AbstractThe syntheses and single‐crystal X‐ray structures of a series of Mo–imido alkylidene N‐heterocyclic carbene (NHC) complexes (1–15) and of the first complexes containing bidentate NHC‐phenolate ligands (16–18) are reported. Mo(N‐2,6‐Me2‐C6H3)((1‐R‐phenethyl)‐3‐mesitylimidazolidin‐2‐ylidene)(CHR)(OTf)2 (R=CMe2Ph, 1) is the first enantiomerically pure Mo–imido alkylidene NHC catalyst. With [Mo(N‐2,6‐Me2‐C6H3)(IMes)(CHR)(CH3CN)(OTf)(CH3CN)+ B(ArF)4−] (7), turnover numbers up to 545 000 were achieved in the homometathesis (HM) of 1‐octene and 1‐nonene (≤95 % E). With 7 and 1‐nonene, a turnover frequency (TOF4 min) of 8860 min−1 was determined. Productivity and E/Z‐selectivity were correlated with catalyst structure. For 1, Mo(N‐3,5‐Me2‐C6H3)(IMesH2)(CHR)(OTf)2 (9) and Mo(N‐3,5‐Me2‐C6H3)(IMes)(CHR)(OTf)2 (10), productivity was correlated with the coalescence temperature of the two triflates, determined by variable‐temperature 19F NMR spectroscopy. The square‐planar conformer is postulated to be the most relevant for the catalyst activation.