N anionic

There are notable differences in both structures and stabilities for binary N-O and S-N anions (Section 5.4). The most common oxo-anions of nitrogen are the nitrite [N02] and the nitrate anion [NOs] the latter has a branched chain structure 1.1. The sulfur analogue of nitrite is... 

NMR and visible spectra have established that a number of S-N anions are present in such solutions.The primary reduction products are polysulfides Sx, which dissociate to polysulfur radical anions, especially the deep blue 83 ion (/Imax 620nm). In a IM solution the major S-N anion detected by NMR spectroscopy is cycZo-[S7N] with smaller amounts of the [SSNSS] ion and a trace of [SSNS]. The formation of the acyclic anion 5.23 from the decomposition of cyclo-Sjl is well established from chemical investigations (Section 5.4.3). The acyclic anions 5.22 and 5.23 have been detected by their characteristic visible and Raman spectra. It has also been suggested that a Raman band at 858 cm and a visible absorption band at 390 nm may be attributed to the [SaN] anion formed by cleavage of a S-S bond in [SSNS]. ° However, this anion cannot be obtained as a stable species when [SsN] is treated with one equivalent of PPhs. 

Cyclic selenium imides, e.g., Se7NH, are not available as a source of Se-N anions (Section 6.3). The only example of a metal complex of the [SesN] anion, Pt(Se3N)Cl(PMe2Ph), was obtained by the reaction of Sc4N4 with [PtCl2(PMe2Ph)]2. ... 

Reactions of some heterocyclic carbanions and N-anions with CCI4 and CBr4 990PP359. 

Nevertheless, the adjacent position of the amide and acetylenic groups was used in another type of heterocyclization. The nitrogen atom in the amide group is a weak nucleophile. Therefore, the N anion should be generated by potassium ethoxide. There are two possible variants of nucleophilic addition to the triple bond. Only one takes place, i.e., the formation of y-lactam. After 7 h of heating in EtOH in the presence of KOH, amide 72 isomerized into the known isoindoline 73 in 80% yield (Scheme 128). 

A useful method to synthesize ten and fourteen-membered ring imides 346 involved an initial condensation of macrocyclic -ketoestes 343 with alkyl or aryl isocyanates and carbodiimides, respectively, in the presence of a base [68]. After a nucleophilic attack of the enolate on the isocyanate C, the resultant amide N anion 344 induced a ring closure by addition to the keto group. Then, the intermediately formed four-membered ring 345 underwent a fragmentation... 

Problems and Pitfalls of some Calcium Compounds with (mixed) B,C,N Anions... 

A surprising variety of calcium compounds with combinations of mixed B, C or N anions is known, with some of them listed in Table 8.1. Their structures may contain anionic networks, or very often, triatomic anions with 16 valence electrons, and other anionic species. Some examples of Ca-(B,C,N) compounds are displayed in Fig. 8.1, and will be briefly discussed here. 

S.2 Problems and Pilfalls of some Calcium Compounds with (mixed) B,C,N Anions 123 Table 8.1 Some Ca-(B,C,N) and Ca-CI-(B,C,N) compounds. 

Relatively few investigations involving palladium carbonyl clusters have been carried out, partly because palladium per se does not form stable, discrete homometallic carbonyl clusters at room temperature in either solid or solution states.114,917-922 Nevertheless, solution-phase palladium carbonyl complexes have been synthesized with other stabilizing ligands (e.g., phosphines),105,923 and carbon monoxide readily absorbs on palladium surfaces.924 Moreover, gas-phase [Pd3(CO)n]-anions (n = 1-6) have been generated and their binding energies determined via the collision-induced dissociation method.925... 

Sulfur and nitrogen form a variety of binary anions with acyclic, cyclic and cage structures.69,70 The Se-N anions are only known in metal complexes. S-N anions play an important role in the formation of cyclic sulfur imides and as constituents of solutions of sulfur in liquid ammonia. 

Sulfur dissolves in liquid ammonia to give intensely coloured solutions. The colour is concentration-dependent and the solutions are photosensitive. Several S-N anions are present in such solutions.76,77 The primary reduction products are polysulfides Sx2, which dissociate to polysulfur radical anions, notably the deep blue S3 ion. In a 1M solution, the major S-N anion is cyc/0-[S7N] with smaller amounts of 21 and a trace of 20.76... 

If we consider a symmetric salt of N cations and N anions then the configurational integral is... 

An interesting but still unexplained case refers to nitrobenzene. The reversible electron exchange between nitrobenzeneand sodium salt of the nitrobenzene- N anion-radical is characterized by the usual constant of 0.40. Stevenson et al. (1987b) used NH3(liq) as a solvent for these measurements at -75°C. Under the same conditions, they obtained the equilibrium constant of 2.1( ) for the electron exchange between nitrobenzene- N and the potassium salt of nitrobenzene- " N anion-radical. Perhaps, the difference between ion radii of sodium and potassium cations is crucial for the stability of the corresponding ion pair with nitrobenzene anion-radical. Such diversity can be pivotal when the electron prefers the heavy or light nitrobenzene. 

The ketone receives an electron in the antibonding n MO to form n anion-radical, which is transformed into a (-C-C1) moiety by an intramolecular electron transfer to the antibonding a fragmental orbital of the -C-Cl bond. The (-C-C1) moiety then fragments to form a chloride ion and the corresponding radical (Scheme 7.64). 

The deep blue chromophore ca. 580 nm) formed by deprotonation of S NH was isolated as its tetra-n-butylammonium salt and identified as the S N" anion in 1973 but the structure of this unusual anion remained uncertain until an X-ray crystal structure determination of PPN S N", prepared by the thermal decomposition of PPN SjN in boiling acetonitrile, was reported in 1979... 

Directed metalation by the N-anion of phenothiazines is not confined to /3-lithiation, and it is even more facile when a y-proton is involved. Thus,... 

Figure 13 Qualitative depiction, as functions of the sugar-phosphate C-O bond length, of the energy of a base-sugar-phosphate nucleotide with no electron attached (labeled neutral), with an electron attached to its base n orbital (labeled n anion), and with the electron residing in the sugar-phosphate C-O ct orbital (lower curve) (appears as Figure 7 in ref. 14).

Carbazole can be more easily converted fully and irreversibly to its N-anion by bases stronger than potassium or sodium hydroxide amide and hydride bases under anhydrous conditions have been employed. Thus, sodium amide in liquid ammonia was utilized with the appropriate halide for the preparation of 9-(prop-l-yn-3-yl)carbazole (29 R = CH2C=CH) ° and 9-methylcarbazol-l-ylcarboxylic acid the preparation of 3-dimethylamino-9-(2-hydroxyethyl)carbazole from ethylene oxide utilized sodium amide in... 

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