Ammonia as ligand

Section 5.6) to calculate the enthalpy, entropy, and free-energy changes that occur for en to replace ammonia as ligands on Cu(ll) ... 

Neutral and Cationic Ligands. Neutral and cationic ligands are used without change in name and are set off with enclosing marks. Water and ammonia, as neutral ligands, are called aqua and ammine, respectively. The groups NO and CO, when linked directly to a metal atom, are called nitrosyl and carbonyl, respectively. 

The product of this reaction is called a metal-ligand complex. In writing the equation for this reaction, we have shown ammonia as NH3 to emphasize the pair of electrons it donates to Cd +. In subsequent reactions we will omit this notation. 

Silver forms a linear complex ion with 2 neutral ammonia molecules as ligands. 

Sugihara et al. in 1997.106 They utilized aqueous ammonium hydroxide as a reaction medium, which provided ammonia as a hard ligand to labilize the CO ligands and therefore enhance the rate of the PKR. The reaction of dicobalthexacarbonyl complexes of enynes and alkynes provided expected cyclopentenones via intramolecular and intermolecular modes respectively (Scheme 4.10). 

Since the early work dealing with Zeise s salt, many complexes have been prepared with the formula [PtL(C2H4)X2], where L = quinoline, pyridine, or ammonia and X=C1 , Br , I, or N()2. Similar compounds have been prepared that contain other alkenes than C2H4. Many of the complexes containing dienes, trienes, and tetraenes as ligands also contain carbonyl ligands. In fact, metal carbonyls are frequently starting complexes from which alkene complexes are obtained by substitution reactions. 

Both acyclic and cyclic amines, as well as ammonia, can act as ligands, primarily in cobalt(II) and cobalt(III) complexes, so as to produce systems that react with and/or activate dioxygen. With some inevitable overlap, we have separated these topics into distinct sections to aid in the clarity of presentation. 

The complexes with unsubstituted and either alkyl- or aryl-substituted glyoximes have been prepared by the reaction of nickel(II) salts with the appropriate ligand in aqueous or ethanolic solution or an aqueous-ethanolic mixture. In most cases, the reaction is promoted by addition of ammonia as base and/or refluxing temperature. 

For attack of F on acrylic acid, first a hydrogen bonded complex is formed which then proceeds to the transition state and then to a stable carbanion. The methyl in the methacrylic acid reduces stabilization of the carbanion as predicted. Subsequent studies using ammonia as the nucleophile indicated that attack proceeded by a rate-determining intramolecular proton transfer from the nucleophile to the ligand, assisted by a discrete water molecule that acts as a catalyst17. They predicted that acrolein underwent 1,4-addition, acrylic acid either 1,2- or 1,4-addition and acrylonitrile 1,2-addition. 

Experiment Dissolve some copper sulphate pentahydrate CuS04.5H20 in a little water. The solution is light blue, a colour caused by Cu 2+ ions with four water molecules serving as ligands. Now add some drops of concentrated ammonia. The colour will change to a dark blue shade because the NH3 molecules take up the places of the water molecules in the Cu 2+ complex. Note An ammonia solution is toxic. Make certain you work in a well ventilated place. 

Among N-donor ligands, ammonia, aliphatic, aromatic, and heterocyclic amines are widely used as ligands at present (see Sec. 2.2.4.2). Amine complexes are obtained by direct (immediate) interaction of ligands and metal salts, for example (3.8) [8] ... 

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