Ammonia with multiple bonds

Alkali and alkaline earth metals dissolve in liquid ammonia with the formation of solvated electrons. These solvated electrons constitute a very powerful reducing agent and permit reduction of numerous conjugated multiple-bond systems. The technique, named for Birch provides selective access to 1,4-cydohcxiidicnes from substituted aromatics.8 In the case of structures like 21 that are substituted with electron-donating groups, electron transfer produces a radical anion (here 22) such that subsequent protonation occurs se lectively in the ortho position (cf intermediate 23) A second electron-transfer step followed by another protonation leads to com pound 24... 

Alkilidine tantalum complexes have also been utilized for the preparation of ni-trido Tav. Reaction of ammonia with 31 or 32 afforded nitride 33 in moderate yields [14]. The structure of 33 has been determined by single-crystal X-ray crystallography and shown to consist of a pentameric complex, as depicted in Eq. (9). All of the Ta-N bond lengths are equivalent (2.00 A), suggesting a structure with extensive delocalization of the multiple bonds. 

Note that for the synthesis of heterocyclic compounds one need not have an a-b-c triad in the substrate it is essential that the triad be formed in the course of the reaction with perfluoroolefins. This is natural since substituted thioureas must exhibit the same properties as thiourea itself. This was verified by reference to the reaction of perfluoro-2-methyl-3-isothiocyanatepent-2-ene with ammonia. When ammonia attacks the carbon atom of the N=C=S group, a derivative of thiourea having an a-b-c triad is formed subsequent intermolecular cyclization can occur via an attack of the S-nucleophilic centers at the multiple bond, forming isomeric compound 56 (03UP1). 

The reduction of a carbon-carbon multiple bond by the use of a dissolving metal was first accomplished by Campbell and Eby in 1941. The reduction of disubstituted alkynes to c/ s-alkenes by catalytic hydrogenation, for example by the use of Raney nickel, provided an excellent method for the preparation of isomerically pure c -alkenes. At the time, however, there were no practical synthetic methods for the preparation of pure trani-alkenes. All of the previously existing procedures for the formation of an alkene resulted in the formation of mixtures of the cis- and trans-alkenes, which were extremely difficult to separate with the techniques existing at that time (basically fractional distillation) into the pure components. Campbell and Eby discovered that dialkylacetylenes could be reduced to pure frani-alkenes with sodium in liquid ammonia in good yields and in remarkable states of isomeric purity. Since that time several metal/solvent systems have been found useful for the reduction of C=C and C C bonds in alkenes and alkynes, including lithium/alkylamine, ° calcium/alkylamine, so-dium/HMPA in the absence or presence of a proton donor,activated zinc in the presence of a proton donor (an alcohol), and ytterbium in liquid ammonia. Although most of these reductions involve the reduction of an alkyne to an alkene, several very synthetically useful reactions involve the reduction of a,3-unsaturated ketones to saturated ketones. ... 

In the previous sections we have discussed reactions in which the carbon-azide bond is formed by substitution on carbon of a preformed azide moiety or by its addition to various multiple bonds. Processes in which the azide nitrogen atoms are introduced in a stepwise manner are now considered. These syntheses include the reactions of diazo-nium salts with nucleophiles such as ammonia, chloramine, hydroxyl-amine, hydrazine, sulphonamides and azide ion. Recent work on... 

We have studied the reactions of H3(NS3) with vanadium more thoroughly than those with any other metal, starting from the known [V(0)(NS3)]. Figure 3 shows that the V(NS3) site will support imide, hydrazido, hydrazine, ammonia and nitride ligands, forming multiple bonds to nitrogen species that may be involved in the later stages of reduction of N2. Several of these complexes are... 

For couplings of metallated cyclopropenes with carbonyl compounds liquid ammonia seems to be generally a less suitable solvent since enolizable carbonyl compounds may easily undergo deprotonation under strongly polar conditions, while aldehydes such as benzaldehyde may react with the solvent. For the lithiation of 1-methylcyclopropene both BuLi THF and LDA THF seem suitable systems. We prefer to use, however, the latter base because of its decreased tendency to add across multiple bonds. The thermodynamic basicity of LDA will be sufficient though in the less polar THF the rate of deprotonation might be lower than that with potassium amide in liquid ammonia. 

Power, P. Interaction of Multiple Bonded and Unsaturated Heavier Main Group Compounds with Hydrogen, Ammonia, Olefins, and Related Molecules, Acc. Chem. Res. 2011, 44, 621-631. 

We consider amines, imines, nitriles, and nitro compounds. Ammonia itself is discussed in a section on species with behavior dominated by multiple hydrogen-bonding interactions. 

The Co(III)—C bond in the natural coenzymes is resistant to cleavage in protic solvents. However, the bond length [20] is similar to that in models. Indeed, there appear to be no special corrin ring electronic properties necessary for such water-stable Co—C bonds even Co(III)—CH3 compounds with classical ligands such as ammonia or ethylenediamine have now been discovered [21], Although such non-Bi2-related systems are outside the scope of this review, I believe that the main reason that few such compounds are known lies in the paucity of synthetic routes. Since the Co—C bond, once formed, is relatively inert, such compounds could be used for multiple types of applications such as in molecular assemblies or devices [22], The natural compounds and some models are photosensitive, however [23]. It is this photosensitivity that delayed the discovery of the coenzymes, leading instead to the isolation and characterization of the vitamin [1]. 

The Mossbauer spectrum of ferrous Y-zeolite is somewhat similar to that of the reduced silica gel samples (103). The spectrum consists of two overlapping and partially resolved doublets with the inner doublet, 3 = 0.89 mm sec-1 and A = 0.62 mm sec-1, being attributed to the ferrous ion on the surface. In both the Y-zeolite and the reduced iron oxide on silica samples, the inner doublets representing surface ferrous states are the first to be affected by adsorption of polar molecules, but in the case of Y-zeolite the addition of excess amounts of water or ammonia causes the disappearance of the spectrum, and this has been interpreted in terms of "solvation of the ferrous ions by absorbate causing weakening of the bonding to the crystalline lattice. It is also possible that the spectrum is a composite representing a multiplicity of parameters. 

Feng, W. Y. and Lifshitz, C., Influence of multiple hydrogen bonding on reactivity lon/molecule reactions of proton-bouyid 12-crown-4 ether and its mixed clusters with ammonia and methanol, J.Am. Chem. Soc. 117, 11548-11554(1995). 

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