Oxygen with alkali metals

Figure 4.11 Molecular structures of typical crown-ether complexes with alkali metal cations (a) sodium-water-benzo-I5-crown-5 showing pentagonal-pyramidal coordination of Na by 6 oxygen atoms (b) 18-crown-6-potassium-ethyl acetoacetate enolate showing unsymmelrical coordination of K by 8 oxygen atoms and (c) the RbNCS ion pair coordinated by dibenzo-I8-crown-6 to give seven-fold coordination about Rb.

K.J. Maynard, and M. Moskovits, A surface enhanced Raman study of carbon dioxide coadsorption with oxygen and alkali metals on silver surfaces,/. Chem. Phys. 90(11), 6668-6679 (1989). 

Metal ketyls are ion-radicals analogous to semiquinone ion radicals and may be considered either oxygen or carbon free radicals. They are readily prepared by treating aromatic ketones with alkali metals in dry ether, benzene, or liquid ammonia under an inert atmosphere.124 125 Benzophenone potassium has been shown to be paramagnetic in the solid state.126... 

Monensin belongs to the family of polyether ionophores. These compounds consist of a series of tetrahydrofuran and tetrahydro-pyran rings and have a carboxyl group that forms neutral salts with alkali metal cations. Their three-dimensional structure presents a lipophilic hydrocarbon exterior with the cation encircled in the oxygen-rich interior. They probably act by transporting cations through the lipid bi-layer of cell membranes, thereby preventing the concentration of potassium by the cells. Evidence for this is... 

Investigations of the generation of super base sites on alkaline earth metal oxides by doping with alkali metals (246,247,253) led to the inference that when zero-valent alkali metals react with a metal oxide surface, the electron donated by the alkali metal to the oxide lattice resides in a defect site, such as an oxygen vacancy, generating a one-electron donor site (F center) (254,255) (Scheme 40). 

A triply chelating ligand is the purpurate anion, (/), the ammonium salt of which is the indicator murexide. The kinetics of its complex formation with alkali metals have been reviewed (75). In the lithium salt the cation is 5-coordinated in a square pyramid with the base formed by the three donor atoms, 0, N, O from one anion and a carbonyl oxygen from... 

LiAlH4 as this avoids protonation of the enolate and the production of any over-reduction products. Cholest-4-en-3-one may be reduced to cholestanone (5a 5/8,1 19) with alkali-metal carbonyl chromates. The studies on intramolecular hydride shifts on hydroxy-ketones and -aldehydes have been extended. " The hydride shifts were examined in a number of y- and 5-hydroxy-carbonyI compounds by heating the substrates with alkaline alumina containing D2O. Exchange of protons on the carbon a to both oxygen functions signals the intramolecular hydride shift typically, the hemiacetals (95) and (96) each incorporate up to six deuterium atoms. The general conclusion, in common with literature precedent, is that, whereas 1,5-shifts are common, 1,4-shifts are rare. 

Binary Selenides. Most binary selenides are formed by heating selenium in the presence of the element, reduction of selenites or selenates with carbon or hydrogen, and double decomposition of heavy-metal salts in aqueous solution or suspension with a soluble selenide salt, eg, Na2Se or (NH Se [66455-76-3]. Atmospheric oxygen oxidizes the selenides more rapidly than the corresponding sulfides and more slowly than the tellurides. Selenides of the alkali, alkaline-earth metals, and lanthanum elements are water soluble and readily hydrolyzed. Heavy-metal selenides are insoluble in water. Polyselenides form when selenium reacts with alkali metals dissolved in liquid ammonia. Metal (M) hydrogen selenides of the M HSe type are known. Some heavy-metal selenides show important and useful electric, photoelectric, photo-optical, and semiconductor properties. Ferroselenium and nickel selenide are made by sintering a mixture of selenium and metal powder. 

TPA forms coordination complexes with a variety of metal ions. Poten-tiometric studies of TPA complexes with Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Pb(II), Hg(II), and Ag(I) have been reported.5 Spectroscopic and/or crystallographic studies have also been reported for TPA complexes with alkali metal cations,6 7 V(IV),8 Co(III),2 Fe(III),9 10 Mn(III),11 Cu(I),12 Cu(II),13,14 and Zn(II).15 Copper1316-18 and iron19,20 complexes of TPA have been used to model biological oxygen binding and activation. 

A study of the interaction of ligand (88) with alkali metal complexes has been reported.423 The NaNCS complex contains the ligand bound to the Na+ by five oxygen donors but the sulfur does hot interact at all the six coordination of the cation is completed by the NCS- anion.424 The KNCS complex has the metal at the centre of a hexagon of donors, all of interact with the metal, 2S and in the RbNCS complex the Rb+ sits out of the plane towards an N-bonded NCS- anion and is also coordinated by a sulfur from an adjacent ring to give a dimeric structure.426... 

Complexes with Oxygen Macrocycles Figure 15.14 summarizes log K values for the complexes of the 15C5 macrocycle with alkali metal cations, and the 18C6 macrocycle with both alkali metal and alkaline earth metal cations.cc The log K results for these systems were determined from calorimetric measurements. Values are plotted against the ratio of the cation crystal radius to the radius of the hole in the center of the macrocycle.dd... 

A major use of ethers in the organic laboratory is as solvents for reactions. Ethers are nonpolar enough to dissolve many organic compounds, and the electrons on the oxygen can interact with alkali metal cations to help solubilize salts. In addition, ethers are nonacidic and are not very reactive. For these reasons they are especially useful in reactions involving strongly basic reagents. In addition to diethyl ether, other ethers that are commonly used as solvents are 1.2-dimethoxyethane (DME) and the cyclic ethers tetrahydrofuran (THF) and 1,4-dioxane ... 

Another class of macrocyclic molecules for binding with alkali metal cations is cahx[n]arene (n = 4,6,8) and its derivatives. They are made up of phenol and methylene units which provide a rigid arrangement of various number of oxygen donor atoms for metal complexation. Some of them are proved to display exceptional selectivity for K+ and Cs+ 131 Further details of this developing field will be found in Macrocyclic Ligands. 

Oxygen radical anions ( 3.8). The O center can be formed by various means on the surface, not only by doping the material with alkali metals ions. O exhibits an high chemical reactivity and can be located at low-coordinated sites as well as at regular terrace sites. 

The compounds of hexavalent americium with alkali metals have little thermal stability. At 550°C. (Me = Li) and 700°C. (Me = Na) there is a loss of oxygen, and compounds with pentavalent americium are formed (31). The continued thermal decomposition in the system Li20-Am02-02 results directly in Am02 above 900°-1000°C. whereas the decomposition of Na3Am04 leads to Am02 via Na2Am03. The indi-... 

Univalent nickel ions can be prepared both on the intracrystalline surface and at fully coordinated positions by heating NiUY with alkali metal vapour. The surface Ni ions are chemically very reactive but thermally unstable those at fully co-ordinated positions are thermally stable even at 400°C, and are inert to H2, NH3, and CO although they react with oxygen to form O J. 

The alkali-metal X and Y zeolites react with alkali metal vapour to form coloured products of non-stoichiometric compositions containing the paramagnetic centres Na + and Na . The Na + centres are stable up to 500°C and they react reversibly with gases with oxygen they form Oj radicals. 

Oxygen-sulfur heteroatom exchange has been achieved with 3-methyl-benzene thiazole-2-thione in the presence of trifluoroacetic acid and with l-phenyl-5-mercaptotetrazole. Thiirane can be prepared from oxirane on a support impregnated with alkali metal salts, by decomposition of the dithiocarbon-ate formed with carbon disulfide. A macrocyclic ether, perhydrobenzo-18-crown-6, plays a role in the nucleophilic reaction of oxirane with KCNS, which leads to thiirane in good yield. ... 

Sulphur forms more stable complexes than oxygen with these metals. In alkali metal polysulphide solutions, HgS gives the HgS - ion. The metal halides all form addition compounds with thioethers (Fig. 284). 

It is worthwhile to point out that the alkali fullerides are extremely air-sensitive. All sample preparations with alkali metals must be carried out in a glove box with oxygen levels on the order of one part per million. However, prepared samples can survive some exposure to air.[Ho91a ]... 

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