Subtle role of polyatomic anions in molecular construction: structures and properties of AgX bearing 2,4'-thiobis(pyridine) (X(-) = NO(3)(-), BF(4)(-), ClO(4)(-), PF(6)(-), CF(3)CO(2)(-), and CF(3)SO(3)(-))

Studies on the subtle effects and roles of polyatomic anions in the self-assembly of a series of AgX complexes with 2,4'-Py(2)S (X(-) = NO(3)(-), BF(4)(-), ClO(4)(-), PF(6)(-), CF(3)CO(2)(-), and CF(3)SO(3)(-); 2,4'-Py(2)S = 2,4'-thiobis(pyridine)) have been carried out. The formation of products appears to be primarily associated with a suitable combination of the skewed conformers of 2,4'-Py(2)S and a variety of coordination geometries of Ag(I) ions. The molecular construction via self-assembly is delicately dependent upon the nature of the anions. Coordinating anions afford the 1:1 adducts [Ag(2,4'-Py(2)S)X] (X(-) = NO(3)(-) and CF(3)CO(2)(-)), whereas noncoordinating anions form the 3:4 adducts [Ag(3)(2,4'-Py(2)S)(4)]X(3) (X(-) = ClO(4)(-) and PF(6)(-)). Each structure seems to be constructed by competition between pi-pi interactions of 2,4'-Py(2)S spacers vs Ag.X interactions. For ClO(4)(-) and PF(6)(-), an anion-free network consisting of linear Ag(I) and trigonal Ag(I) in a 1:2 ratio has been obtained whereas, for the coordinating anions NO(3)(-) and CF(3)CO(2)(-), an anion-bridged helix sheet and an anion-bridged cyclic dimer chain, respectively, have been assembled. For a moderately coordinating anion, CF(3)SO(3)(-), the 3:4 adduct [Ag(3)(2,4'-Py(2)S)(4)](CF(3)SO(3))(3) has been obtained similarly to the noncoordinating anions, but its structure is a double strand via both face-to-face (pi-pi) stackings and Ag.Ag interactions, in contrast to the noncoordinating anions. The anion exchanges of [Ag(3)(2,4'-Py(2)S)(4)]X(3) (X(-) = BF(4)(-), ClO(4)(-), and PF(6)(-)) with BF(4)(-), ClO(4)(-), and PF(6)(-) in aqueous media indicate that a [BF(4)(-)] analogue is isostructural with [Ag(3)(2,4'-Py(2)S)(4)]X(3) (X(-) = ClO(4)(-) and PF(6)(-)). Furthermore, the anion exchangeability for the noncoordinating anion compounds and the X-ray data for the coordinating anion compounds establish the coordinating order to be NO(3)(-) > CF(3)CO(2)(-) > CF(3)SO(3)(-) > PF(6)(-) > ClO(4)(-) > BF(4)(-).     

Oxygen evolution from BF3/MnO4-

MnO(4)(-) is activated by BF(3) to undergo intramolecular coupling of two oxo ligands to generate O(2). DFT calculations suggest that there should be a spin intercrossing between the singlet and triplet potential energy surfaces on going from the active intermediate [MnO(2)(OBF(3))(2)](-) to the O···O coupling transition state.     

Unsymmetrical linear pentanuclear nickel string complexes: [Ni(5)(tpda)(4)(H(2)O)(BF(4))](BF(4))(2) and [Ni(5)(tpda)(4)(SO(3)CF(3))(2)](SO(3)CF(3))

The one-electron oxidized linear pentanuclear nickel complexes [Ni(5)(tpda)(4)(H(2)O)(BF(4))](BF(4))(2) (1) and [Ni(5)(tpda)(4)(SO(3)CF(3))(2)](SO(3)CF(3)) (2) have been synthesized by reacting the neutral compound [Ni(5)(tpda)(4)Cl(2)] with the corresponding silver salts. These compounds have been characterized by various spectroscopic techniques. Compound 1 crystallizes in the monoclinic space group P2(1)/n with a = 15.3022(1) A, b = 31.0705(3) A, c = 15.8109(2) A, beta = 92.2425(4) degrees, V = 7511.49(13) A(3), Z = 4, and compound 2 crystallizes in the monoclinic space group C2/c with a = 42.1894(7) A, b = 17.0770(3) A, c = 21.2117(4) A, beta = 102.5688(8) degrees, V = 14916.1(5) A(3), Z = 8. X-ray structural studies reveal an unsymmetrical Ni(5) unit for both compounds 1 and 2. Compounds 1 and 2 show stronger Ni-Ni interactions as compared to those of the neutral compounds.     

Outer-Sphere Electron Transfer in Methylene Chloride: Concentration, Salt, and Temperature Dependences of the Oxidation of beta-Re(2)X(4)(cis-1,2-bis(diphenylphosphino)ethylene)(2) (X = Cl, Br) by [Co(dimethylglyoximate)(3)(BF)(2)]BF(4) and the Oxidation of Re(2)Br(4)(PMe(2)Ph)(4) by [Co(1,2-cyclohexanedione dioximate)(3)(BBu)(2)]BF(4)

The kinetics of the oxidation of beta-Re(2)X(4)(cis-1,2-bis(diphenylphosphino)ethylene)(2) (X = Cl, Br) by the cobalt clathrochelate [Co(dimethylglyoximate)(3)(BF)(2)]BF(4) and the oxidation of Re(2)Br(4)(PMe(2)Ph)(4) by the cobalt clathrochelate [Co(1,2-cyclohexanedione dioximate)(3)(BBu)(2)]BF(4) have been studied by the stopped-flow method as a function of temperature (-85 to -19 degrees C), added Bu(4)NBF(4) (0-0.100 M), and reactant concentration in the low dielectric solvent methylene chloride. For each reaction, approximately 100 different conditions were studied. The observed rate constants were well fit by a mechanism involving separate paths for free ion and the ion-paired Co(III) oxidant. The analysis yielded values for DeltaH() and DeltaS() for each path of each reaction and consistent DeltaH degrees and DeltaS degrees values for the ion-pairing of the cationic reactant and the electrolyte. In addition, temperature-dependent electrochemical measurements in 0.10 M Bu(4)NBF(4) yielded DeltaH degrees and DeltaS degrees for the electron transfer process. This is the first measurement of the homogeneous electron transfer reactivity of the dirhenium complexes, and they showed the expected high reactivity. The most notable result is a very high inhibition (ca. 700-fold) by added salt of only the [Co(dmg)(3)(BF)(2)]BF(4) reactions. We attribute this to a change of rate-controlling step, for the ion-paired path, to one involving anion migration. This appears only to occur when the magnitude of ion-pairing free energy is significantly greater than the magnitude of the free energy change for the electron transfer process.     

BF3-activated oxidation of alkanes by MnO4 -

The oxidation of alkanes and arylalkanes by KMnO(4) in CH(3)CN is greatly accelerated by the presence of just a few equivalents of BF(3), the reaction occurring readily at room temperature. Carbonyl compounds are the predominant products in the oxidation of secondary C-H bonds. Spectrophotometric and kinetics studies show that BF(3) forms an adduct with KMnO(4) in CH(3)CN, [BF(3).MnO(4)](-), which is the active species responsible for the oxidation of C-H bonds. The rate constant for the oxidation of toluene by [BF(3).MnO(4)](-) is over 7 orders of magnitude faster than by MnO(4)(-) alone. The kinetic isotope effects for the oxidation of cyclohexane, toluene, and ethylbenzene at 25.0 degrees C are as follows: k(C6H12)/k(C6D12) = 5.3 +/- 0.6, k(C7H8)/k(C7D8) = 6.8 +/- 0.5, k(C8H10)/k(C8D10) = 7.1 +/- 0.5. The rate-limiting step for all of these reactions is most likely hydrogen-atom transfer from the substrate to an oxo group of the adduct. A good linear correlation between log(rate constant) and C-H bond energies of the hydrocarbons is found. The accelerating effect of BF(3) on the oxidation of methane by MnO(4)(-) has been studied computationally by the Density Functional Theory (DFT) method. A significant decrease in the reaction barrier results from BF(3) coordination to MnO(4)(-). The BF(3) coordination increases the ability of the Mn metal center to achieve a d(1) Mn(VI) electron configuration in the transition state. Calculations also indicate that the species [2BF(3).MnO(4)](-) is more reactive than [BF(3).MnO(4)](-).     

Competition between NH.HIr Intramolecular Proton-Hydride Interactions and NH.FBF(3)(-) or NH.O Intermolecular Hydrogen Bonds Involving [IrH(2-thiazolidinethione)(4)(PCy(3))](BF(4))(2) and Related Complexes

The reaction of IrH(5)(PCy(3))(2) in acetone with 2 equiv of HBF(4) results in the formation of the air-stable complex [Ir(H)(2)(PCy(3))(2)(acetone)(2)]BF(4), 1. The reaction of 1 with an excess of 2-thiazolidinethione or 2-benzothiazolethione in the presence of 2 equiv of HBF(4) gives the complexes [Ir(H)(PCy(3))(L)(4)](BF(4))(2) (2a, L = 2-thiazolidinethione; 2b, L = 2-benzothiazolethione). Complex 2a has an intramolecular NH.H(Ir).HN interaction both in the crystalline solid as determined by X-ray diffraction and in a CD(2)Cl(2) solution as determined by the T(1) method. The d(HH) were determined to be 2.2 +/- 0.1 ? in the solid state and 1.9 +/- 0.1 ? in solution. The NH.H(Ir).HN interactions and NH.F.HN hydrogen bonds which involve FBF(3)(-) form a four-member ring in a butterfly conformation. The nOe effect of the hydride on the NH proton is around 10%. A crystal of 2a is in the triclinic space group P&onemacr; with a = 11.426(3), b = 11.922(3), c = 19.734(4) ?, alpha = 87.05(1) degrees, beta = 88.23(1) degrees, gamma = 75.50(1) degrees, V = 2599(1) ?(3), and Z = 2 at T = 173 K; full-matrix least-squares refinement on F(2) was performed for 10 198 independent reflections; R[F(2)>2sigma(F(2))] = 0.0480, R(w)(F(2)) = 0.099. The formation of the NH.HIr proton-hydride interaction is as favorable as the formation of intermolecular hydrogen bonds NH.FBF(3)(-) or NH.O hydrogen bonds with OPPh(3) or H(2)O in CD(2)Cl(2). A similar NH.HIr interaction also has been observed in the complexes [Ir(H)(2)(PCy(3))(2)(L)(2)]BF(4) (3a, L = 2-thiazolidinethione; 3b, L = 2-benzothiazolethione) but not in the complexes with L = NH(2)NH(2) (3c) and L = NH(3) (3d). Both the NH and IrH protons are deuterated when a solution of 2 or 3 in C(6)D(6) is exposed to 1 atm of D(2) gas or D(2)O.     

Oxidation of linear trinuclear ruthenium complexes [Ru(3)(dpa)(4)Cl(2)] and [Ru(3)(dpa)(4)(CN)(2)]: synthesis, structures, electrochemical and magnetic properties

The neutral, monocationic, and dicationic linear trinuclear ruthenium compounds [Ru(3)(dpa)(4)(CN)(2)], [Ru(3)(dpa)(4)(CN)(2)][BF(4)], [Ru(3)(dpa)(4)Cl(2)][BF(4)], and [Ru(3)(dpa)(4)Cl(2)][BF(4)](2) (dpa=the anion of dipyridylamine) have been synthesized and characterized by various spectroscopic techniques. Cyclic voltammetric and spectroelectrochemical studies on the neutral and oxidized compounds are reported. These compounds undergo three successive metal-centered one-electron-transfer processes. X-ray structural studies reveal a symmetrical Ru(3) unit for these compounds. While the metal--metal bond lengths change only slightly, the metal--axial ligand lengths exhibit a significant decrease upon oxidation of the neutral complex. The electronic configuration of the Ru(3) unit changes as the axial chloride ligands are replaced by the stronger "pi-acid" cyanide axial ligands. Magnetic measurements and (1)H NMR spectra indicate that [Ru(3)(dpa)(4)Cl(2)] and [Ru(3)(dpa)(4)Cl(2)][BF(4)](2) are in a spin state of S=0 and [Ru(3)(dpa)(4)Cl(2)][BF(4)], [Ru(3)(dpa)(4)(CN)(2)], and [Ru(3)(dpa)(4)(CN)(2)][BF(4)] are in spin states of S=1/2, 1, and 3/2, respectively. These results are consistent with molecular orbital (MO) calculations.     

A theoretical investigation of the interaction between small Pd particles and 1-butyl-3-methyl imidazolium ionic liquids with Cl(-), BF(4)(-) and PF(6)(-) anions

Density functional calculations have been used to investigate the interaction between Pd(n) clusters (n = 1-6) and 1-butyl-3-methylimidazolium (Bmim(+)) based ionic liquids (ILs) with the anions [Cl(-)], [BF(4)(-)] and [PF(6)(-)]. The interaction of small Pd(n) clusters (1 ≤ n ≤ 6) with a single cation or anion is also studied. The interaction strengths in anion-Pd(n) categories with n = 1-6 follow the trend [Cl(-)] > [BF(4)(-)] > [PF(6)(-)]. The cation could also form interactions with Pd(n) clusters. Compared with a single anion or cation, the interaction could be strengthened when palladium particles interact with the whole ion pair. Further studies indicated that anionPd interaction is the decisive factor in the interaction between the Pd atom and the whole ion pair. The Pd(2) dimer interacts with the whole ion pair much more strongly than the Pd atom. Solvent effects have been considered in the present study by means of the polarizable continuum model. It is found that the stability of [Bmim(+)·BF(4)(-)]-Pd(n) and [Bmim(+)·PF(6)(-)]-Pd(n) complexes with n = 1 and 2 can be improved in solvents.     

New monodentate amidine superbasic ligands with a single configuration in fac-[Re(CO)3(5,5'- or 6,6'-Me2bipyridine)(amidine)]BF4 complexes

Treatment of two precursors, fac-[Re(CO)(3)(L)(CH(3)CN)]BF(4) [L = 5,5'-dimethyl-2,2'-bipyridine (5,5'-Me(2)bipy) (1) and 6,6'-dimethyl-2,2'-bipyridine (6,6'-Me(2)bipy) (2)], with five C(2)-symmetrical saturated heterocyclic amines yielded 10 new amidine complexes, fac-[Re(CO)(3)(L)(HNC(CH(3))N(CH(2)CH(2))(2)Y)]BF(4) [Y = CH(2), (CH(2))(2), (CH(2))(3), NH, or O]. All 10 complexes possess the novel feature of having only one isomer (amidine E configuration), as established by crystallographic and (1)H NMR spectroscopic methods. We are confident that NMR signals of the other possible isomer (amidine Z configuration) would have been detected, if it were present. Isomers are readily detected in closely related amidine complexes because the double-bond character of the amidine C-N3 bond (N3 is bound to Re) leads to slow E to Z isomer interchange. The new fac-[Re(CO)(3)(L)(HNC(CH(3))N(CH(2)CH(2))(2)Y)]BF(4) complexes have C-N3 bonds with essentially identical double-bond character. However, the reason that the Z isomer is so unstable as to be undetectable in the new complexes is undoubtedly because of unfavorable clashes between the equatorial ligands and the bulky N(CH(2)CH(2))(2)Y ring moiety of the axial amidine ligand. The amidine formation reactions in acetonitrile (25 °C) proceeded more easily with 2 than with 1, indicating that the distortion in 6,6'-Me(2)bipy resulting from the proximity of the methyl substituents to the inner coordination sphere enhanced the reactivity of the coordinated CH(3)CN. Reaction times for 1 and 2 exhibited a similar dependence on the basicity and ring size of the heterocyclic amine reactants. Moreover, when the product of the reaction of 1 with piperidine, fac-[Re(CO)(3)(5,5'-Me(2)bipy)(HNC(CH(3))N(CH(2)CH(2))(2)CH(2))]BF(4), was challenged in acetonitrile-d(3) or CDCl(3) with a 5-fold excess of the strong 4-dimethylaminopyridine ligand, there was no evidence for replacement of the amidine ligand after two months, thus establishing that the piperidinylamidine ligand is a robust ligand. This chemistry offers promise as a suitable means for preparing isomerically pure conjugated fac-[(99m)Tc(CO)(3)L](n±) imaging agents, including conjugates with known bioactive heterocyclic amines.     

A high-pressure iron K-edge x-ray absorption spectral study of the spin-state crossover in (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))I(2) and (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))(BF(4))(2)

The room temperature iron K-edge X-ray absorption near edge structure spectra of (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))I(2) and (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))(BF(4))(2) have been measured between ambient and 88 and 94 kbar, respectively, in an opposed diamond anvil cell. The iron(II) in (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))I(2)undergoes the expected gradual spin-state crossover from the high-spin state to the low-spin state with increasing pressure. In contrast, the iron(II) in (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))(BF(4))(2) remains high-spin between ambient and 78 kbar and is only transformed to the low-spin state at an applied pressure of between 78 and 94 kbar. No visible change is observed in the preedge peak in the spectra of (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))I(2) with increasing pressure, whereas the preedge peak in the spectra of ((e[HC(3,5-(CH(3))(2)pz)(3)](2))(BF(4))(2) changes as expected for a high-spin to low-spin crossover with increasing pressure. The difference in the spin-state crossover behavior of these two complexes is likely related to the unusual behavior of (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))(BF(4))(2) upon cooling.     

Trans --> cis isomerization of trans-[(dppm)2Ru(H)(L)][BF4] (L = P(OR)3) complexes: preparation of cis-[(dppm)2Ru(eta2-H2)(L)][BF4]2

A series of new dicationic dihydrogen complexes of ruthenium of the type cis-[(dppm)(2)Ru(eta(2)-H(2))(L)][BF(4)](2) (dppm = Ph(2)PCH(2)PPh(2); L = P(OMe)(3), P(OEt)(3), PF(O(i)Pr)(2)) have been prepared by protonating the precursor hydride complexes cis-[(dppm)(2)Ru(H)(L)][BF(4)] (L = P(OMe)(3), P(OEt)(3), P(O(i)Pr)(3)) using HBF(4).Et(2)O. The cis-[(dppm)(2)Ru(H)(L)][BF(4)] complexes were obtained from the trans hydrides via an isomerization reaction that is acid-accelerated. This isomerization reaction gives mixtures of cis and trans hydride complexes, the ratios of which depend on the cone angles of the phosphite ligands: the greater the cone angle, the greater is the amount of the cis isomer. The eta(2)-H(2) ligand in the dihydrogen complexes is labile, and the loss of H(2) was found to be reversible. The protonation reactions of the starting hydrides with trans PMe(3) or PMe(2)Ph yield mixtures of the cis and the trans hydride complexes; further addition of the acid, however, give trans-[(dppm)(2)Ru(BF(4))Cl]. The roles of the bite angles of the dppm ligand as well as the steric and the electronic properties of the monodentate phosphorus ligands in this series of complexes are discussed. X-ray crystal structures of trans-[(dppm)(2)Ru(H)(P(OMe)(3))][BF(4)], cis-[(dppm)(2)Ru(H)(P(OMe)(3))][BF(4)], and cis-[(dppm)(2)Ru(H)(P(O(i)Pr)(3))][BF(4)] complexes have been determined.     

The use of BF(-)(4) as the supporting electrolyte anion in voltammetric studies on carbon electrodes-a cautionary note

BF(-)(4), a supporting electrolyte anion commonly employed in aprotic as well as protic solvents, is found to give an anodic peak at around +0.8 V vs. SCE on glassy carbon electrodes in dimethylformamide media. The voltammetric peak is influenced by the sweep-rate as well as the concentration of BF(-)(4). The electrode, when anodically polarized under these conditions, is also found to retard the charge-transfer rate of the ferricyanide/ferrocyanide redox system. Possible mechanisms for formation of a film on the electrode are discussed; possibilities are fluorination of carbon atoms on the electrode surface by reactions such as C(lattice) + BF(-)(4) --> (CF ... BF(3))(lattice) + e(-) or CH(lattice) + BF(-)(4) --> (CF ... BF(3))(lattice) + H(+) + 2e-. The analytical importance of considering the influence of BF(-)(4) and other fluoride species on carbon electrodes in the anodic region is emphasized.     

Coordination of BF(4)(-) to oxovanadium(V) complexes,evidenced by the redox potential of oxovanadium(IV/V) couples in CH(2)Cl(2)

The oxidation of oxovanadium(IV) complexes [LV(IV)O] (L = tetradentate Schiff-base ligands such as N,N'-ethylenebis(salicylideneaminate)(2-) (salen) and N,N'-2,2-dimethylpropylenebis(salicylideneaminate)(2-) (salpn)) to [LV(V)O](+), believed to be responsible for the voltammetric response near 0.6 V vs Ag/AgCl in CH(2)Cl(2) in the presence of tetrabutylammonium tetrafluoroborate as a supporting electrolyte, is in fact coupled to a homogeneous process where [LVO](+) coordinates BF(4)(-) to form a neutral complex formulated as [LVOBF(4)]. The formation constants for [VO(salen)BF(4)] and [VO(salpn)BF(4)] are evaluated to be K(salen)(-)(1) = 1.1 x 10(2) M(-)(1) and K(salpn)(-)(1) = 1.4 x 10 M(-)(1), respectively. Crystal structure of [VO(salen)BF(4)] reveals that one of the fluorine atoms in BF(4)(-) is so close to the vanadium(V) atom as to be practically bound in the solid state.     

Synthetic,structural and binding studies of the 4,6-dimethyldibenzothiophene complex [(eta(5)-C(5)Me(5))Ru(CO)(2)(eta(1)(S)-4,6-Me(2)DBT)]BF(4): toward an understanding of deep hydrodesulfurization

The synthesis of the first completely characterized transition-metal complex containing a sulfur-bound 4,6-dimethyldibenzothiophene (4,6-Me(2)DBT) ligand, [CpRu(CO)(2)(eta(1)(S)-4,6-Me(2)DBT)]BF(4) (1) (Cp = eta(5)-C(5)Me(5)), is reported. X-ray studies of 1 and its 4-methyldibenzothiophene and dibenzothiophene analogues, [CpRu(CO)(2)(eta(1)(S)-4-MeDBT)]BF(4) (2) and [CpRu(CO)(2)(eta(1)(S)-DBT)]BF(4) (3), show that the Ru-S bond distances increase in the order, 3 < 2 < 1. Equilibrium studies on the series of [CpRu(CO)(2)(eta(1)(S)-DBTh)](+) compounds, where DBTh = DBT, 4-MeDBT, 4,6-Me(2)DBT, and 2,8-Me(2)DBT, show that the relative binding strengths of the dibenzothiophene ligands increase in the order 4,6-Me(2)DBT (1) < 4-MeDBT (20.2(1)) < DBT (62.7(6)) < 2,8-Me(2)DBT (223(3)). These results are the first to quantify the steric effect of 4- and 6-methyl groups on the sulfur-coordinating ability of dibenzothiophenes to transition-metal centers. They are also consistent with the proposal that 4- and 6-methyl groups reduce the coordination of dibenzothiophenes to active metal sites on hydrodesulfurization catalysts, which could account for the slow rate of 4-MeDBT and 4,6-Me(2)DBT hydrodesulfurization in petroleum feedstocks.     

Chiral supramolecules: organometallic molecular loops made from enantiopure R-[cis-Rh2(C6H4PPh2)2(CH3CN)6](BF4)2

Two enantiopure molecular loops, RR-[cis-Rh2(C6H4PPh2)2(py)2O2C(CF2)(n)CO2]2 (1, n = 2 and 2, n = 3) have been made from the reaction in CH2Cl2 and CH3OH of the inherently chiral dirhodium compound, R-[cis-Rh2(C6H4PPh2)2(CH3CN)6](BF4)2, and HO2C(CF2)(n)CO2H in the presence of an excess of pyridine. Single-crystal structure analyses reveal that each of these compounds is composed of two R-cis-Rh2(C6H4PPh2)2(ax-py)2(2+) units, and two equatorial perfluorodicarboxylate linkers, which form a loop oligomer. The 1H, 19F, and 31P[1H] NMR spectra in CDCl3 and C5D5N indicate that only one type of highly symmetric species exists in each solution, which is consistent with the solid-state structures.     

First paramagnetic 4d transition-metal complex with a redox-active tetrathiafulvalene derivative, [Ru(salen)(PPh3)(TTF-CH=CH-Py)]BF4 [salen(2-) = N,N'-ethan-1,2-diylbis(salicylidenamine), PPh3 = triphenylphosphine, TTF-CH=CH-Py = 4-(2-tetrathiafulvalenylethenyl)pyridine

The first paramagnetic 4d transition-metal complex with a redox-active tetrathiafulvalene ligand has been synthesized. The preparation, X-ray structure, electrochemistry, and electron paramagnetic resonance measurements of [Ru(salen)(PPh3)(TTF-CH=CH-Py)](BF4) [1(BF4)] are reported. The crystal structure reveals that the paramagnetic Ru(III) (s = 1/2) center is in a tetragonally elongated octahedral geometry and the TTF-CH=CH-Py ligand is coordinated to the axial position of the Ru(III) ion through the nitrogen atom of the pyridine group. Thus, 1(BF4) is an attractive precursor to study future pi-4d interactions in dual-property conducting and magnetic materials.     

New BF(-)(4) and ClO(-)(4)-selective membrane electrodes and their pharmaceutical applications

The construction and general performance characteristics of ion-selective membrane electrodes sensitive to BF(-)(4) and ClO(-)(4) anions, respectively, are described. All electrodes show near-Nernstian responses in the range 10(-2) -10(-5)M. The selectivity of the electrodes to a number of organic and inorganic anions are reported. The electrodes are useful in the potentiometric determination of a few pharmaceutical preparations. The method is simple, rapid and does not require prior sample pre-treatment.     

Contribution to the analysis of the predissociated rovibronic structure of the symmetric isotopomers 16O3 and 18O3 of ozone near 10,400 cm-1): [3A2(3(2)(0)) <-- X1A1(0(0)(0))] and 3B2 <-- X1A1

The absorption spectrum of ozone was recorded at low temperatures (down to -135 degrees C) by high resolution Fourier transform spectrometry and intra cavity laser absorption spectroscopy (ICLAS) near 10,400 cm-1. A preliminary analysis of the rotational structure of the absorption spectra of 16O3 and 18O3 shows that this spectral region corresponds to a superposition of two different electronic transitions, one with a very broad rotational structure, showing for the first time the asymmetric stretching frequency mode nu3 of the electronic state 3A2, the other formed by a completely diffuse band, probably the 2(1)(0) band of a new transition due to the triplet electronic state 3B2. Predissociation effects induce large broadening of the rotational lines for the transition centered at 10,473 cm-1 identified as the 3(2)(0) band of the 3A2 <-- X1A1 electronic transition. The rotational structure cannot be analyzed directly but instead the band contour method was used to confirm the symmetry of the transition and to estimate the spectroscopic constants for the 16O isotopomer. The origin of the band is at 10,473 +/- 3 cm-1 and the value of the 16O3(3A2) antisymmetric stretching frequency mode is equal to 460 +/- 2 cm-1. We believe that the diffuse band is due to the 3B2 state and is located at about 10,363 +/- 3 cm-1 for 16O3 and 10,354 +/- 3 cm-1 for 18O3. The isotopic rules confirm the different results obtained for 18O3 and 16O3.     

Tris(chloranilato)ferrate(III) anionic building block containing the (Dihydroxo)oxodiiron(III) dimer cation: synthesis and characterization of [(TPA)(OH)FeIIIOFeIII(OH)(TPA)][Fe(CA)3]0.5(BF4)0.5.1.5MeOH.H2O [TPA = tris(2-pyridylmethyl)amine; CA = chloranilate

[(TPA)(OH)FeIIIOFeIII(OH)(TPA)][Fe(CA)3]0.5(BF4)0.5.1.5MeOH.H2O (1) which possesses both the [FeIII(CA)3]3- (CA= chloranilate) and hydroxooxoiron(III) ions has had its structure determined by single-crystal X-ray diffraction. The 2-300 K magnetic susceptibility of 1 provides the magnetic parameters, g = 2.07, J/kB = -165 K (115 cm-1), theta = -1 K, and the spin impurity, rho = 0.05, which indicates a strong antiferromagnetic interaction between iron(III) ions via the oxo anion.     

Small gas-phase dianions of Zn3O(4)(2-), Zn4O(5)(2-), CuZn2O(4)(2-), Si2GeO(6)(2-), Ti2O(5)(2-) and Ti3O(7)(2-)

We have searched for new species of small oxygen-containing gas-phase dianions produced in a secondary ion mass spectrometer by Cs+ ion bombardment of solid samples with simultaneous exposure of their surfaces to O2 gas. The targets were a pure zinc metal foil, a copper-contaminated zinc-based coin, two silicon-germanium samples (Si(1-x)Ge(x)(with x= 6.5% or 27%)) and a piece of titanium metal. The novel dianions Zn3O(4)(2-), Zn4O(5)(2-), CuZn2O(4)(2-), Si2GeO(6)(2-), Ti2O(5)(2-) and Ti3O(7)(2-) have been observed at half-integer m/z values in the negative ion mass spectra. The heptamer dianions Zn3O(4)(2-) and Ti2O(5)(2-) have been unambiguously identified by their isotopic abundances. Their flight times through the mass spectrometer are approximately 20 micros and approximately 17 micros, respectively. The geometrical structures of the two heptamer dianions Ti2O(5)(2-), and Zn3O(4)(2-) are investigated using ab initio methods, and the identified isomers are compared to those of the novel Ge2O(5)(2-) and the known Si2O(5)(2-) and Be3O(4)(2-) dianions.