Alkali Metals In Liquid Ammonia Research Articles

Formation of amidoberyllates from beryllium and alkali metals in liquid ammonia

Abstract Beryllium metal was dissolved in liquid ammonia at ambient temperature through addition of alkali metals. Thereby, the amidoberyllates Cs[Be(NH2)3], [Na4 (NH2)2][Be(NH2)4] and K4[Be2O(NH2)4][Be(NH2)3]2 were isolated and structurally characterized via single crystal X-ray diffraction. In the case of Li we were able to synthesize Be(NH2)2 at ambient temperature. We present the first example of a [Be(NH2)4]2− anion as well as the first oxyamidoberyllate anion [Be2O(NH2)4]2−.

Synthesis of K2Se solar cell dopant in liquid NH3 by solvated electron transfer to elemental selenium

This study explores the rich chemistry of elemental selenium reduction to monoselenide anions. The simplest possible homogeneous electron transfer occurs with free electrons, which is only possible in plasmas; however, alkali metals in liquid ammonia can supply unbound electrons at much lower temperatures, allowing in situ analysis. Here, solvated electrons reduce elemental selenium to K2Se, a compound relevant for alkali metal doping of Cu(In,Ga)Se2 solar cell material. It is proposed that the reaction follows pseudo first-order kinetics with an inner-sphere or outer-sphere oxidation semi reaction mechanism depending on the concentration of solvated electrons.

Convenient access to the tricyanoborate dianion B(CN)₃²⁻ and selected reactions as a boron-centred nucleophile.

Alkali metal tricyanoborates M2B(CN)3 (M = Na, K) are accessible by the reaction of tricyanofluoroborates with alkali metals (i) in liquid NH3 or (ii) in THF-naphthalene. The M2B(CN)3 are versatile starting materials for the synthesis of K[RB(CN)3] (R = Et, C6F5, CH2=CHCH2).

Mechanisms of Two Reduction Reactions under the Condition of Alkali Metal in Liquid Ammonia

Mechanisms of Two Reduction Reactions under the Condition of Alkali Metal in Liquid Ammonia

Reductive Deoxygenation of Alcohols: Catalytic Methods Beyond Barton–McCombie Deoxygenation

AbstractDeoxygenation is an extensively studied field in organic chemistry, and over the last decades many methods such as the Barton–McCombie deoxygenation reaction or deoxygenation with alkali metals in liquid ammonia have been established. Within this microreview, we discuss different strategies for the chemoselective catalytic deoxygenation of alcohols with special attention to their scope and limitations. The deoxygenation of derivatives of alcohols and their direct deoxygenation as step‐economic alternative are covered with current examples. Catalytic methods can serve as convenient and economic alternatives for established methods in the reduction of carbon–oxygen single bonds.

In Situ Dearomatisation/Alkylation of Arylphosphane Derivatives (Eur. J. Org. Chem. 13/2012)

AbstractThe cover picture shows the in situ dearomatisation/alkylation of the aryl substituent in aryldialkylphosphane–borane by a solution of alkali metal in liquid ammonia and alkyl halide. This leads to the formation of α‐substituted (1,4‐cyclohexadien‐3‐yl)phosphane–borane where the “unreactive” phenyl substituent is replaced by a cyclohexadienyl fragment possessing a functionality in the α‐position. This reaction sequence can be regarded as a versatile tool in the “activation” of the aryl substituent in organophosphorus compounds both through aromaticity breaking and introduction of new functionalities at the quaternary α‐carbon atom. Details are discussed in the article by M. Stankevič et al. on p. 2521 ff. The authors would like to express their gratitude to Katarzyna Jaklińska for her efforts during the preparation of the cover picture. magnified image

Evidence for ammonia solvated electrons stabilized at the surface of magnesium oxide

We report on the magnetic properties of solvated electrons localized at the surface of magnesium oxide and obtained by reaction of ammonia with surface excess electrons. Excess electrons can be stabilized at the surface of insulating ionic oxides by strong local potentials of positive and negative ions in particular arrays and in some circumstances by single cations. Exposure of these centres to NH3 leads to ammoniated electrons analogous to those obtained by dissolution of alkali metals in liquid ammonia.

Reductive Activation of Arenes. Part 21. Reaction of Products of Two‐Electron Reduction of Arenecarbonitriles by Alkali Metals in Liquid Ammonia with Bromo‐ and Dibromoalkanes.

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Reduction of p-terphenyl, p-quaterphenyl and p-sexiphenyl using alkali metal in liquid ammonia: Process and characterization of the reduced compounds

Oligomers of PPP ( p-terphenyl, p-quaterphenyl and p-sexiphenyl) were doped using Na or K to promote a reduction. The used method, with liquid ammonia resulted in a solid state doped material without insertion of solvent. The characterization with XPS and Raman spectroscopy showed the formation of at least one phase of the doped oligomer, which contains dianions (bipolarons).

Synthesis and characterization of CuO nanoparticles from liquid ammonia

A new type of CuO nanoparticles were synthesized in liquid ammonia in the presence of sodium metal. First, Cu nanoparticles were obtained by reducing copper nitrate with the alkali metal in liquid ammonia, then, CuO nanoparticles were formed in the ambient conditions. The morphology and structure of as-prepared CuO nanoparticles were characterized by TEM and XRD, and the reason of aggregation of CuO nanoparticles was supposed.

Electron transfer induced dissociations of 2- and 4-alkyl cyclohexadienones

Several 2- and 4-alkylcyclohexadienones were prepared and shown to accept electrons to produce ketyl radical anions that dissociated rapidly at room temperature to release carbon-centered radicals and an aromatic phenoxide type anion. In the PET process with benzyl-substituted cyclohexadienones, initiated with triethylamine, the benzyl radicals dimerised or abstracted an H-atom from solvent. In electrochemical reductions, and in reductions with alkali metals in liquid ammonia, the benzyl radicals were further reduced to anions.

Synthesis, Characterization, and Chemistry of Dimethyl Sulfide Derivatives of closo-B10H102-

The reaction of Cs2[B10H10] with DMSO in acid produces the disubstituted 1,10-, 1,6-, and 2,7(8)-isomers of (Me2S)2B10H8 as well as the monosubstituted [(Me2S)B10H9]- anion. Through a modified procedure, the trisubstituted compound 1,10-(Me2S)2-2-(MeS)B10H7 was prepared and characterized. The 1,10-(Me2S)2B10H8 isomer was converted to the enantiomers 2,7-(Me2S)2B10H8 and 2,8-(Me2S)2B10H8 which were separated on a chiral column. The 1,6-(Me2S)2B10H8 isomer was converted to a mixture of 1,10-(Me2S)2B10H8 and 2,3-(Me2S)2B10H8. These polyhedral rearrangements are believed to occur through the diamond-square-diamond mechanism. The 1,6- and 1,10-(Me2S)2B10H8 isomers were reduced with alkali metal in liquid ammonia to produce the dianions [1,6-(MeS)2B10H8]2- and [1,10-(MeS)2B10H8]2-, respectively. Sodium ethanethiolate was used for the reduction of [1-(Me2S)B10H9]- and 1,10-(Me2S)2B10H8 to form [1-(MeS)B10H9]2- and [1-(MeS)-10-(Me2S)B10H8]-, respectively. The structures of 1,10-(Me2S)2B10H8, 1,6-(Me2S)2B10H8, 2,8-(Me2S)2B10H8, 2,3-(Me2S)2B10H8, 1,10-(Me2S)2-2-(MeS)B10H7, [1-(MeS)-10-(Me2S)B10H8]-, and [1,6-(MeS)2B10H8]2- were determined by single-crystal X-ray diffraction analysis.

Critical points of metallic plasmas and electrolytes

liquid-gas critical point of alkalis and the consolute critical point of alkali metal in liquid ammonia have been theoretically estimated The proximity to the insulator-metal transition suggests a virtual atomic structure of strongly coupled metallic plasmas. In contrast to the OCP model, the estimates for such a structure reasonably agree with available experimental data. Similarly, the critical parameters of charged hard spheres, estimated for a quasimolecular structure, agree with recent Monte-Carlo simulations.

Low-field EPR study of the metal–non-metal transition in sodium–ammonia solutions

Solutions of alkali metals in liquid ammonia show a metal–non-metal (MNM) transition at about 4 mol% metal (MPM). In this paper, we present the results of electron paramagnetic resonance (EPR) studies of sodium–ammonia solutions at 200 MHz as a function of temperature and metal concentration. It has been suggested that the transverse spin relaxation rate consists of two contributions: a hyperfine interaction with 14N nuclei, which is dominant at lower metal concentrations, and a spin–orbit interaction, dominant at higher metal concentrations. The cross-over occurs around 1.5 MPM, a little below the bulk MNM transition point of 4 MPM. From the integrated intensity data of EPR we have examined the spin-pairing equilibrium of excess electrons in the solutions.

Cyclo‐Sb: A New, Highly Charged Zintl Anion, Stabilized as an Ion Complex in the Ammoniate [Li(NH3)4]3[Li2(NH3)2Sb5]·2NH3

The direct reduction of main group metals with alkali metals in liquid ammonia almost seventy years ago got E. Zintl on the trail of the polyanions that were later named after him. The cyclo-Sb ion in the title compound (structure of the [Li2(NH3)2Sb5]3− ion depicted on the right demonstrates that the now feasible structure determination of the unstable ammoniates that are obtained from these solutions may still yield some surprises.

Protonation at the Aromatic Ring of Samarium Benzophenone Dianion Species. Isolation and Structural Characterization of a Samarium(III) Enolate Complex

The reduction of aromatic compounds into their dihydro derivatives by dissolving metal/alcohol systems (the Birch reduction) is a useful methodology in organic synthesis. Of particular importance is the reduction of aromatic carbonyl compounds such as aromatic acids, esters, amides, and monoaryl ketones, which usually generates in situ useful metal enolate intermediates that upon further reaction with electrophiles yield a variety of cyclohexadiene derivatives. One of the possible processes to generate these metal enolate intermediates is thought to be the monoprotonation of dianionic species at the para position of the aromatic rings. On the other hand, the reduction of diaryl ketones by alkali metals in liquid ammonia or by lanthanide metals in THF/HMPA or DME has been well known to afford the corresponding ketone dianions. The first X-ray structure of metal ketone dianion complexes, [Yb([mu]-[eta][sup 1],[eta][sup 2]-OCPh[sub 2]) (HMPA)[sub 2]][sub 2], has been recently determined in this laboratory. Protonation of this complex with ArOH or CpMo(CO)[sub 3]H also occurred at the carbonyl unit to release benzhydrol. In striking contrast to these results, when the analogous samarium benzophenone dianion species was aallowed to react with ArOH, the protonation occurred at the aromatic ring to give a samarium(III) enolate complex. 15 refs., 1more » fig.« less

On the formation and nature of a dipolar Frenkel excitonic insulator

Recently, experiments on expanded fluid mercury, and simulations of alkali metals in liquid ammonia and in molten alkali halides, have motivated interest in the possibility of a Frenkel excitonic insulator (EI) phase. In this paper, the authors discuss several aspects of a model for describing such a phase. They choose a model Hamiltonian which is the asymptotically exact low-density form for a system of atoms each possessing an sp3 basis, and present two methods of analysis. The pairing theory centres on the broadening of the S to P atomic transition into exciton bands, which, as is known, may lead to the formation of a Frenkel EI phase. They analyse two corrections to the traditional exciton picture: (i) double-excitation processes, which are responsible for the van der Waals stabilization energy, are shown to halve the density predicted for the transition to an EI phase; (ii) correct incorporation of non-boson statistics for the exciton operators is argued to drive the transition from first order to second order. The authors also analyse the model Hamiltonian via a Hartree approximation, which proves to be the more tractable method, and further allows an explicit description of the EI phase itself. The validity of the Hartree approximation is justified by comparison with the pairing theory.

ChemInform Abstract: Formation and Reactions of Diorganophosphinite Ions in Liquid Ammonia. Synthesis of Triorganophosphine Oxides by the SRN1 Mechanism.

The reaction of triphenyl- and tribenzylphosphine oxides with alkali metals in liquid ammonia gave diphenyl- and dibenzylphosphinite ions, respectively, in high yields and a small amount of deoxygenated products. These ions reacted under photostimulation with aryl halides by the S RN 1 mechanism to give aryldiphenyl- and aryldibenzylphosphine oxides in good yields. With tribenzylphosphine oxide, by consecutive debenzylation with alkali metals followed by photostimulated reaction with aryl halides, all the benzylic moieties could be replaced by aromatic moieties to finally obtain unsymmetrical triarylphosphine oxides

Formation and reactions of diorganophosphinite ions in liquid ammonia. Synthesis of triorganophosphine oxides by the SRN1 mechanism

The reaction of triphenyl- and tribenzylphosphine oxides with alkali metals in liquid ammonia gave diphenyl- and dibenzylphosphinite ions, respectively, in high yields and a small amount of deoxygenated products. These ions reacted under photostimulation with aryl halides by the S RN 1 mechanism to give aryldiphenyl- and aryldibenzylphosphine oxides in good yields. With tribenzylphosphine oxide, by consecutive debenzylation with alkali metals followed by photostimulated reaction with aryl halides, all the benzylic moieties could be replaced by aromatic moieties to finally obtain unsymmetrical triarylphosphine oxides

ChemInform Abstract: Neighboring Hydroxyl Group Participation in Metal‐Ammonia Reduction of Spirocyclic Dienones.

AbstractReduction of the spirodienone (I) yields the hydroxyspirodienone (II) which is reduced with alkali metals in liquid ammonia to form the hydroxyenones (III) and (IV).