Metal amides (systematic namemetal azanides) are a class ofcoordination compounds composed of a metal center with amide ligands of the form NR2−. Amido complexes of the parent amido ligandNH2− are rare compared to complexes with diorganylamido ligand, such as dimethylamido. Amideligands have two electron pairs available for bonding.
![Tris(dimethylamino)aluminium dimer[1]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aTris(dimethylamino)aluminium_dimer.png)
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In principle, the M-NX2 group could be pyramidal or planar. The pyramidal geometry is not observed.
In many complexes, the amido is abridging ligand. Some examples have both bridging and terminal amido ligands. Bulky amide ligands have a lesser tendency to bridge. Amide ligands may participate in metal-ligand π-bonding giving a complex with the metal center being co-planar with the nitrogen and substituents.Metal bis(trimethylsilyl)amides form a significant subcategory of metal amide compounds. These compounds tend to be discrete and soluble in organic solvents.
Lithium amides are the most important amides. They are prepared fromn-butyllithium and the appropriate amine
The lithium amides are more common and more soluble than the other alkali metal analogs. Potassium amides are prepared by transmetallation of lithium amides withpotassium t-butoxide (see alsoSchlosser base) or by reaction of the amine withpotassium,potassium hydride,n-butylpotassium, orbenzylpotassium.[2]
The alkali metal amides, MNH2 (M = Li, Na, K) are commercially available. Sodium amide (also known as sodamide) is synthesized fromsodium metal andammonia withferric nitrate catalyst.[3][4] The sodium compound is white, but the presence of metallic iron turns the commercial material gray.
Lithium diisopropylamide is a popularnon-nucleophilic base used inorganic synthesis. Unlike many other bases, thesteric bulk prevents this base from acting as anucleophile. It is commercially available, usually as a solution in hexane. It may be readily prepared fromn-butyllithium anddiisopropylamine.
Amido derivatives of main group elements are well developed.[5]
Early transition metal amides may be prepared by treating anhydrous metal chloride with alkali amide reagents. In some cases, two equivalents of a secondary amine can be used, one equivalent serving as a base:[6]
Transition metal amide complexes have been prepared by these methods:[6]
Highly cationic metal ammine complexes such as [Pt(NH3)6]4+ spontaneously convert to the amido derivative:
Transition metal amides are intermediates in the base-induced substitution oftransition metal ammine complexes. Thus, theSn1CB mechanism for the displacement of chloride fromchloropentamminecobalt chloride by hydroxide proceeds via an amido intermediate:[8]
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