the first stage, while those of Ni(II) and Fe(II) were lower than 0.3 mmol/g. Cu(II) adsorption was hardly affected by Ni(II) with the presence of dense Fe(II), but Cu(II) inhibited Ni(II) adsorption strongly. Part of preloaded Ni(II) could be replaced by Cu(II) based on the replacement effect. Compared with the absence of Fe(II), dense Fe(II) could obviously enhance the separation of Cu(II)-Ni(II). More than 95.0% of Cu(II) could be removed in the former 240 BV (BV for bed volume of the adsorbent) in the fixed-bed adsorption column process with the flow rate of 2.5 BV/h. As proved by X-ray photoelectron spectrometry (XPS) and density functional theory (DFT) analyses, Cu(II) exerted a much stronger deprotonation and chelation ability toward PAPY than Ni(II) and Fe(II). Thus, the work shows a great potential in the separation and purification of heavy metal resources from strong-acidic pickling wastewaters.     

Effects of Y (Ⅲ) Ions on the Fluorescence Properties of Ce(Ⅲ) Ion and the Organic Ligands in the Complex

The enhancement effects of Y ( Ⅲ) ions on the fluorescence of Ce ( Ⅲ) in Ce ( Ⅲ)-Y ( Ⅲ)-PMMA (polymethylmethacrylate ) or Ce ( Ⅲ)-Y ( Ⅲ)-PVC (polyvinyl chloride ) complex systems were observed. The influence of Y ( Ⅲ) ions on the emission spectra of PMMA ligands in PMMA-Y ( Ⅲ) and the fluorescent enhance- ment of Y( Ⅲ) on Ce( Ⅲ) emission in PMMA-Ce-Y by Y( Ⅲ) ion were studied. It was also of interest to note that when Y ( Ⅲ) ions were added into PMMA and into bpy(bipyridine ), respectively, the emission spectrum of PMMA ligands was split into fine structure bands by Y ( Ⅲ), and the fluorescence intensities of bpy ligands in bpy-Y ( Ⅲ) complexes were considerably increased.     

Six IPR isomers of C90 fullerene captured as chlorides: carbon cage connectivities and chlorination patterns

Three C(90) fractions were isolated by multi-step HPLC from fullerene soot obtained from direct current (DC) arc discharge of undoped graphite rods. C(90) of each fraction was chlorinated with VCl(4) or SbCl(5) in ampoules at 290-310 °C, affording a series of C(90)Cl(n) compounds. Single-crystal X-ray crystallography with the use of synchrotron radiation resulted in structure elucidation of seven C(90)Cl(n) compounds containing six different isolated pentagon rule (IPR) C(90) cages (the number of the C(90) isomer is given in the parentheses): C(90)(46)Cl(32) (I), C(90)(34)Cl(32) (II), C(90)(35)Cl(24) (III), and C(90)(35)Cl(28) (IV), C(90)(32)Cl(24) (V as co-crystals with III), co-crystals of C(90)(30)Cl(22) and C(90)(28)Cl(24) (VI), and C(90)(28)Cl(24) (VII). Cage connectivities of C(90) isomers 35 and 28 have been crystallographically confirmed for the first time. The chlorination patterns of the C(90)Cl(n) molecules are discussed in terms of the formation of isolated aromatic systems and isolated C=C double bonds on the fullerene cage. The distribution of six C(90) isomers in three HPLC fractions is compared with data from the literature.     

Solid state NMR characterization of individual compounds and solid solutions formed in Sc(2)O(3)--V(2)O(5)--Nb(2)O(5)--Ta(2)O(5) system

In this study, (51)V, (45)Sc and (93)Nb MAS NMR combined with satellite transition spectroscopy analysis were used to characterize the complex solid mixtures: VNb(9(1-x))Ta(9x)O(25), ScNb((1-x))Ta(x)O(4) and ScNb(2(1-x))Ta(2x)VO(9) (x = 0, 0.3, 0.5, 0.7, 1.0). This led us to describe the structures of Sc and V sites. The conclusions were based on accurate values for (51)V quadrupole coupling and chemical shift tensors obtained with (51)V MAS NMR/SATRAS for VNb(9)O(25), VTa(9)O(25) and ScVO(4). The (45)Sc NMR parameters have been obtained for Sc(2)O(3), ScVO(4), ScNbO(4) and ScTaO(4). On the basis of (45)Sc NMR and data available from literature, the ranges of the (45)Sc chemical shift have been established for ScO(6) and ScO(8). The gradual change of the (45)Sc and (51)V NMR parameters with x confirms the formation of solid solutions in the process of synthesis of VNb(9(1-x))Ta(9x)O(25) and ScNb((1-x))Ta(x)O(4), in contrast to ScNb(2(1-x))Ta(2x)VO(9). The cation sublattice of ScNb((1-x))Ta(x)O(4) is found to be in octahedral coordination. The V sites in VNb(9(1-x))Ta(9x)O(25) are present in the form of slightly distorted tetrahedra. The (93)Nb NMR parameters have been obtained for VNb(9)O(25).     

Investigations on the coupling of ethylene and alkynes in [IrTp Me2] compounds: water as an effective trapping agent

The reaction of the bis(ethylene) complex [Tp(Me(2) )Ir(C(2)H(4))(2)] (1) (Tp(Me(2) ): hydrotris(3,5-dimethylpyrazolyl)borate) with two equivalents of dimethyl acetylenedicarboxylate (DMAD) in CH(2)Cl(2) at 25 degrees C gives the hydride-alkenyl species [Tp(Me(2) )IrH{C(R)=C(R)C(R)=C(R)CH=CH(2)}] (2, R: CO(2)Me) in high yield. A careful study of this system has established the active role of a number of intermediates en route to producing 2. The first of these is the iridium(I) complex [Tp(Me(2) )Ir(C(2)H(4))(DMAD)] (4) formed by substitution of one of the ethylene ligands in 1 by a molecule of DMAD. Complex 4 reacts further with another equivalent of the alkyne to give the unsaturated metallacyclopentadiene [Tp(Me(2) )Ir{C(R)=C(R)C(R)=C(R)}], which can be trapped by added water to give adduct 7, or can react with the C(2)H(4) present in solution generating complex 2. This last step has been shown to proceed by insertion of ethylene into one of the Ir--C bonds of the metallacyclopentadiene and subsequent beta-H elimination. Complex 1 reacts sequentially with one equivalent of DMAD and one equivalent of methyl propiolate (MP) in the presence of water, with regioselective formation of the nonsymmetric iridacyclopentadiene [Tp(Me(2) )Ir{C(R)=C(R)C(H)=C(R)}(H(2)O)] (9). Complex 9 reacts with ethylene giving a hydride-alkenyl complex 10, related to 2, in which the C(2)H(4) has inserted regiospecifically into the Ir--C(R) bond that bears the CH functionality. Heating solutions of either 2 or 10 in CH(2)Cl(2) allows the formation of the allyl species 3 or 11, respectively, by simple stereoselective migration of the hydride ligand to the Calpha alkenyl carbon atom and concomitant bond reorganization of the resulting organic chain. All the compounds described herein have been characterized by microanalysis, IR and NMR spectroscopy, and for the case of 3, 7, 7CO, 8NCMe, 9, 9NCMe, and 10, also by single-crystal X-ray diffraction studies.     

A challenge to chemical intuition: donor-acceptor interactions in H3B-L and H2B+-L (L=CO; EC5H5, E=N-Bi)

The equilibrium geometries and bond energies of the complexes H(3)B-L and H(2)B(+)-L (L=CO; EC(5)H(5): E=N, P, As, Sb, Bi) have been calculated at the BP86/TZ2P level of theory. The nature of the donor-acceptor bonds was investigated by energy decomposition analysis (EDA). The bond strengths of H(3)B-L have the order CO>N>P>As>Sb>Bi. The calculated values are between D(e)=37.1 kcal mol(-1) for H(3)B-CO and D(e)=6.9 kcal mol(-1) for H(3)B-BiC(5)H(5). The bond dissociation energies of the cations H(2)B(+)-CO and H(2)B(+)-EC(5)H(5) are larger than for H(3)B--L, particularly for complexes of the heterobenzene ligands. The calculated values are between D(e)=51.9 kcal mol(-1) for H(2)B(+)-CO and D(e)=122.1 kcal mol(-1) for H(2)B(+)-NC(5)H(5). The trend of the BDE of H(2)B(+)-CO and H(2)B(+)-EC(5)H(5) is N>P>As>Sb>Bi>CO. A surprising result is found for H(2)B(+)-CO, which has a significantly stronger and yet substantially longer bond than H(3)B-CO. The reason for the longer but stronger bond in H(2)B(+)-CO compared with that in H(3)B-CO comes mainly from the change in electrostatic attraction and pi bonding at shorter distances, which increases more in the neutral system than in the cation, and to a lesser extent from the deformation energy of the fragments. The H(2)B(+)<--NC(5)H(5) pi( perpendicular) donation plays an important role for the stronger interactions at shorter distances compared with those in H(3)B-NC(5)H(5). The attractive interaction in H(2)B(+)--CO further increases at bond lengths that are shorter than the equilibrium value, but this is compensated by the energy which is necessary to deform BH(2) (+) from its linear equilibrium geometry to the bent form in the complex. The EDA shows that the contributions of the orbital interactions to the donor-acceptor bonds are always larger than the classical electrostatic contributions, but the latter term plays an important role for the trend in bond strength. The largest contributions to the orbital interactions come from the sigma orbitals. The EDA calculations suggest that heterobenzene ligands may become moderately strong pi donors in complexes with strong Lewis acids, while CO is only a weak pi donor. The much stronger interaction energies in H(2)B(+)-EC(5)H(5) compared with those in H(3)B-EC(5)H(5) are caused by the significantly larger contribution of the pi(perpendicular) orbitals in H(2)B(+)-EC(5)H(5) and by the increase of the binding interactions of the sigma+pi( parallel) orbitals.     

Solubilizing sodium fluoride in acetonitrile: synthesis, molecular structure, and complexation behavior of bis(organostannyl)methyl-substituted crown ethers

The synthesis of the crown-ether-substituted bis(organostannyl)methanes Ph(3)SnCH(2)Sn(Ph(2))-CH(2)-[16]crown-5 (1) and Ph(2)ISnCH(2)Sn(I)(Ph)-CH(2)-[16]crown-5 (2) is reported. Both compounds have been characterized by elemental analyses, (1)H, (13)C, (19)F, and (119)Sn NMR spectroscopy, and in the case of compound 2 also by electrospray ionization mass spectrometry. Single-crystal X-ray diffraction analysis revealed for the aqua complex 2.H(2)O trigonal-bipyramidal-configured tin atoms with intramolecular Sn(1)-O(1) and Sn(2)-O(1W) distances of 2.555(2) and 2.440(3) A, respectively. The water molecule is trapped in a sandwich-like fashion between the crown ether oxygen atoms O(2) and O(4) and the Sn(2) atom. NMR spectroscopy unambiguously proved the ability of compound 2 in acetonitrile to overcome the high lattice energy of sodium fluoride and to complex the latter under charge separation.     

Coordination polymers based on [Cp*Fe(η5-P5)]: solid-state structure and MAS NMR studies

Slow diffusion reactions of the pentaphosphaferrocene [Cp*Fe(η(5)-P(5))] (Cp*=η(5)-C(5)Me(5) (1)) with CuX (X=Cl, Br, I) in different stoichiometric ratios and solvent mixtures result in the formation of one- and two-dimensional polymeric compounds 2-6 with molecular formula [{Cu(μ-X)}{Cp*Fe(μ(3),η(5):η(1):η(1)-P(5))}](n) (X=Cl (2a), I (2'c)), [{Cu(μ-I)}{Cp*Fe(μ(3),η(5):η(1):η(1)-P(5))}](n) (3), [{CuX}{Cp*Fe(μ(4),η(5):η(1):η(1):η(1)-P(5))}](n) (X=Cl (4a), Br (4b), I (4c), Br (4'b), I (4'c)), [{Cu(3)(μ-I)(2)(μ(3)-I)}{Cp*Fe(μ(5),η(5):η(1):η(1):η(1):η(1)-P(5))}](n) (5) and [{Cu(4)(μ-X)(4)(CH(3)CN)}{Cp*Fe(μ(7),η(5):η(2):η(1):η(1):η(1):η(1):η(1)-P(5))}](n) (X=Cl (6a), Br (6b)), respectively. The polymeric compounds have been characterised by single-crystal X-ray diffraction analyses and, for selected examples, by magic angle spinning (MAS) NMR spectroscopy. The solid-state structures demonstrate the versatile coordination modes of the cyclo-P(5) ligand of 1, extending from two to five coordinating phosphorus atoms in either σ or σ-and-π fashion. In compounds 2a, 2'c and 3, two phosphorus atoms of 1 coordinate to copper atoms in a 1,2 coordination mode (2a, 2'c) and an unprecedented 1,3 coordination mode (3) to form one-dimensional polymers. Compounds 4a-c, 4'b, 4'c and 5 represent two-dimensional coordination polymers. In compounds 4, three phosphorus atoms coordinate to copper atoms in a 1,2,4 coordination mode, whereas in 5 the cyclo-P(5) ligand binds in an unprecedented 1,2,3,4 coordination mode. The crystal structures of 6a,b display a tilted tube, in which all P atoms of the cyclo-P(5) ligand are coordinated to copper atoms in σ- and π-bonding modes.     

Rational synthetic tuning between itinerant antiferromagnetism and ferromagnetism in the complex boride series Sc2FeRu(5-n)RhnB2 (0<or=n<or=5)

Single crystals of the complex boride series Sc(2)FeRu(5-n)Rh(n)B(2) (n=1, 3, 4) were synthesized by arc-melting the elements in water-cooled copper crucibles under argon atmospheres and were chemically characterized by single-crystal XRD and EDX analyses. The new compounds are isotypic and crystallize in the tetragonal space group P4/mbm with Z=2, adopting a substitutional variant of the Ti(3)Co(5)B(2)-type structure. The magnetically active iron atoms are arranged in chains with intra- and interchain distances of about 3.02 and 6.60 A, respectively. Strong ferromagnetic interactions are observed for both Sc(2)FeRuRh(4)B(2) (64 valence electrons (VE), TC approximately 350 K, mu(a)=3.1 mu(B)) and Sc(2)FeRu(2)Rh(3)B(2) (63 VE, T(C) approximately 300 K, mu(a)=3.0 mu(B)), whereas antiferromagnetic interactions are found in the case of Sc(2)FeRu(4)RhB(2) (61 VE, T(N) approximately 10 K, mu(eff)=3.2): The magnetism of the entire Sc(2)FeRu(5-n)Rh(n)B(2) (0相似文献   

Synthesis and structure of new carborane-substituted cyclotriphosphazenes

The reactions of [N(3)P(3)Cl(6)] with one, two, or three equivalents of the difunctional 1,2-closo-carborane C(2)B(10)H(10)[CH(2)OH](2) and K(2)CO(3) in acetone have been investigated. These reactions led to the new spiro-closo-carboranylphosphazenes gem-[N(3)P(3)Cl(6-2n)[(OCH(2))(2)C(2)B(10)H(10)](n)] (n=1 (1), 2 (2)) and the first fully carborane-substituted phosphazene gem-[N(3)P(3)[(OCH(2))(2)C(2)B(10)H(10)](3)] (3). A bridged product, non-gem-[N(3)P(3)Cl(4)[(OCH(2))(2)C(2)B(10)H(10)]] (4), was also detected. The reaction of the well-known spiro derivatives [N(3)P(3)Cl(2)(O(2)C(12)H(8))(2)] and [N(3)P(3)Cl(4)(O(2)C(12)H(8))] with the same carborane-diol and K(2)CO(3) in acetone gave the new compounds gem-[N(3)P(3)(O(2)C(12)H(8))(3-n)[(OCH(2))(2)C(2)B(10)H(10)](n)] (n=1 (5) or 2 (6), respectively), without signs of intra- or intermolecularly bridged species. Upon treatment with NEt(3) in acetone, compound 5 was converted into the corresponding nido-carboranylphosphazene. However, the reaction of gem-[N(3)P(3)(O(2)C(12)H(8))(2)[(OCH(2))(2)C(2)B(10)H(10)]] (5) with NEt(3) in ethanol instead of acetone proceeded in a different manner to give the new compound (NHEt(3))(2)[N(3)P(3)(O(2)C(12)H(8))(2)(O)[OCH(2)C(2)B(9)H(10)CH(2)OCH(2)CH(3)]] (7). For compounds with two 2,2'-dioxybiphenyl units, gem-[N(3)P(3)(O(2)C(12)H(8))(2)[(OCH(2))(2)C(2)B(10)H(10)]] (5), (NHEt(3))[N(3)P(3)(O(2)C(12)H(8))(2)[(OCH(2))(2)C(2)B(9)H(10)]] (8), and (NHEt(3))(2)[N(3)P(3)(O(2)C(12)H(8))(2)(O)[OCH(2)C(2)B(9)H(10)CH(2)OCH(2)CH(3)]] (7), a mixture of different stereoisomers may be expected. However, for 5 and 7 only the meso compounds seem to be formed, with the same (R,S)-configuration as in the precursor [N(3)P(3)Cl(2)(O(2)C(12)H(8))(2)]. The reaction of 5 to give 8 seems to proceed with a change of configuration at one phosphorus center, giving a racemic mixture. The crystal structures of the nido-carboranylphosphazenes 7 and 8 have been confirmed by X-ray diffraction methods.     

Coordination chemistry of the soluble metal oxide analogue [Mo5O13(OCH3)4(NO)]3- with manganese carbonyl species

The reactions of neutral or cationic manganese carbonyl species towards the oxo-nitrosyl complex [Na(MeOH)[Mo(5)O(13)(OCH(3))(4)(NO)]](2-) have been investigated in various conditions. This system provides an unique opportunity for probing the basic reactions involved in the preparation of solid oxide-supported heterogeneous catalysts, that is, mobility of transition-metal species at the surface and dissolution-precipitation of the support. Under nitrogen and in the dark, the reaction of in situ generated fac-[Mn(CO)(3)](+) species with (nBu(4)N)(2)[Na(MeOH)-[Mo(5)O(13)(OMe)(4)(NO)]] in MeOH yields (nBu(4)N)(2)[Mn(CO)(3)(H(2)O)[Mo(5)O(13)(OMe)(4)(NO)]] at room temperature, while (nBu(4)N)(3)[Na[Mo(5)O(13)(OMe)(4)(NO)](2)[Mn(CO)(3)](2)] is obtained under reflux. The former transforms into the latter under reflux in methanol in the presence of sodium bromide; this involves the migration of the fac-[Mn(CO)(3)](+) moiety from a basal kappa(2)O coordination site to a lateral kappa(3)O site. Oxidation and decarbonylation of manganese carbonyl species as well as degradation of the oxonitrosyl starting material and reaggregation of oxo(methoxo)molybdenum fragments occur in non-deareated MeOH, and both (nBu(4)N)(4)[Mn(H(2)O)(2)[Mo(5)O(16)(OMe)(2)](2)[Mn(CO)(3)](2)] and (nBu(4)N)(4)[Mn(H(2)O)(2)[Mo(5)O(13)(OMe)(4)(NO)](2)] as well as (nBu(4)N)(2)[MnBr[Mo(5)O(13)(OMe)(4)(NO)]] have been obtained in this way. The rhenium analogue (nBu(4)N)(2)[Re(CO)(3)(H(2)O)[Mo(5)O(13)(OMe)(4)(NO)]] has also been synthesized. The crystal structures of (nBu(4)N)(2)[Re(CO)(3)(H(2)O)[Mo(5)O(13)(OMe)(4)(NO)]], (nBu(4)N)(3)[Na[Mo(5)O(13)(OMe)(4)(NO)](2)[Mn(CO)(3)](2)], (nBu(4)N)(4)[Mn(H(2)O)(2)[Mo(5)O(16)(OMe)(2)](2)[Mn(CO)(3)](2)], (nBu(4)N)(4)[Mn(H(2)O)(2)[Mo(5)O(13)(OMe)(4)(NO)](2)] and (nBu(4)N)(2)[MnBr[Mo(5)O(13)(OMe)(4)(NO)]] have been determined.