Nitrogen kinetic inertness

Nitrogen trifluoride is a kinetically inert gas, but when sparked or heated can fluorinate substrates and release nitrogen. Sulfur, for example, is quantitatively converted to SF using NF3 at 5 atm (231). Similarly, boron is converted to BF3 (159) and CF3CN to CF4 (232). Nitrogen trifluoride has some advantages over difluorine. It is safer to handle, and double-compartment bombs to avoid self-ignition are not required. However, some self-dissociation has to be measured and corrections made. 

The configuration of rhenium(I) requires ligand systems which are able to accept electron density from the electron-rich metal center. Thus, frequently phosphines, nitrogen heterocycles, carbonyls, or isocyanides are encountered. Most of the octahedral products possess a high thermodynamic stability and kinetic inertness as is expected for 18-electron systems. 

Sargeson and his coworkers have developed an area of cobalt(III) coordination chemistry which has enabled the synthesis of complicated multidentate ligands directly around the metal. The basis for all of this chemistry is the high stability of cobalt(III) ammine complexes towards dissociation. Consequently, a coordinated ammonia molecule can be deprotonated with base to produce a coordinated amine anion (or amide anion) which functions as a powerful nucleophile. Such a species can attack carbonyl groups, either in intramolecular or intermolecular processes. Similar reactions can be performed by coordinated primary or secondary amines after deprotonation. The resulting imines coordinated to cobalt(III) show unusually high stability towards hydrolysis, but are reactive towards carbon nucleophiles. While the cobalt(III) ion produces some iminium character, it occupies the normal site of protonation and is attached to the nitrogen atom by a kinetically inert bond, and thus resists hydrolysis. 

Figure 3-8. The hydrolysis of a kinetically inert complex containing a monodentate amino acid ester co-ordinated through nitrogen. The only effect of the metal is a long-range polarisation which slightly increases the electrophilic character of the carbonyl carbon atom.

Table 2.3 shows that only one compound, with zinc(II) as the metal ion, seems to have three nitrogens and a water, whereas all the other models have a higher coordination number.The simple [Co "(NH3)50H] + complex has been shown to accelerate the formation of bicarbonate k = 2 x 10 M s ), but, of course, bicarbonate remains coordinated to the metal because of the kinetic inertness of cobalt(III). Some relatively ill-defined systems have been reported to have some kind of activity. The ligand shown in Figure 2.25B, with zinc(II) as the metal ion in H2O, accelerates the attainment of the equilibrium ... 

The challenge to which nitrogenase rises is to break and reduce at a reasonable rate the extremely strong N=N triple bond. The kinetic inertness of N2 is highlighted by the fact that carrying out reactions under nitrogen is considered equivalent to doing the chemistry in an inert atmosphere. Despite this kinetic inertness, thermodynamically the reduction of N2 by H2 is a favorable process,... 

Molecules containing sulfur or nitrogen donor atoms can serve as ligands to form stable complexes with the relatively kinetically inert Pt(II) center (for a review see Ref. 60). It is likely that cisplatin binds to many cellular components, the result of which is general toxicity, but coordination to the heterocyclic nitrogen atoms of DNA nucleobases is most likely responsible for its antitumor activity. 

Separation and purification can also be accomplished by using differences in diffusivities, that is, kinetic separation (discussed in Chapter 3). 4A zeolite has been used in PSA separation for producing nitrogen for inert purge applications... 

N2O is a potentially useful and environmentally friendly oxidant because it is inexpensive and also the only byproduct from an 0x0 transfer reaction would be dinitrogen. However, N2O is extremely (kinetically) inert [187] and is one of the least reactive species among nitrogen oxides. The very large activation energy (59 kcal moh ) [8] for the decomposition of N2O to N2-hO makes it very difficult to use N2O as a practical 0x0 transfer agent at ambient temperature. 

The first time the body realizes that arsenic has been incorporated is when the redox activity (as above) proceeds at potentials when nitrogen or phosphorus are inert. By the time we detect the arsenic poisoning (i.e. we feel unwell), it is generally too late, since atoms of arsenic are covalently bound within body tissue and cannot just be flushed out or treated with an antidote. The arsenic sequesters electrons that might otherwise be involved in other relay cycles, which is a concurrent kinetic process see Figure 8.16. 

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