Duward F. Shriver

Vibrational spectroscopy and structure of polymer electrolytes, poly(ethylene oxide) complexes of alkali metal salts

Abstract Complexes of poly(ethylene oxide) (PEO), with various alkali metal salts are known to exhibit ionic conductivities which exceed 10−5(Ωcm)−1 at moderate temperatures. We have employed IR and Raman spectroseopy to study well characterized samples of the following polymer-salt complexes: PEO·NaBr, PEO·NaI, PEO·NaSCN, PEO·NaBF4, PEO·NaCF3SO3, PEO·KSCN, PEO·RbSCN and PEO·CsSCN. Cation-dependent vibrational bands observed in the far IR and M-On symmetric stretching bands observed in the Raman support a cation-oxygen atom interaction, and indicate the polyether chain may wrap around the cations. In particular, NaX and KX complexes of PEO are believed to have a helical configuration for the polymer which differs from that of pure PEO. Some general rules are presented for polymer-salt complex formation.

Vibrational Spectroscopic Determination of Structure and Ion Pairing in Complexes of Poly(ethylene oxide) with Lithium Salts

A structural model for crystalline complexes of poly(ethylene oxide) (PEO) with various lithium salts is presented, based on vibrational spectroscopic studies; these complexes are known to exhibit ionic conductivities of > 10 -/sup 5/ (/OMEGA/-cm)-/sup 1/ at 100/sup 0/C. Cation-dependent vibrational bands observed in the Raman indicate that significant cation-oxygen atom interactions occur and suggest that the polyether chain may wrap around the lithium cations. Spectroscopic studies indicate extensive contact ion pairing occurs in the PEO*LiNO/sub 3/ complex, and this may contribute to the somewhat lower ionic conductivity of this complex as compared to other lithium salt complexes with similar structures but weaker cation-anion interactions. 27 refs.

Conformation and Ion‐Transport Models for the Structure and Ionic Conductivity in Complexes of Polyethers with Alkali Metal Salts

Two ion‐transport mechanisms are described for ion transport in polyether‐alkali metal salt complexes: an intrahelical jumping process along crystalline (helical) regions of the polymer, and a transport process in the amorphous regions which is dependent on formation of fourfold coordination sites via mutual motion of ether oxygens from two or more polymer chains. The intrahelical jumping process may exhibit Arrhenius behavior, while transport in the amorphous regions should behave like a configurational entropy dominated process, showing a temperature dependence like , where is the equilibrium glass transition temperature. For the highly crystalline poly(ethylene oxide) complexes, an Arrhenius behavior is observed to dominate, whereas for the amorphous polyether salt complexes the configurational entropy behavior is observed. Even for the highly crystalline complexes, however, amorphous regions separate the crystalline regions of the polymer, and segmental motion of the polymer chains is postulated to be crucial here as well. The models are consistent with the observed frequency‐dependent ionic conductivity, as well as spectroscopic, x‐ray, thermal, and physical characterization measurements. They provide a reasonable microscopic picture for ion motion and yield testable predictions concerning the dependence of the ionic conductivity on pressure, temperature, and crystallinity.

Complex formation and ionic conductivity of polyphosphazene solid electrolytes

Abstract The linear poly[(alkoxy)phosphazene], [NP(OC 2 H 4 OC 2 H 4 OCH 3 ) 2 ] n (MEEP), has been synthesized and investigated as a polymeric electrolyte host material. Amorphous solvent free polymersalt complexes formed with a variety of mono-, di-, and trivalent salts and exhibit high ionic conductivity. The conductivity varies with changes in the identify of the cation, the anion and the salt concentration. It also exhibits a non-Arrhenius temperature dependence. For alkali-metal salt complexes the cations and anions both contribute to the ionic conductivity. The complex (LiSO 3 CF 3 ) 0.25 ·MEEP exhibits a conductivity at room temperature which is 2.5 orders of magnitude greater that the corresponding poly(ethylene oxide) complex.

Structure and ion transport in polymer-salt complexes

Abstract Polymer electrolytes based on alkali metal complexes of polyethers and cross-linked polyethers have significant cation mobility, which appears to arise from large-amplitude motions of the polymer. High chain flexibility not only promotes ion transport but it also is important for the initial formation of polymer-salt complexes. Several new polymer electrolyte systems are discussed which contain flexible polymer backbones and high concentrations of polar groups.

The Octahedral M6Y8 And M6Y12 Clusters of Group 4 and 5 Transition Metals

Publisher Summary This chapter discusses the octahedral M6Y8 and M6Y12 clusters of group 4 and 5 transition metals. Octahedral clusters of the electropositive metals, groups 3 to 7, are stabilized by π-donor ligands such as halides, chalcogenides, and alkoxides, but the majority accessible to solution chemistry is the halide complexes. Dilution of the pyridine surface with coadsorbed thiolphenol, a noncoordinating moiety, reduces the amount of cluster adsorbed to the surface and the average number of triflate ligands displaced by surface pyridine. The number of triflate ligands remaining on the surface-bound cluster may be adjusted with the thiolphenol/mercaptopyridine ratio. The different coordination environments about the core in the resulting material have been identified with differential pulse voltammetry. Both the α- and β-nitrogens of the azide ligand bind the cations, whereas only the sulfur atoms of the thiocyanate groups coordinate to the alkali metals. In addition to cation bridges, water molecules connect the azide ligands of adjacent clusters via hydrogen bonding.

Basicity and reactivity of metal carbonyls

Metal carbonyls are for the most part low oxidation state species which are susceptible to attack by electron seeking reagents. Therefore, a significant fraction of the chemistry of metal carbonyls and metal carbonyl derivatives involves their reaction with Lewis acids and nucleophiies, and many important synthetic reactions are of this type. This chemistry gives a unique character to metal carbonyls and similar organometallics, because Werner-type complexes are more resistant to attack by electron seeking reagents owing to the positive oxidation state of the central metal. As shown in equation I, there are several simple types of reactions which a metal complex, ML,, may undergo with a Lewis acid. Each of these is discussed here, but the description is brief for metal basicity and for ligand abstraction, because the former is reviewed extensively elsewhere, and the latter area is relatively limited. Greater detail is given for the formation of CO ligand bridged adducts, a recently discovered area which is yielding interesting

The role of metal cluster interactions in the proton-induced reduction of CO. the crystal structures of [PPN]{HFe4(CO)12} and HFe4(CO)12(η-COCH3)

Abstract The isolation and crystal structure of the iron carbonyl complex [PPN]-[HFe4(CO)12C] (I) from the reaction of [PPN]2[Fe4(CO)13] and HSO3CF3 shows it to be a carbine complex. The possible role of the carbide species in the proton-induced reaction of CO is discussed. The structurally similar complex (μ-H)Fe4(CO)12(η2-COCH3) (II) has also been prepared and its crystal structure determined. Both I and II contain carbon atoms bonded to four irons in a butterfly arrangement. In both, the hydride bridges the two cm3 (metal connectivity of three) iron atoms.

Ion Transport in the Polymer Electrolytes Formed Between Poly(ethylene succinate) and Lithium Tetrafluoroborate

Solid electrolyte complexes of poly(ethylene succinate), PESc, and LiBF/sub 4/ were prepared by heating the salt with the molten polymer. The complexes were completely amorphous over the concentration range 1:1 to 3:1 polymer repeat units:metal cation. At salt concentrations above the 1:1 composition, a salt phase was present, an at salt concentrations less than 3:1, free crystalline polymer was observed. Within the 1:1 to 3:1 concentration range, increasing salt concentration was accompanied by decreasing conductivity, and increasing glass transition temperatures. This behavio is discussed in terms of free-volume theory, with dynamical corrections.

Rhodium(I) catalyzed decomposition of formic acid

Abstract Rh(C 6 H 4 PPh 2 )(PPh 3 ) 2 catalyzes the decomposition of formic acid to CO 2 and H 2 . The initial step is the oxidative addition of formic acid to produce the intermediate Rh(HCO 2 )(PPh 3 ) 3 , which probably is followed by β-hydride elimination, to produce CO 2 and RhH(PPh 3 ) 3 . The latter reacts with formic acid to produce H 2 and to reform Rh(HCO 2 )(PPh 3 ) 3 .