Scheme 3. Reaction of magnesium(i) complex 3 with methylidene cycloalkanes 4a–b (top). Reaction of magnesium(ii) hydride complex 6 with 7a–d (bottom). Mes = 2,4,6-trimethylphenyl; Dipp = 2,6-diisopropylphenyl. Energies for ΔG^‡_{298 K} in kcal mol⁻¹. 4a (R¹ = R² = Ph), 4b (R¹ = Ph, R² = H), 7a–d (n = 1–4).