Katarzyna Grubel - Alkali Metal Control over N-N Cleavage in Iron Complexes

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      Publication Details (including relevant citation   information):

      Grubel, K.; Brennessel, W. W.; Mercado, B. Q.; Holland, P. L.   Journal of American Chemical Society  2014, 136, 16807-16816.

      Abstract:

     
        Abstract Image 
     

        Though N2 cleavage on K-promoted Fe surfaces is     important in the large-scale Haber–Bosch process, there is     still ambiguity about the number of Fe atoms involved during     the N–N cleaving step and the interactions responsible for the     promoting ability of K. This work explores a molecular Fe     system for N2 reduction, particularly focusing on     the differences in the results obtained using different alkali     metals as reductants (Na, K, Rb, Cs). The products of these     reactions feature new types of Fe–N2 and Fe-nitride     cores. Surprisingly, adding more equivalents of reductant to     the system gives a product in which the N–N bond is not     cleaved, indicating that the reducing power is not the most     important factor that determines the extent of N2    activation. On the other hand, the results suggest that the     size of the alkali metal cation can control the number of Fe     atoms that can approach N2, which in turn controls     the ability to achieve N2 cleavage. The accumulated     results indicate that cleaving the triple N–N bond to nitrides     is facilitated by simultaneous approach of least three     low-valent Fe atoms to a single molecule of N2.  

      Address (URL): http://pubs.acs.org/doi/abs/10.1021/ja507442b