Scheme 4. Stoichiometric Reactivity of 2_Ph′.

Used either (a) pure or (b) generated by addition of 1 equiv of PhMgBr on 1 followed by 15 h at 20 °C with R′I (R′ = n-C₁₂H₂₅); (c) ³¹P NMR monitoring of reaction of ⁵⁷Fe-2_Ph′ (top) with 3 equiv of n-C₁₂H₂₅I (bottom) during 4 h at 80 °C; (d) plausible catalytic cycle for the cross-coupling of C₆H₆ with R′I involving 2_Ph as a catalyst reservoir (X = Cl, I); (e) cross-coupling attempt performed on PhF (pK_a of the C–H bonds italicized).