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Infra-red investigations have been conducted on a sulphonated ethylene propylene diene monomer system (sulpho EPDM) wherein the sulphonate is neutralized with various monovalent and divalent cations. Analysis of these systems was conducted on thin polymer films which were also analysed in spectra from which the unfunctionalized EPDM contribution was subtracted. These studies have revealed that the interaction of cation and sulphonated polymer differs for each cation, and some conclusions have been drawn regarding the symmetry of the cation-sulphonate complex. Surprisingly, the functionalization process induces ordering of the methylene groups in a trans fashion in the solid ionomer. The degree of ordering depends on the specific cation suggesting, for the first time with these polymers, that the ionic aggregation induces an ordered rearrangement of the polymer chains. The ordering in these systems disappears after prolonged heating, suggesting that thermal relaxation of the ionic aggregate destroys the order in the polymer chains.

The bicyclo[3.2.1]octa-3,6-dien-2-yl anion (I), the anion I lithium cation complex, the allyl anion (X), the allylradical, the allyl anion lithium cation complex, the ethene molecule, and the ethene lithium cation complex have been studiedby means of multiconfigurational SCF (MCSCF) and analytical gradients. The calculations have been confined to minimaland split-valence basis sets. The large distance between the C2 olefinic bridge and the C3 carbanionic bridge of anion I andthe short C6-C7 bond distance imply bishomoaromaticity to be negligible. According to these results, homoaromaticity isnot responsible for the observed stability in many potentially homoaromatic carbanions. The stability of anion I in the gasphase is instead explained in terms of a simple electrostatic model, where the quadrupole moment in the C2 olefinic bridgestabilizes the charge in the C, carbanionic bridge. This model agrees quantitatively with experiment. Calculations on theanion I lithium cation complex showed that in solution an additional attractive interaction between the C2 olefinic bridge andthe lithium cation can contribute. This additional interaction is estimated to stabilize the carbanion-lithium ion pair in thegas phase by about 16 kcal/mol. However, the stabilizing interactions of anion I in solution (quadrupole-charge andcounterion-anion interactions) will be reduced by solvent shielding. The relative ratios of the different stabilizing interactionsare therefore difficult to estimate. The geometrical findings of this paper have been verified by a recent X-ray experiment.

A novel cyclophane consisting of diphenylamine and piperazine skeletons was synthesized by their direct 2:2 condensation using benzene as a template. The cyclophane was a very effective ligand for alkaline metal and ammonium cations, and showed highly selective extractability for lithium cation.

Classical methods extensively used for the synthesis of inorganic condensed phosphates are known to give compounds that are intermediate between inorganic and organic. We prepared the title compound to examine the possibility of using, in this new field, the ion exchange resin method. The cyclotetraphosphate is the first condensed phosphate associated with the ethylenediammonium ion and mixed monovalent cations. We describe its chemical preparation and crystal structure. The orthorhombic unit cell has the following dimensions: a = 13.135(3) A, b = 7.737(2) A, c = 15.478(4) A, V = 1573(2)A 3 , D m = 2.020 g/cm 3 , D x = 1.951 g/cm 3 , μ = 0.297 mm −1 , space group is Pcca with Z = 4. The crystal structure has been solved by using 2005 unique reflections with a final R value of 0.043 ( R w = 0.045). The principal feature of this compound lies in its linear atomic arrangement of the monovalent cations with different coordination polyhedra. The lithium cation is statistically distributed on two general positions with 0.5 occupancy, or moves very rapidly between these two positions. The P 4 O 4− 12 ring anion is located around the twofold axis. The cohesiveness and the stability of the crystal result from two kinds of weak hydrogen bonds: NH---O and O(W)H---O. The structure of this compound is compared to that of Na 2 [NH 3 (CH 2 ) 2 NH 3 ]P 4 O 12 .2H 2 O; half the sodium positions are occupied by lithium cations.

The high bonding power of lithium toward oxygen is indicated by the absorption frequency for the carbonyl bridged ion pair Li[η 5 -C 5 H 5 )Fe(CO) 2 ] and by the relative concentration of this species in THF solutions of this salt. Li[(η 5 -C 5 H 5 )Fe(CO) 2 ] is much more reactive towards epoxides than is the corresponding sodium salt, and this difference may be attributed to more effective coordination of epoxide oxygen by lithium cation.

Interactions between a Li + cation and the bases NH 3 and OH 2 are studied by ab initio molecular orbital methods. Basis sets range in size from 6-31G* to 6-311 + G** and include also double-valence types containing two sets of polarization functions. Interactions energies computed with the singly polarized (SP) sets are too high, due in large part to overestimates of the dipole moments of the bases. Both of these errors are greatly reduced when d functions are added to first-now atoms (DP). The contributions of electron correlation to the interactions are included via Moller-Plesset theory to second and third orders. Whereas the SP basis sets lead incorrectly to attractive contributions of correlation, this component is positive with the DP sets which, moreover, involve substantially smaller basis set superposition errors at both the SCF and correlated levels. The second set of d functions is responsible also for correct behavior of both the second- and third-order components of correlation. Lithium cation and proton affinities calculated with the DP basis set are in excellent accord with values measured experimentally.

The FOGO method is used to calculate proton affinities and lithium cation affinities. The molecules of primary interest in this study are the methyl-substituted amines. In addition, the lithium cation affinity of HF, H2O, CH3OH, H2CO, and HCN are calculated for comparison. Geometries of all species are fully optimized with a double-zeta (DZ) basis set, including polarization on hydrogen and the first-row elements by floating orbitals. Comparison with experimental values demonstrates that structural data and proton affinities resulting from this type of ab initio calculation are of chemical accuracy. The lithium cation affinities are also reasonably well reproduced, but the small experimental differences are not within the accuracy, which can be expected from this type of calculation.

LiClO4-organic solvent-nitroxide radical systems were studied using 2,2,6,6-tetramethylpiperidine nitroxide radical (TMPN). The Li+-TMPN interaction was observed by means of the 7Li NMR contact shift and the paramagnetic broadening of the 7Li NMR signal. The effects were found to be solvent dependent and were interpreted with donor and acceptor numbers of solvents. The quantitative analysis of the data was done and the formation constants, the life times and the 7Li hyperfine splitting constants of the Li+-TMPN complexes were determined. The 7Li NMR results and the former EPR results were compared.

By the methods of classical and oscillographic polarography, electrolysis with controlled potential and spectrophotometry, the mechanism of electrochemical generation and the active centers nature of anionic polymerization of methyl methacrylate in dimethylformamide was investigated. It was shown that in dimethylformamide in the presence of tetraalkylammonium cations, methyl methacrylate carbanions exist as solvately divided ion pairs in which the electrostatic interaction is determined by the radius of the cation. It affects the chemical stages rate of the electrochemical generation of carbanions and appears by the anomalous shift of ζ 1/2 of polarographic reduction with the increasing of the cation radius of the supporting electrolyte. The replacement of the lithium cation with tetraalkylammonium changes the interaction type of methyl methacrylate carbanion with the counterion.

The distributions of lithium cation, picrate anion and dibenzo-14-crown-4 (DB14C4) and its analogs between water and various solvents, as well as the formation of ion pairs of lithium picrate and crown in these solvents, were studied spectrophotometrically at 24 ± 1 °C. The solvents used included benzene, chloroform, dichloromethane, 1,2-dichloroethane, nitromethane, and nitrobenzene. A 1:1 complex cation was formed between Li + and crown among these solvents. Three different kinds of ion pairs of Li + -crown complex cation and picrate anion could be determined from a series of absorption maximum shifts. The effects of substituent groups on DB14C4 and solvents upon the extraction constant are presented. A plausible extraction mechanism is also suggested.

Electron correlation corrections have a considerable influence on the relative stabilities of lithium isocyanide (1), lithium cyanide (2), and the bridged form, 3. While Hartree-Fock theory finds 1 to be most stable and 3 not to be a minimum, MP2/6-31G* optimization indicates 3 to be the global minimum. At higher levels employing full fourth-order Moller-Plesset theory and a quadruply split valence and polarized basis set (MP4STDQ/6-311+G*), 2 is only about 2 kcal/mol less stable than 1 and 3, which are indicated to have nearly the same energy. LiNC thus is similar to C(Na)N and C(K)N, both of which are known to prefer T-shaped (bridged) structures in the gas phase. However, to an even greater extent than formerly realized, rotation of the lithium cation around the cyanide anion nucleus should be practically free. ΔH (LiCN) = 32.8 kcal/mol is estimated from the calculated lithium cation affinity of 151.2 kcal/mol. In addition, we find at the MP4SDTQ/6-31+G*//MP2/6-31G* level that the bridged form of NaCN is favored by 2–3 kcal/mol over the corresponding linear forms, which have nearly the same energy.

The carbonation reaction of type 1 sulforide anions allowed to synthetize both diastereoisomers of the corresponding sulfinyl esters according to the kinetic or thermodynamic control of the process. Furthermore the stereochemistry of this reaction was shown to be dependent of the amount of lithium salts present in the methylithium used as a base : 90% of asymmetric induction was actually observed under kinetic control by using a low content in lithium salts base, a result consistent with an electrophilic assistance of the lithium cation.

The method to study the mechanism of actinides (III) and lanthanides (III) liquid-liquid amine extraction from chloride media has been suggested. The technique is based on the determination of distribution coefficients for extraction of these elements from mixed salting-out agent solutions with common anion. Distribution coefficients were found to be independent of mean ion activity of lithium cation at constant water activity, when extraction of trace amounts of Eu (III) and Cm(III) by tri-n-octylammonium hydrochloride from mixed LiCl−CaCl2 solutions occurred. It has been concluded that lithium cation does not enter into the complexed extracted.

Photoresponsive cyclobutane-1,2-dicarbonyl-capped 2·n diazacrown ethers (7) have been prepared by intramolecular [2 + 2]photocycloaddition of p,p′-trimethylenedicinnamoyl-capped 2·n diazacrown ethers (5); the cyclobutane-1,2-dicarbonyl-capped 2.1 diazacrown ether (7a) showed a highly selective complexing ability for the lithium cation, although (5) did not show any complexing abilities for alkali, alkaline-earth, and other metal ions. The crystal structures of (5a), the 1 : 1 lithium and mercury(II) thiocyanate complexes (8) and (9) of (7a) have been determined by X-ray analyses. The structures of (8) and (9) revealed that the configuration of the cyclobutane ring is in the β-form and slightly distorted. Complex (8) consists of dimeric molecules in which the lithium atom is directly bonded to the two oxygen atoms of the amido groups and the two nitrogen atoms of the thiocyanate group of the counter anion and adjacent complex in a slightly distorted tetrahedral configuration. The Hg atom in (9) is also bonded directly to the two oxygen atoms of the amido groups, the two sulphur atoms of the thiocyanate groups, and the simple nitrogen atom of the counter anion of the adjacent complex in a distorted trigonal bipyramidal configuration.

Interaction energies of a proton and lithium cation with NH 3 , OH 2 , and HF axe computed at the SCF and Moller-Plesset levels. It is found that the basis set superposition errors at all levels with the 6-3 1G** basis set may be greatly reduced by including an additional diffuse sp shell on first-row atoms; the exponent of this shell has been optimized to 0.1.

1. Phosphorus-containing monopodands with short polyether chains between the terminal phosphoryl groups are effective complexing agents with respect to the lithium cation. 2. Phosphorus-containing mono- and tripodands of high coordination capacity form fairly stable complexes with the whole series of alkali metals, the stability of the complexes in the case of the ligands with flexible glycol fragments being higher than that in the case of the ligands with rigid pyrocatechol fragments.

A new polarographic method to study complex formation has been applied to the anodic waves of halide ions in acetonitrile. The formation of complexes, such as (Li+)2Cl−, (HR)2Cl− (HR = p-bromophenol), (Li+)(HR)Cl−, (Li+)2(HA)Cl− (HA = benzoic acid) was clarified.

A statistical treatment within the uniform electron gas model is employed to compute adiabatic interaction energies between alkali ions and heavy rare-gas atoms. An effective potential form is put forward for the treatment of induced distortion contributions to the interaction and a physically intuitive way is suggested to evaluate it for each specific partner.The results for heavy ions are in good agreement both with experiments and with previously computed curves. Deeper potential wells are found for the Lithium cation interacting wirh Ar, Kr, Ne and Xe whereas the correct behaviour is exhibited by the repulsive regions and by the attractive tails of their interactions.The rapidity and efficiency of the present modal in computing ion-neutral potential curves is pointed out and its feasibility for evaluating transport cross sections for gas mixtures containing ions is discussed.For this purpose, an extensive tabulation of such potentials is presented for Li, Na and K ions interacting with Ne, Ar, Kr and Xe neutral atoms.

Dilithium carbamyl phosphate, an antisickling agent, dissociates into lithium cations and carbamyl phosphate dianions in solution. In order to determine which ion is primarily responsible for the toxicity observed at very high doses of dilithium carbamyl phosphate, two groups of 15 mice each were given similar amounts of lithium in twice-daily ip injections for 21, 23, or 30 days. Six of the fifteen mice survived in group A (lithium chloride, 12.9 mEq of Li + /kg/day), and 8 of 15 mice survived in group B (dilithium carbamyl phosphate, 13.8 mEq of Li + /kg/day). Blood lithium concentrations measured 4–6 hr after an injection averaged 1.7 (±0.7 SD) mEq/liter for each group. Lithium concentrations were measured in 39 samples of tissue or tissue contents from mice in each group. In the surviving animals, lithium ranged from an average of 0.8 – 1.1 mEq/kg in liver to 5–15 mEq/kg in the contents of the lower intestinal tract. Lithium concentrations greater than 15 mEq/kg were often found in the tissues of the nonsurvivors. Hemoglobin carbamylation was 1.0 (±0.3 SD) mol of valine hydantoin/mol of hemoglobin tetramer in mice given dilithium carbamyl phosphate for 21–30 days. This study demonstrates that the toxic effects associated with administration of dilithium carbamyl phosphate appear to be due to the lithium cation rather than the carbamyl phosphate dianion. In all parameters measured, the toxic effects of lithium chloride paralleled those observed when an equivalent amount of lithium was administered as dilithium carbamyl phosphate.

In some instances, the electrodeposition of metals onto electrodes may involve the prior generation of solvated metal atoms in the region of the outer Helmholtz plane. As a consequence, recently developed spectroscopic methods for detecting species in the interfacial region may be used to observe the solvated metal atoms. Therefore, with this paper we initiate an investigation of the nature of the possible states of solvation for these species in order to try to predict parameters which would be critical to their identification. In this paper we estimate the frequency at the band maximum for the far infrared-active vibrations which we predict to exist for the solvated lithium atom. We argue that the forces of repulsion may be nearly the same for the cation and atom. Thus, by means of a comparison to the Morse potential, we identify parameters for that potential. We determine the magnitude of the force constant for the vibrations of the atom in its cage of solvent. We suggest that the vibrational maximum for the solvated lithium atom may lie in the range of 300–400 cm−1. In addition, we have used an INDO calculation to examine the interaction between several solvent molecules and the lithium cation and atom. Although the INDO calculation is known not to yield accurate values for the vibrational force constants, we find nevertheless that a comparison of calculations for the cation and atom suggest that the solvated atomic frequency ought to lie only slightly below that of the solvated cation. This trend agrees with our prediction which is based on the use of a model potential energy function.

Association constants between 1,4-benzoquinone radical anion and lithium cation in organic solvents have been estimated by studying the variation in the polarographic half-wave potential for the reduction of 1,4-benzoquinone with solution composition. The ion pairs of contact type were identified in acetonitrile, propylene carbonate, dimethylformamide, dimethylacetamide, dimethylsulphoxide and diethylformamide using uv-vis spectrophotometry and esr technique. The association constant was observed to decrease with increase in the Lewis basicity of a solvent. It is shown that the logarithm of the association constant is a linear function of Gutmann's donicity; consequently the variation in association constant is discussed in terms of solvation of the cation. Structural aspects of the ionic interaction were computed according to the restricted LHP method in the π-approximation.

Es wird versucht, die unterschiedlichen Einflusse von Zusatzsubstanzen bei der mit Lithiumalkylkatalysatoren initiierten Copolymerisation von Styrol und α-Methylstyrol theoretisch zu erklaren. Die Hauptrolle spielt dabei das durch Donatoren solvatisierte Lithiumkation, das in Wechselwirkung mit den Monomeren Styrol und α-Methylstyrol tritt. An attempt is made to explain the effect of different additives on the lithium catalyzed polymerization of styrene and α-methylstyrene. The reaction appears to be determined by the lithium cation solvatized by electron donors and its interaction with styrene and α-methylstyrene.

The i.r. spectrum of ordered spinels LiXIIIYIII4O8(XIII = Ga, Fe, In; YIII = Cr, Rh) are discussed and assigned with the help of 6Li-7Li isotopio shifts. Two bands only may be assigned to definite motions of specific cations or coordinated groups: one band in the 450–350 cm−1 region exhibits an important 6Li-7Li isotopic shift and is assigned to a displacement of the lithium cation. The lowest-lying frequency strongly depends on the mass of the XIII tetrahedral cation and thus is assigned to a translation of this cation. All the remaining bands, in the 700–500 cm−1 region, are related to mixed vibrations involving the simultaneous participation of XIII and YIII cations. These assignments completely disagree with those of DeAngelis et al., which are shown to rely upon erroneous considerations. The disordered phase of LiGaCr4O8 (statistical distribution of Li and Ga cations on tetrahedral sites) has also been investigated and the main features of its i.r. spectrum are briefly discussed.

The effect of lithium cation association on the spin density distribution in sym-Trinitrobenzene radical anion has been studied here both experimentally and theoretically. The experimental observations can be satisfactorily explained by simple Huckel molecular orbital calculations only when the cation is assumed to be tightly bound to one of the nitro groups.

The energy of the dihydrated lithium cation Li+·2H2O is studied in several different points within the SCF MO LCAO framework, using a gaussian basis set to approximate the wavefunction. The computed binding energies (hydration energies) and bond distances are compared to the values found for the monohydrate. The results are discussed in view of ion-solvent interaction, and especially of the effect of ions on adjacent hydrogen bonds, in aqueous solutions.

Lithium superoxide has been synthesized by reacting lithium atoms and oxygen molecules at high dilution in inert and oxygen matrices. Isotopic substitution at all atomic positions and use of isotopic mixtures verify the molecular identity and indicate an isosceles triangular structure. Eighteen frequencies from six isotopic molecules determine the potential constants FO–O = 5.59 ± 0.05, FLi–O = 1.18 ± 0.02, and FLi–O,Li–O = − 0.21 ± 0.03 mdyn / A. The oxygen–oxygen force constant for LiO2 coincides with that calculated for O2−, which suggests that the LiO2 molecule is highly ionic and may be considered as a lithium cation bonded to a superoxide anion by Coulombic forces.

The energy surface of the dihydrated fluoride anion (F·2H2O)−1 is studied for a number of different geometry points near the equilibrium structure within the SCF LCAO MO framework, using an extended gaussian basis set to approximate the molecular wavefunctions. For the first and second hydration step of the fluoride anion the corresponding hydration energies are calculated to beB 1 scf =24.1 kcal/mole andB 2 SCF =20.8 kcal/mole (experimental measurements: 23.3 kcal/mole and 16.6 kcal/mole, respectively). The hydration energies and equilibrium bond distances obtained for the dihydrated fluoride anion (F·2H2O)− are compared with those found for the monohydrate (FHOH)− and with corresponding results of the dihydrated lithium cation (Li · 2H2O)+. The system (F·2H2O)− is taken as a very simple model to discuss some basic features of the hydration process of small ions and to study the influence of a negative ion on an adjacent hydrogen bond.

A theoretical consideration of the catalytic activity of group I metal salts, especially of lithium ones, for the homogeneous liquid-phase oxidation of hydrocarbons was developed by extended Huckel molecular orbital calculations, with particular reference to the interaction between the salts and molecular oxygen. We made several findings. First, a marked activity of lithium salt-catalysts was reflected by a remarkable “electron-partial occupation” of the lithium cation in their salts. Second, a strong interaction of the lithium catalyst with O2 occurred at the angle of 15° to the direction of the 1πg-orbital expansions of O2. Third, the lithium catalyst participated strongly in the activation of O2 at the distance of 2 A–3 A, increasing the electron-population of one oxygen atom located farther from the lithium cation. Finally, the contribution of the “activated” oxygen molecule to the initiation of the oxidation of hydrocarbons was discussed.

In Abhangigkeit von der Grose der Substituenten R1 und (insbesondere) R2 verlauft die Enolat-Bildung der Ketone (I) bis zu 100% stereoselektiv zugunsten des Z-Enolats ((II) und (III) werden als Trimethylsilylether bestimmt).

Specific solvation effects on stereoselectivity in the reduction of a cyclohexanone by lithium aluminum tri- t -butoxyhydride have been studied by adding measured quantities of diethyl ether, tetrahydrofuran (THF) and methyl-substituted tetrahydrofurans to benzene solvent, and various amounts of THF to diethyl ether solvent. A steric hindrance effect in the case of bulky addends was observed, and a significant increase in stereoselectivity for less bulky addends was found. The results have been explained in terms of complexing, or steric hindrance to complexing, of the lithium cation.

MP2/6–31G* calculations reveal a significant kinetic acceleration of methyl radical addition to ethylene on complexation of the alkene with the lithium cation, an effect which should be general for alkyl radical addition to alkene–metal cation complexes.

Thecndo/Force method has been employed in the determination of quadratic potential functions for the complexes of lithium cation with formaldehyde and formamide. The O, Li+ stretching frequency and the COLi+ bending frequencies have been estimated after scaling, the stretching and stretch-stretch elements of the force constant matrix. The transferability of the donor potential function to the complex has been verified.

Complexation of alkali cations by macroheterobicyclic ligands leads to a now well-known class of complexes, called cryptates, in which the cation is included within the central molecular cavity of the ligand [1]. Solutions of these alkali metal cryptates have been studied by different techniques [2], however, only few data exist concerning their physicochemical properties in low polarity aprotic solvents [3]. This information is needed in order to elucidate the mechanism and the kinetics of the anionic polymerization of heterocyclic and vinyl monomers with cryptates as counterions [4]. Thus we have examined the behavior and the structure of some lithium ion pairs and of their complexes with cryptands, namely the [211], in THF and in toluene by two complementary techniques : UV and visible spectrophotometry, and by 1H 7Li and NMR.

The CHF-PT-EB-CNDO method has been used to compute the polarisability and second hyperpolarisability of the hydrated lithium cation with one and two hydration shells. The effect of the Li+… (H2O)n interaction on these properties is discussed and the main findings are confirmed in hydrated Na+, Be2+, and Al3+.

In Abhangigkeit von der Grose der Substituenten R1 und (insbesondere) R2 verlauft die Enolat-Bildung der Ketone (I) bis zu 100% stereoselektiv zugunsten des Z-Enolats ((II) und (III) werden als Trimethylsilylether bestimmt).

It has been axiomatic for many years that large rings must be prepared under high dilution conditions so that the probability of the two ends meeting exceeds the probability of linear polymer formation7. It therefore seems remarkable that many of the syntheses of macrocyclic polyethers which have been reported involve less than dilute if not very concentrated conditions18. The success of these large-ring intramolecular SN2 reactions is generally attributed to the operation of a “template” effect during crown synthesis.

Studies of the anionic polymerization of polar vinyl monomers, although very intensive, still remain within the frames of mainly qualitative and semi-quantitative evidence and conclusions. Much of the published data on principle parameters are contradictory and insufficiently reliable. The only exceptions are the polymerizations of methyl methacrylate [1] and the vinyl pyridines [2].

Photoresponsive cyclobutane-1,2-dicarbonyl-capped 2.n diazacrown ethers were prepared by the intramolecular [2 + 2] photocycloaddition of p,p′-trimethylene dicinnamoyl-capped 2.n diazacrown ethers; the cyclobutane-1,2-dicarbonyl-capped 2.1 diazacrown ether showed a highly selective complexing ability for the lithium cation.

Photoresponsive cyclobutane-1,2-dicarbonyl-capped 2·n diazacrown ethers (7) have been prepared by intramolecular [2 + 2]photocycloaddition of p,p′-trimethylenedicinnamoyl-capped 2·n diazacrown ethers (5); the cyclobutane-1,2-dicarbonyl-capped 2.1 diazacrown ether (7a) showed a highly selective complexing ability for the lithium cation, although (5) did not show any complexing abilities for alkali, alkaline-earth, and other metal ions. The crystal structures of (5a), the 1 : 1 lithium and mercury(II) thiocyanate complexes (8) and (9) of (7a) have been determined by X-ray analyses. The structures of (8) and (9) revealed that the configuration of the cyclobutane ring is in the β-form and slightly distorted. Complex (8) consists of dimeric molecules in which the lithium atom is directly bonded to the two oxygen atoms of the amido groups and the two nitrogen atoms of the thiocyanate group of the counter anion and adjacent complex in a slightly distorted tetrahedral configuration. The Hg atom in (9) is also bonded directly to the two oxygen atoms of the amido groups, the two sulphur atoms of the thiocyanate groups, and the simple nitrogen atom of the counter anion of the adjacent complex in a distorted trigonal bipyramidal configuration.

The electronic mechanisms of a model hydride transfer reaction are theoretically studied with ab inito RHF and UHF SCF MO procedures at the 4‐31G basis set level and analytical gradient methods. The model system describes the reduction of cyclopropenyl cation to cyclopropene by the oxidation of lithium hydride to lithium cation. The molecular fragments corresponding to the asymptotic reactive channels characterizing the stepwise mechanisms currently discussed in the literature have been characterized. The binding energy between the fragments is estimated within a simple electrostatic approximate scheme. The results show that a hydride‐ion mechanism is a likely pathway for this particular system. The system is thereafter thoroughly studied from the supermolecule approach. Reaction paths for the ground and first triplet electronic states have been calculated. The hypersurface is explored from a geometrical disposition of the reactants that mimics the one found in several dehydrogenases (perpendicular configuration). A hydride ion is found to be the particle transferred on the unconstrained as well as the constrained reaction pathways in the ground electronic state. In the triplet state (perpendicular configuration) the mechanism is stepwise: electron transfer followed by a hydrogen atom transfer. It has been noticed that the perpendicular geometrical disposition of the reactants plays an important role by polarizing the susceptible cyclopropene C–H bond in the sense of increasing the electronic density at the hydrogen nucleus. This provides a clue to rationalize several dehydrogenase’s active site structure and mechanism. The reactant molecular complex found in the inverted potential energy curves, namely the LiH‐‐‐Cp+ association has an electronic distribution which can be described as a hydride ion cementing two electron deficient centers corresponding to the cyclopropenyl and the lithium cations. Direct CI calculations confirm the overall picture obtained above. Josep.M.Aullo@uv.es

The interaction of hydrogen sulfide and hydrogen persulfide with protons and lithium cations was examined by means of ab initio 6–31G* calculations. The influence of the correlation energy for selected complexes was estimated. Contrary to former results, it can be indicated that second-row hydrides show a consistent interaction behaviour to metal cations and protons. Similarities and differences with the corresponding first-row complexes are discussed.

12-Crown-3 and its hexamethyl derivative, obtained in good yield from oxetane and from 3,3-dimethyloxetane, give stronger complexation than the corresponding 16-crown-4 ligands, and the high selectivity for lithium as compared with sodium and magnesium is retained for Me6-12-crown-3, but is lost for 12-crown-3 owing to the formation of sandwich complexes; X-ray crystal structures are reported for 12-crown-3·LiNCS, Me6-12-crown-3·LiClO4, and Me6-12-crown-3.

Various types of networks containing either an added salt or an ionisable function were thoroughly characterised in order to gain a better understanding of the interactions between ions and polymer segments and of the electrochemical properties displayed as a function of the network structure and the electrolyte.

Life, as we know it, is confined to the chemistry of certain elements. This restriction has been brought about partly by the relative stability of the nuclei of the elements, partly by the kinetic path which produced the different nuclei from protons, and partly by the distribution into which these nuclei have been frozen in planetary systems. Taking these points one at a time, lithium has a nucleus, atomic weight 7, of quite high stability compared with 3H+ + 4 neutrons. Since elements such as hydrogen, with a nucleus of low stability, and carbon, nitrogen, and oxygen, with nuclei of only somewhat greater stability than lithium, are plentiful, lithium should have been present in large quantities on earth. It is not. This is obviously not a consequence of the slow transformation of neutrons and protons to higher elements, which explains the low abundance of atoms of much higher atomic number, e.g., molybdenum, but is now known to be due to the path of nuclear transformations which produced large amounts of carbon and oxygen, but missed lithium (Fig. 1).

Le soluzioni di euglobulina b, estratte da uova non fecondate di axolotl, e quelle di una frazione, che si puo estrarre con identico procedimento dal tuorlo dell'uovo di pollo, non contengono quantita apprezzabili di impurita di origine nucleare. Esse presentano aumento di viscosita ad opera di Li, diminuzione ad opera di SCN', se questi ioni vengono impiegati nelle concentrazioni attive nel produrre modificazioni dello sviluppo embrionale. Viene pertanto confermata la nostra interpretazione sul ruolo dell'euglobulina b nello sviluppo embrionale.