Metal salts Molecular sieves

Phosphorus- chlorine, nitrogen-sulphur carbon type Alkali metal thermionic type Alkali metal salt molecular sieve source, eg CsCI for nitrogen compounds [398]... 

Metal oxides, metal sulfides, metal nitrides, metal carbides, metal borides, metal alloys, metallic glasses, molecular sieves, salts, acids... 

Homoallyl alcohol (3) Metalation of (E) butene (1 05 equiv) with n BuLI (t equiv) and KOtBu (1 equiv) in THF at SO C for 15 mm followed by treatment of (E)-crotyl potassum salt with B(OiPr)3 at 79°C gave after quenching with 1 N HCI and extraction with EtjO containing 1 equiv of diisopropyl tartarate. the crotyl boronate 2 A solution of decanall (156 mg 1 mmol) was added to a toluene solution of 2 (1 1 15 equiv) (0 2 M) at 78 C containing 4A molecular sieves (15-20 mg/L) After 3 h at -78°1 N NaOH was added, followed by extraction and chromatography to afford 208 mg of 3 (90%), anti syn 99 1... 

Zeolites are naturally occurring hydrous aluminum-sodium silicates in porous granule form. They are capable of exchanging their sodium base for calcium or magnesium and of expelling these alkaline earth metals for sodium by treatment with salt. Thus, they are a type of ion-exchange media. (Some zeolites act as molecular sieves by adsorption of water and polar compounds.)... 

Similarly, reactive oxide mixtures are also used to synthesize aluminophosphate molecular sieves, usually starting from phosphoric acid along with the addition of alumina and silica sources analogous to those used in zeolite synthesis with a notable exception alkylammonium salts and amines were ultilized in structure-direchng and space filling to the exclusion of alkali hydroxide solutions and alkali metal salts. 

Amines such as diethylamine, morpholine, pyridine, and /V, /V, /V, /V -tetramethylethylene-diamine are used to solubilize the metal salt and increase the pH of the reaction system so as to lower the oxidation potential of the phenol reactant. The polymerization does not proceed if one uses an amine that forms an insoluble metal complex. Some copper-amine catalysts are inactivated by hydrolysis via the water formed as a by-product of polymerization. The presence of a desiccant such as anhydrous magnesium sulfate or 4-A molecular sieve in the reaction mixture prevents this inactivation. Polymerization is terminated by sweeping the reaction system with nitrogen and the catalyst is inactivated and removed by using an aqueous chelating agent. 

Molecular sieve incidents, 249 Molten metal explosions, 250 Molten salt baths, 250 Molten salts, 251... 

Finally, the remarkably simple solution came from Evans et al. [21a] and researchers of DuPont [21b] simultaneously. Their method allows the coupling of structurally and electronically diverse phenols and aryl boronic acids in the presence of copper]11) acetate, trie-thylamine or pyridine, and molecular sieves at ambient temperature (Scheme 5). Even phenolic amino acid derivatives react smoothly without racemization. The only limitation has been observed when using orfho-heteroatom substituted boronic acids which resulted in lower product yields. The initial step in the proposed pathway (Scheme 6) is the trans-metallation of the boronic acid residue with the copper salt. 

The synthesis of a MeAPO molecular sieve typically uses an aqueous reaction mixture formed by combining a dissolved form of the divalent metal, orthophosphor1c acid, a reactive alumina, and an amine or quaternary ammonium templatlng agent (R>. The metal Is typically Introduced as the acetate or sulfate salt, or as the metal oxide dissolved In dilute phosphoric acid. A synthesis mixture Is prepared In one of two ways ... 

The ability of monomeric Schiff base complexes or polymeric Schiff base ligands to absorb solvent molecules is well-known. Sawodny et al.27) found that the polymer Schiff base complexes exhibit this property much more markedly. The polymers were prepared by the polycondensation reaction of polymer ligands of the Schiff base (29) with metal salts (Eq. 8). The adsorption of solvent is reversible and the ability is dependent upon the nature of the central metal atom and of the ring size around the metal. This profile suggests that the above polymers can be used as a molecular sieve. 

Incorporation of metals in zeolites occurs usually via ion exchange with the respective metal salt and subsequent reduction. A large body of information exists on the preparation and characterization of mono and bimetallic particles in molecular sieves and the reader is referred to that literature for details [197,198,199]. 

---