N triple bonds

The chemistry of these compounds reflects the unsaturated nature of the B—N triple bond. Polar compounds add to iminoboranes, provided the addition proceeds more rapidly than oligomerization of R SIR ( ). For example, for R = R = CH(CH3)2 or /-C H. ... 

A related example is the reaction of NbCls and thf with (Me3Si)2NN(SiMe3)2 in CH2CI2 to give an 80% yield of [(/Lt-N2) NbCl3(th02 2]- Occasionally an N=N triple bond can be formed within a metal complex, e.g. by reaction of coordinated NH3 with HNO2, but this method is of limited application, e.g. ... 

It is estimated that each year approximately 150 million tonnes of nitrogen are fixed biologically compared to 120 million tonnes fixed industrially by the Haber process (p. 421). In both cases N2 is converted to NH3, requiring the rupture of the N=N triple bond which has the highest dissociation energy (945.41 kJmol )... 

The reactant is adsorbed on the catalyst s surface. As a reactant molecule attaches to the surface of the catalyst, its bonds are weakened and the reaction can proceed more quickly because the bonds are more easily broken (Fig. 13.36). One important step in the reaction mechanism of the Haber process for the synthesis of ammonia is the adsorption of N2 molecules on the iron catalyst and the weakening of the strong N=N triple bond. 

It is then possible to construct reaction schemes to build all of the hydrocarbon molecules observed to date. The reactions with N2 require much shorter wavelength photons to break the N=N triple bond and the chemistry is initiated by cosmic ray (cr) ionisation, with the reactions leading to HCN ... 

Although many complexes of Sc and Y can be seen in the literature, these complexes have been mostly used as Lewis acids in organic synthesis. There are a few examples where addition reactions of organometal species to C=0 double bond, C=N double bond, and C=N triple bond were used in preparation of metal complex. 

Iridium hydride complexes effectively catalyze addition of nitriles or 1,3-dicarbonyl compounds (pronucleophiles) to the C=N triple bonds of nitriles to afford enamines.42S,42Sa Highly chemoselective activation of both the a-C-H bonds and the C=N triple bonds of nitriles has been observed (Equation (72)). To activate simple alkane dinitriles, IrHs(P1Pr3)2 has proved to be more effective (Equation (73)). The reaction likely proceeds through oxidative addition of the a-C-H bonds of pronucleophiles to iridium followed by selective insertion of the CN triple bonds to the Ir-C bond. 

Figure 10.7 During the adsorption of molecular nitrogen onto iron metal, the two nitrogen atoms donate an increment of charge to adjacent atoms of iron on the metal surface, as depicted by the vertical arrows. The N=N triple bond cleaves partially, with a resultant bond order of about 1.5...

By using hydrazine, 3-alkyl-5-aminopyrazoles 584 were formed in excellent yields via conjugate addition, C=C bond migration and intramolecular animation of the C-N triple bond [268]. 

The N=N Triple Bond Activation by Transition Metal Complexes... 

Also, it is worth mentioning (a) the process of N=N triple bond cleavage by Mo(III) complex [6], and (b) the reactivity of coordinated dinitrogen with electrophiles, including the protons and organic free radicals [7], and coordinated [8] and free [9] dihydrogen. 

Since the first step of all of these reactions is dinitrogen coordination to either the surface of the catalyst or transition metal center of the complex, let us briefly discuss the nature and importance of the M-N2 interaction, and the possible coordination modes ofN2 to transition metal centers. These issues were the subjects of many discussions in the literature [10, 11] and it is commonly agreed that the interaction of the N2 molecule with transition metal centers facilitates the activation of the N=N triple bond the stronger the M-N2 interaction, the easier to break the N=N triple bond. 

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