The missing agostomer in the fluxionality of cyclohexenylmanganese tricarbonyl

A previously uncharacterized “closed” Cs agostomer of cyclohexenylmanganese tricarbonyl [(C6H9)Mn(CO)3] using DFT computation is proposed. Excellent agreement (R2 = 0.9949) between the computed and experimental 1H NMR chemical shifts is observed. There is reasonable agreement between the computed free energies of activation (6.1, 12.9, and 13.8 kcal mol−1) and experimental free energies of activation (8.3 ± 0.3, 13.1 ± 0.1, and 15.4 ± 0.3 kcal mol−1).192