Evidence for Formation of a Co–H Bond from (H2O)2Co(dmgBF2)2under H2: Application to Radical Cyclizations

Under H2, the radical cyclization of appropriate dienes can be catalyzed by cobaloximes. H• can be abstracted from an intermediate (presumably a cobalt hydride) by trityl radicals (Ar3C•) or by TEMPO. The rate-determining step in these reactions is the uptake of H2, which is second order in cobalt and first order in hydrogen; the third-order rate constant is 106(3) M–2·s–1.