Thermal [1,5] sigmatropic rearrangements in (σ-7-cycloheptatrienyl)triphenyltin and (σ-5-cyclohepta-1,3-dienyl)triphenyltin: A 1H and 13C NMR reinvestigation

It has been confirmed by 1H and 13C NMR spectroscopies that Sn(σ-C7H7)Ph3 undergoes either 1,4- or 1,5-shifts of the SnPh3 moiety around the cycloheptatrienyl ring with ΔH‡ = 13.8 ± 0.4 kcal mol−1, ΔS‡ = −5.6 ± 1.2 cal mol−1 deg−1, and ΔG‡300 = 15.44 ± 0.14 kcal mol−1. Similarly, (σ-5-cyclohepta-1,3-dienyl)triphenyltin undergoes 1,5-shifts with ΔH‡ = 12.4 ± 0.6 kcal mol−1, ΔS‡ = −11.2 ± 1.8 cal mol−1 deg−1, and ΔG‡300 = 15.76 ± 0.13 kcal mol−1. It is therefore probable that Sn(σ-5-C5H5)R3 and Sn(σ-3-indenyl)R3 do not undergo 1,2-shifts as previously suggested but really undergo 1,5-shifts.