Ionic Metal Amides

A variety of basic (nucleophilic) initiators have been used to initiate anionic polymerization [Bywater, 1975, 1976, 1985 Fontanille, 1989 Hsieh and Quirk, 1996 Morton, 1983 Morton and Fetters, 1977 Quirk, 1995, 1998, 2002 Richards, 1979 Szwarc, 1983 Young et al., 1984]. These include covalent or ionic metal amides such as NaNFU and LiN(C2H5)2, alkoxides, hydroxides, cyanides, phosphines, amines, and organometallic compounds such as n-C4H9Li and <)>MgBr. Initiation involves the addition to monomer of a nucleophile (base), either a neutral (B ) or negative (B ) species. 

Ma—Bae may be a covalent or ionic metal amide, alkoxide, alkyl or aryl, or hydroxide depending on the nature of the monomer. M° in equation (4) generally represents an alkali metal which may give up... 

Ionic metal nitrides and amides - react with protonic acids (HX) ... 

Metal nitrides are generally prepared by the direct reaction of the elements. Ionic nitrides are also prepared by the decomposition of metal amides as illustrated by the following reaction ... 

By analogy, ammonium salts should behave as acids in liquid ammonia, since they produce the cation NH4 (the solvo-cation ), and soluble inorganic amides (for example KNHj, ionic) should act as bases. This idea is borne out by experiment ammonium salts in liquid ammonia react with certain metals and hydrogen is given off. The neutralisation of an ionic amide solution by a solution of an ammonium salt in liquid ammonia can be carried out and followed by an indicator or by the change in the potential of an electrode, just like the reaction of sodium hydroxide with hydrochloric acid in water. The only notable difference is that the salt formed in liquid ammonia is usually insoluble and therefore precipitates. 

The [S2N2H] anion (22) is formed by the treatment of S4N4H4 with potassium amide in liquid ammonia.76 Although the [S2N2II] anion has not been isolated as an ionic salt, numerous metal complexes in which 22 acts as a bidentate (S,N) ligand are known. 

The compounds of the amides with bivalentmercuryarecharacteristic. In them the metal is united to the nitrogen and is not in ionic combination, as in a salt. They are formed by the action of mercuric oxide, e.g. 

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