Dinitrogen complexes protonation

W(NNH)(thf)(Ph2PCH2CH2PPh2)2l . This reduces under dinitrogen to reform the parent dinitrogen complex.. Protonation of the regenerated dinitrogen complex with tosylic acid completes the cycle [2]. In so far as the inputs N2, and e lead to ammonia at ambient... 

This process is an indirect ammonia synthesis. There are three steps including formation of dinitrogen complex, protonation and eduction of ammonia. This method requires complete destruction of complex, otherwise, the N-N bond cannot be disbanded and an effective synthetic cycle for ammonia cannot be realized. The effective way to solve this problem is to supply extra electron by chemistry or electrochemistry in order to realize controllable break of N-N bond and a synthetic recycle from nitrogen to ammonia. ... 

The alternative mechanistic scenario for the protonation and reduction of end-on terminally coordinated N2 through the Schrock cycle is represented by the Chatt cycle which has been developed many years earlier (5). This system is based on Mo(0) and W(0) dinitrogen complexes with phosphine coligands (Fig. 3). As expected, the intermediates of the dinitrogen reduction scheme are very similar to those of the Schrock cycle. Moreover, a cyclic generation of NH3 from N2 has been demonstrated on the basis of this system, however, with very small yields (3,4a). In order to obtain general insight into the mechanism of the Chatt cycle we have studied most of the intermediates of Fig. 3 with... 

The [MoOI(prP4)] precursor 3 was finally converted to the corresponding dinitrogen complex by electrochemical reduction with a Hg pool electrode in the presence of dinitrogen and phenol. The latter reagent was added as a weak acid to induce protonation of the oxo group and subsequent elimination as water. The blue solution of the Mo oxo complex thereby turned... 

Their proton base strengths are less than that of the dinitrogen complex, but greater than that of the hydrazido(2 -) complexes.139 Their structures are likely to be similar to those of the alkyldiazenido complexes discussed below, that is trans octahedral with a linear MoNN system and NNH = 120°, but definite evidence is lacking. 

The photolysis of [Os(NH3)5N2l2 and Os(NH3)4(N2)2 2 f at 229-366 nm is complex. The mono(dinitrogen) complex loses dinitrogen, aquates, and is oxidized by protons, and the resultant reaction manifold is complicated. The bis(dinitrogen) complex solely photoaquates yielding 0s(NH3)4(H20)N212+ which can also oxidize. For both com-... 

An in situ 15N-NMR study of the protonation reactions of molybdenum and tungsten dinitrogen complexes has shown that signals arise in the early stages of the reaction which can be assigned to relatively stable hydrazido(2-) species (4). With careful choice of acid and conditions, thermally stable hydrazido(2-) complexes can be isolated. They often yield ammonia and/or hydrazine upon further protonation (4,105), for example, reaction (43). 

Only those Mo(0) and W(0) dinitrogen complexes which possess at least one (labile) monotertiary phosphine ligand give ammonia upon protonation complexes such as phosphine ligand by an anion increases the basicity of the... 

The formation of ammonia and/or hydrazine by protonation of binuclear bridging dinitrogen complexes of Groups IV and V is well established and has been reviewed elsewhere (82, 148). In general, stoichiometries are fairly well defined [Eq. (51)], although as with mononuclear complexes, mechanisms are not clearly understood (282). 

The first site of protonation in a dinitrogen complex, based on mechanistic studies of complexes, must be the dinitrogen itself, yielding the diazenido species (N2H). If protonation occurs at the metal then reaction proceeds no further, or results in the loss of coordinated dinitro-gen. The formal insertion of dinitrogen into a metal-hydride bond (a popular proposal in the early chemical nitrogen-fixation literature) is unknown. 

Protonation of the dinitrogen complex I gives the NNH2 complex [WF(NNH2)(depe)2]BF4 (III). As Raman spectra of III were found to be almost featureless, vibrational information on this system has exclusively been obtained from infrared spectroscopy. Figure 4 shows the MIR and FIR spectra of III and its 15N and 2H isotopomers 15N-III and 2H-III, respectively. Seven peaks can be recognized to shift upon... 

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