Dynamic N2 Binding at High-Spin Co(I) Supported by N,N,C Heteroscorpionates

Controlling N2 binding at transition-metal centers is essential in facilitating its rapid functionalization. Herein, we report the synthesis of high-spin four-coordinate Co–N2 complexes bound by our recently developed class of N,N,C heteroscorpionate ligands. End-on bridging and terminal binding modes for Co-bound N2 are both readily accessed by adjusting the steric profile of the supporting ligand. In the reported complexes, N2 is only weakly bound and is reversibly lost upon application of vacuum or an Ar atmosphere, with concomitant formation of an unusual Co–C–Si 3-center–2e– interaction. This work further demonstrates the power of steric control in modulating small-molecule binding at low valent centers.