Nitrogen elemental selenium

The metal reacts directly with elemental carbon, nitrogen, boron, selenium, silicon, phosphorus, sulfur, and with halogens. 

There have been no reports of complexes of " JV-substituted thiosemicarbazones derived from 2-formylpyridine, but 2-acetylpyridine JV-methyl-thiosemicarbazone, 3a, formed [Fe(3a-H)2]C104 and [Fe(3a-H)2]FeCl4 [117]. The nature of these two species was established by partial elemental analyses, molar conductivities, magnetic moments, electronic, infrared, mass and electron spin resonance spectra. A crystal structure of a related selenosemicarbazone complex confirmed the presence of a distorted octahedral iron(III) cation coordinated by two deprotonated anions so that each ligand is essentially planar and the azomethine nitrogens are trans to each other the pyridyl nitrogen and selenium donors are both cis. 

A convenient procedure for the isolation of selenovanadium(IV) porphyrins has been reported and involves the use of Cp2TiSe5 (instead of elemental selenium) (Scheme 21).885,886 The IR spectra exhibit a medium-to-strong band at 434-447 cm-1 assigned to v(V=Se). EXAFS with VSe(OEP) suggests that the V—Se bond is —2.19 A and that the V atom is —0.47 A above the plane of the four nitrogen ligands.128... 

Selenium does not combine directly with nitrogen, but a compound of the two elements, selenium nitride, Se4N4, has been obtained by the... 

Because only a small number of stable selenoketones exist, studies of their decomposition are scarce. Irradiation of dwerf-alkylselones with UV light in hydrogen-donating solvents affords diselenides (80CJC6 87MI1), and the selone 37 behaves likewise. A second path of photolysis involves extrusion of molecular nitrogen from 37 to yield eventually tetramethyl-allene and elemental selenium, probably via the elusive... 

Acetone, 1-butanol, ethanol, methanol, and water are useful solvents for selenourea the solutions in acetone or 1-butanol seem to be the least air-sensitive. Aqueous solutions can be stabilized by the addition of acid. Commercial samples of selenourea are sometimes contaminated with elemental selenium, which can be removed by filtration of the ligand solution. Solid selenourea may be exposed to the atmosphere for short periods without appreciable decomposition, but as a general rule it is advisable to handle selenourea and selenourea complexes in a nitrogen atmosphere and to avoid prolonged exposure to light. 

Hypervalent iodine(III) compounds have found wide application for the oxidation of organic derivatives of nitrogen, sulfur, selenium, tellurium and other elements. Reactions of X -iodanes with organonitrogen compounds leading to the electron-deficient nitrenium intermediates and followed by cyclizations and rearrangements (e.g., Hofmann rearrangement) are discussed in Section 3.1.13. Several other examples of oxidations at a nitrogen center are shown below in Schemes 3.168-3.170. 

A direct procedure to obtain a cycloalkyne from a cycloalkanone involves the conversion into semicarbazone, followed by oxidation with selenium dioxide. The resulting intermediate 1,2,3-selenadiazole can be isolated in pure form and will eliminate, upon heating to 170-220 °C (or refluxing ethylene glycol), elemental selenium and nitrogen, with formation of the cycloalkyne. 

Lanthanum is one of the most reactive of the rare earth metals. It oxidizes rapidly when exposed to air. Cold water attacks lanthanum slowly, and hot water attacks it much more rapidly. The metal reacts directly with elemental carbon, nitrogen, boron, selenium, silicon, phosphorus, sulfur, and with halogens [41]. 

Corriu and coworkers found that the reaction of the pentacoordinated functionalized silane 6 (see also Sections II.B.l and II.C.l) with elemental selenium leads to a stable silaneselone 140, which is stabilized by intramolecular coordination of the nitrogen-containing substituent to the doubly-bonded silicon (Scheme 42) . Although the structure of 140 was supported by Si and NMR and MS spectra, including a downfield Si chemical shift (S = -1-29.4) and a high coupling constant with Se (JseSi = 257 Hz), neither the crystallographical structure analysis nor the reactivity of this isolable Si=Se compound has been reported. 

Iodine forms compounds with all the elements except sulfur, selenium, and the noble gases. It reacts only indirectly with carbon, nitrogen, oxygen, and some noble metals such as platinum. 

Laser isotope separation techniques have been demonstrated for many elements, including hydrogen, boron, carbon, nitrogen, oxygen, sHicon, sulfur, chlorine, titanium, selenium, bromine, molybdenum, barium, osmium, mercury, and some of the rare-earth elements. The most significant separation involves uranium, separating uranium-235 [15117-96-1], from uranium-238 [7440-61-1], (see Uranium and uranium compounds). The... 

Nitrogen and sodium do not react at any temperature under ordinary circumstances, but are reported to form the nitride or azide under the influence of an electric discharge (14,35). Sodium siHcide, NaSi, has been synthesized from the elements (36,37). When heated together, sodium and phosphoms form sodium phosphide, but in the presence of air with ignition sodium phosphate is formed. Sulfur, selenium, and tellurium form the sulfide, selenide, and teUuride, respectively. In vapor phase, sodium forms haHdes with all halogens (14). At room temperature, chlorine and bromine react rapidly with thin films of sodium (38), whereas fluorine and sodium ignite. Molten sodium ignites in chlorine and bums to sodium chloride (see Sodium COMPOUNDS, SODIUM HALIDES). 

The replacement of rhodium from a wide range of rhodacycles to form condensed furans, thiophenes, selenophenes, tellurophenes and pyrroles has been widely explored and a range of examples is shown in Scheme 97. The rhodacycles are readily generated from the appropriate dialkyne and tris(triphenylphosphine)rhodium chloride. Replacement of the rhodium by sulfur, selenium or tellurium is effected by direct treatment with the element, replacement by oxygen using m-chloroperbenzoic acid and by nitrogen using nitrosobenzene. 

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