A Density Functional Theory Study of the Hydrogenation of N 2 Mediated by a Bimetallic Scandium Complex: H 2 Activation and Hydrazido Formation

The utilization of early transition‐metal platforms offers a promising avenue for dinitrogen activation, a key step in developing molecular alternatives for catalytic ammonia synthesis. Herein, we present a density functional theory study exploring N 2 activation and functionalization mediated by an ansa ‐half‐sandwich scandium complex. A thermodynamic evaluation of the bimetallic association of the (C 5 H 4 SiMe 2 N t Bu)Sc monomer with N 2 revealed the formation of a singlet side‐on [(C 5 H 4 SiMe 2 N t Bu)Sc] 2 (μ‐ η 2 : η 2 ‐N 2 ) complex as the global minimum. Electronic properties and an orbital analysis confirmed the effective reduction to a diazenido fragment. Motivated by this finding, the reactivity toward dihydrogen was explored. The energy profile for the hydrogenation of the diazenido moiety resulted in a limiting activation barrier of 31 kcal mol –1 , leading to a hydrazido species [(C 5 H 4 SiMe 2 N t Bu)Sc] 2 (μ‐N 2 H 2 ) with a favourable driving force. Addition of a second equivalent of H 2 resulted in the [(C 5 H 4 SiMe 2 N t Bu)Sc] 2 (H)(μ‐N 2 H 3 ) complex, characterized by a protonated hydrazido and a Sc–hydride. This comprehensive mechanistic insight maps out the sequential hydrogenation capabilities of ansa ‐scandium platforms, defining key electronic factors and reactivity bottlenecks that encourage further developments toward the synthesis of N x H y species from the elemental constituents.