In contrast, two of the best known aqueous systems that reduce N2 are based on vanadium (55, 56) but are difficult to characterize and mechanistic conclusions are often controversial. Of these, the V(II) catechol system, which functions at alkaline pH, provides a good analog for the reactions catalyzed by nitrogenase. In the absence of N2 this system reduces protons to H2. As with nitrogenase, this reaction, which is inhibited by N2 and the limiting stoichiometry that occurs at room temperature and pressure, is [Pg.99]

A related homogeaous aqueous—alcohoHc system, composed of V(II) complexes of catechol and its derivatives, reduces N2 to ammonia and H2. Only catecholates are active ia this system, which is seasitive to pH. This system has beea likened to nitrogeaase by suggestiag that both use a sequeace of two four-electroa reductioas to evolve oae H2 for every N2 reduced (201). [Pg.92]

Only on rare occasions is it possible to synthesize and purify a whole series of N2 complexes with different ligands the Mo, W, and Re systems shown above are perhaps the most versatile in this respect. N2 can often displace ti -H2, as shown in Eq. 16.25 if this were the last step in the catalytic cycle, it would explain why N2 always produces at least one mole of H2 per mole of N2 reduced. [Pg.443]

In such matters some progress can be achieved by combinations of the decomposition method and the method of separation of variables. For example, this can be done using the method of separation of variables for the reduced system (6) upon eliminating the unknown vectors with odd subscripts j. This trick allows one to solve problem (2) here the expenditures of time are Q 2nin2 og N2 arithmetic operation, half as much than required before in the method of separation of variables. [Pg.651]

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