Dinitrogen Activation at Iron and Cobalt Metallalumatranes

Anionic cobalt and iron metallalumatranes that bind dinitrogen in an end‐on fashion were prepared and characterized by X‐ray crystallography. Along with literature‐known neutral cobalt and iron metallalumatranes, they form a quartet of low‐valent coordination complexes for comparing dinitrogen activation and functionalization at cobalt versus iron centers. In the anionic metallalumatranes, the metal atoms are proposed to have subvalent oxidation states of –1. The electronic structure of the anionic iron alumatrane, which was probed by electron paramagnetic resonance spectroscopy, Mössbauer spectroscopy, and density functional theory, is most consistent with Fe(–1)→Al(+3). Functionalization of dinitrogen was achieved by reaction of the ferrate alumatrane with 1,2‐bis(chlorodimethylsilyl)ethane and KC 8 (1 equiv.) to generate an iron(II) disilylhydrazido complex. The transformation of dinitrogen to disilylhydrazido(2–) is an overall four‐electron process.