N–N Bond Cleavage of Mid-Valent Ta(IV) Hydrazido and Hydrazidium Complexes Relevant to the Schrock Cycle for Dinitrogen Fixation

Chemical
reduction of the Ta­(V) hydrazido chloride 1 generates
the open-shell, mononuclear Ta­(IV) hydrazido complex 2, which upon N-methylation yields the corresponding structurally
characterized Ta­(IV) hydrazidium 6. Chemical reduction
of 6 results in N–N bond cleavage to generate
a cis/trans mixture of the [Ta­(V),Ta­(V)] bis­(μ-nitrido) product 7 in tetrahydrofuran and the mononuclear Ta­(V) parent imide 8 in toluene. These results serve to establish an important
foundation for the pursuit of a group-5 metal variant of the Schrock
cycle for dinitrogen fixation.