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 <b>1</b> generates the open-shell, mononuclear Ta­(IV) hydrazido complex <b>2</b>, which upon N-methylation yields the corresponding structurally characterized Ta­(IV) hydrazidium <b>6</b>. Chemical reduction of <b>6</b> results in N–N bond cleavage to generate a cis/trans mixture of the [Ta­(V),Ta­(V)] bis­(μ-nitrido) product <b>7</b> in tetrahydrofuran and the mononuclear Ta­(V) parent imide <b>8</b> 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.