Merging Pincer Motifs and Potential Metal–Metal Cooperativity in Cobalt Dinitrogen Chemistry: Efficient Catalytic Silylation of N 2 to N(SiMe 3 ) 3

Using a pyrazolate‐bridged dinucleating ligand that provides two proximate pincer‐type PNN binding sites (“two‐in‐one pincer”), different synthetic routes have been developed towards its dicobalt(I) complex 2 that features a twice deprotonated ligand backbone and two weakly activated terminal N 2 substrate ligands directed into the bimetallic pocket. Protonation of 2 is shown to occur at the ligand scaffold and to trigger conversion to a tetracobalt(I) complex 4 with two end‐on μ 1,2 ‐bridging N 2 ; in THF 4 is labile and undergoes temperature‐dependent N 2 /triflate ligand exchange. These pyrazolate‐based systems combine the potential of exhibiting both metal–metal and metal–ligand cooperativity, viz. two concepts that have emerged as promising design motifs for molecular N 2 fixation catalysts. Complex 2 serves as an efficient (pre)catalyst for the reductive silylation of N 2 into N(SiMe 3 ) 3 (using KC 8 and Me 3 SiCl), yielding up to 240 equiv N(SiMe 3 ) 3 per catalyst.