Base-Promoted Vinyl Carbon–Bromine Bond Cleavage by Group 9 Metalloporphyrin Complexes

Base-promoted vinyl carbon–bromine bond cleavage of styryl bromide by group 9 metalloporphyrin complexes was achieved to give the metal­(III) porphyrin styryls M­(ttp)­(styryl) (ttp = 5,10,15,20-tetra-p-tolylporphyrinato dianion). Mechanistic studies suggest that [MII(ttp)]2 (M = Rh, Ir) cleaves the vinyl C–Br bond via an addition–elimination mechanism. The much less reactive CoII(ttp) undergoes a radical recombination with styryl radical which is generated by the hydroxide reduction of styryl bromide to give a radical anion with subsequent C–Br cleavage.