Molybdenum‐95 Nuclear Magnetic Resonance Signatures of Molybdenum–Imido Olefin Metathesis Pre‐Catalysts

Imido ligands strongly influence high‐valent molybdenum olefin‐metathesis catalysts, yet their electronic impact remains difficult to quantify. Here, a series of Mo(VI)(NAr)Cl 2 (OtBuF 9 ) 2 pre‐catalysts is investigated by 9 5 Mo NMR spectroscopy, catalytic testing, and DFT calculations. Within the aryl‐imido family, electron‐withdrawing substituents give more shielded 9 5 Mo isotropic shifts and higher activities in 1‐nonene self‐metathesis after reduction with 1‐methyl‐3,6‐bis(trimethylsilyl)‐1,4‐cyclohexadiene, whereas electron‐donating substituents show the opposite trend. Shielding‐tensor, natural chemical shielding, and molecular‐orbital analyses show that this correlation is mainly encoded in σ 11 through stabilization of the occupied π(Mo═NAr) HOMO, which reduces paramagnetic deshielding. Comparison with oxo and tert ‐butyl‐imido analogues reveals that similar 9 5 Mo shifts can arise from distinct occupied‐orbital manifolds, making tensor, and orbital analyses essential for interpreting 9 5 Mo NMR descriptors.