Imide-nitride reaction

Because the first reaction step in the reaction (6.3) showed quite low equilibrium pressure (Figure 6.1) for the hydrogen desorption due to a large enthalpy change, a number of research groups have focused on the amide-imide reaction instead of the imide-nitride as indicated in reaction (6.4). 

The above reaction is exothermic (AH = -77kJmor ) and occurs within 10 min at 230 °C. The authors propose that by analogy to the amide decomposition in the presence of lithium hydride, the amide-nitride reaction is a two step process which is ammonia mediated. In this case, Li3N (as opposed to LiH) acts as the trap for gaseous ammonia to form the imide in a fast reaction (Eq. 16.12) ... 

Lithium Amide. Lithium amide [7782-89-0], LiNH2, is produced from the reaction of anhydrous ammonia and lithium hydride. The compound can also be prepared by the removal of ammonia from solutions of lithium metal in the presence of catalysts (54). Lithium amide starts to decompose at 320°C and melts at 375°C. Decomposition of the amide above 400°C results first in lithium imide, Li2NH, and eventually in lithium nitride, Li N. Lithium amide is used in the production of antioxidants (qv) and antihistamines (see HiSTAMlNE AND HISTAMINE ANTAGONISTS). 

AIN, GaN, and InN are attractive materials for applications such as blue lasers and field emitters single-source precursors for these of formula [R2MNR 2]2 (R = alkyl, R = alkyl or H) have been reported.236 The reaction of alkylamines with group 13 trialkyl metal compounds affords oligomeric or polymeric ring and cage structures of metal amides and imides (see section on nitrides). 

Another interesting lithium-based system is Li3N/Li2NH [53]. Lithium nitride can be hydrogenated to lithium imide and lithium hydride (5.4 wt% H2). The latter reaction can be used for reversible storage at 250°C. The formation of ammonia can be completely avoided by the addition of 1% TiCl3 to the system, which has the positive additional effect to improve the kinetics [54]. Very fast kinetics has been reported for a partially oxidized lithium nitride [55]. 

The metal amides and imides are important in the nitrogen system. The amides of the active metals are produced by (1) reaction of the metal with NIL, (2) reaction of the metal hydride with NIL, (3) reaction of the metal nitride with ammonia, (4) reaction with another amide, as... 

The preparation of metal nitrides with N3 reagents typically employs d° metal complexes as starting materials. However, the reactions of r-butyl isocyanate with metal-oxo complexes of OsVI and RuVI represent rare examples of the use N3- reagents with d2-metals. It has been postulated that reaction of the isocyanate with metal-oxo 3 affords a four-membered ring intermediate 4, followed by the extrusion of carbon dioxide to yield r-butyl metal imide 5 (Scheme 1). Elimination of isobutylene from this complex then produces the metal nitride and the isobutylene. 

In another recent study, amorphous phosphorus nitride imide (HPN2), a ternary inorganic polymer, has also been prepared via a benzene-thermal reaction of PCI5 and NaN3 under mild conditions [40], The products have interesting morphologies (Fig. 10) of microtubes, hollow balls and square frameworks. Their potential use for industrial application is now under investigation. 

Ge nitride, GesN4, is formed as a black solid from Ge and ammonia at 650 °C, or by heating the imide [Ge(NH)2] at 400 °C. It exists in two forms, both of which have a phenacite-type structure. It decomposes to the elements at 900 °C. GesNq is stable to air and insoluble in HCl, HNO3, H2SO4, and NaOH aqueous. At 700 °C, reaction of Ge3N4 with H2 results in Ge and NH3. 

Step-by-step replacement of the hydrogen atoms in ammonia with metal atoms according to (34) or (35) leads to the amides MNH2, the imides M2NH, and the nitrides M3N. The alkali and alkaline-earth amides can be obtained from the reaction of the hot metals with ammonia. 

NaNH2 contains 5.1 mass% hydrogen. The crystal structure is orthorhombic (Fddd) [72, 73]. On heating, unlike UNH2, molten NaNH2 does not decompose into the imide and ammonia or nitride and ammonia, but seems to decompose into N2, H2 and Na between 400 and 500 °C through some intermediate reactions. 

NH, NHj, NH3, and H species are together larger than the free-site fraction so that Langmuir-Hinshelwood conditions, with only one significant chemisorbed intermediate, do not obtain. In fact, quite early work had already indicated 54) that, in technical catalysis for NH3 synthesis, it is the bonding of Nj (as N) to the catalyst surface which determines the overall rate of the reaction. Correspondingly (55), at moderate temperatures at W, NH3 decomposes giving imide and nitride species on the surface. The rate of decomposition of the nitride species (chemisorbed N) as an intermediate in the NH3 synthesis reaction at Fe was shown by Mittasch et al. (5(5) to be equal to that of NH3 production. 

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... 

The changes in catalytic activities of rare earths introduced into zeolite with the evacuation temperature suggest that the Eu(II) and Yb(II) imide species formed exhibit activity for the isomerization and the Michael reaction (Baba et al. 1993, 1995). Unlike the results on R/C (Imamura et al. 1996a), the nitride species obtained by evacuating R/zeolite around 900 K are catalytically active for the hydrogenation of ethene. However, there is a difference in valence state between europium nitride and ytterbium nitride the former is divalent, while the latter is trivalent. 

The fibers synthesized suggest that the formation of silicon nitride occur in the gaseous phase. However, SigN is not formed from silicon fluoride (SiF ) as was presumed. It is formed from silicon reduced from (NH4)2SiFg hypothetically as imide Si f(NH)j. or amide Si f(NH2)y. This hypothetical scheme is supported by the fact that the reaction 8.20 gives the fibers, where as the reaction 8.14 does not give ones. If the fibers were formed from SiF, both Equations 8.14 and 8.20 reactions would give the fibers. 

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