Dihydrogen with dinitrogen

The reaction of Cr(CO)5(C6H12) with dinitrogen is similar to that with dihydrogen (99) [Eq. (12)]. 

The direct use of ammonia or dinitrogen and hydrogen to synthesize imido amido complexes is essentially pioneers territory [58, 59]. Recently, we have formed, by surface organometaUic chemistry, a well-defined Ta amido imido species by reaction with either ammonia [9] or with dinitrogen and dihydrogen at subatmospheric pressure [60]. 

The catalyst used throughout the study was 0.66% w/w Pt/alumina (B.E.T. surface area 184 mV). Sample weights of between 0.20 g. and 0,55 g, were used and these were reduced at 873 K in a 2% dihydrogen in dinitrogen stream (GHSV = 2950 hr-1) for 30 min. before use. After reduction the catalysts were flushed with helium at the reduction temperature and the temperature adjusted to the reaction temperature in a helium flow. The labelled gases used in the course of the study were [2H]dihydrogen (Cambrian Chemicals pic), [2-13C]-propane and... 

Intermediates in the Fixation of Dinitrogen. There are still no spectroscopically detected intermediates in the reduction of dinitrogen to ammonia. We believe, however, that the electron balance studies with nitrogenase under dinitrogen/dihydrogen and dinitrogen/dideuterium atmospheres point to the existence of such intermediates. The stoichiometry for the HD formation reaction as determined experimentally is shown in Reaction 6. At first glance, this resembles the substrate reactions... 

While the latter reactions are no longer used for nitrogen fixation, the reaction of dinitrogen with dihydrogen to form ammonia is among the most important industrial processes. The alkaline-earth metals react readily with dinitrogen at elevated temperatures to form nitrides lithium reacts even at room temperature with dinitrogen. 

Reacting dinitrogen with dihydrogen on a catalytic iron surface (the Haber-Bosch process)... 

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. 

Below, we plan to discuss only the reactivity of the coordinated dinitrogen with dihydrogen molecules. 

For example, the above presented theoretical results and comparison of those with available experiment clearly indicate that addition of the second (and third) hydrogen molecule to complex [p2n2]Zr( i-Ti2-N2)Zr[p2n2], A1 should be feasible under appropriate laboratory conditions, and formation of ammonia from dinitrogen and dihydrogen molecules could be a catalytic process (see Figure 11). This conclusion should be tested by experimentalists. 

In summary, the tantalum hydride system adds to the few previously reported well-defined organometallic complexes capable of cleaving N-H bonds of ammonia to yield either an amido or an imido complex, and achieves unprecedented dinitrogen N=N triple bond cleavage with dihydrogen on isolated tantalum atoms to yield reduction of both N atoms. 

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