Cobalt(III) porphyrin-catalysed hydride reduction of 10-methylacridinium ion and hydrometallation of alkenes and alkynes by tributyltin hydride

Cobalt(III) tetraphenylporphyrin catalyses a hydride transfer reaction from tributyltin hydride to 10-methylacridinium ion via the formation of hydridocobalt(III) tetraphenylporphyrin, which is the rate-determining step, followed by facile hydride transfer from the hydridocobalt(III) porphyrin to 10-methylacridinium ion in acetonitrile. Tributyltin hydride is also effective for the hydrometallation of alkenes and alkynes with cobalt(III) tetraphenylporphyrin to yield the corresponding organocobalt(III) porphyrins regioselectively. The hydrometallation is suggested to proceed via the hydride transfer from tributyltin hydride to cobalt(III) tetraphenylporphyrin to give the hydridocobalt(III) porphyrin, followed by the hydrogen transfer from hydridocobalt(III) porphyrin to alkenes and alkynes to yield the corresponding organocobalt(III) porphyrins. The regioselectivities are consistent with the stabilities of radicals generated by the hydrogen transfer from hydridocobalt(III) porphyrin to alkenes and alkynes. The rates of the electrophilic cleavage of cobalt-carbon bonds of organocobalt(III) porphyrins by trifluoroacetic acid in MeCN are also reported.