Theoretical Studies of Inorganic and Organometallic Reaction Mechanisms.20.Carbon -Hydrogen and Carbon-Carbon Bond Activation of Cyclopropane by Cationic Iridium(III) and Neutral Rhodium(I) and Iridium(I) Complexes

摘要

The reaction of cyclopropane with the corrdinately unsaturated species produced by mild thermal activation of [CpIr(P(CH_3)_3)CH_3]~+L(L=Cl_2CH_2, OSO_2CF_3~_) and photochemical activation of CpIr(P(CH_3)_3)L'_2 and CpRhP(CH_3)_3L'_2(L'=H_2, CO)have been investigated with density functional calculations (B3LYP) . The pathway for the production of endo or exo #eta#~3-allyl complexes from the reaction of cyclopropane with the Ir~(III) model complex [CpIr(PH_3)CH_3]~+ proceeds through C-H bond activated Ir~(V) intermdiates and CH_4 elimination, followed by ring opening of the iridium cyclopropyl complexes through and iridium carbene vinyl intermediate to their respective #eta#~3 allyl prodcuts. This unexpected mechanism breaks two C-C bonds simultaneously and then re-forms one en route from the iridium cyclopropane complex to the iridium allyl products. The interconversion between endo and exo #eta#~3-allyl can be assisted by solvent through #eta#~1-allyl intermediate. The Ir~I and Rh~I model complexes CpIr(PH_3) and CpRh(PH_3) react with cyclopropane on their respective singlet potential energy surfaces, first forming a #sigma#-agostic complex followed by a single transition state producing a kinetic product (a hydrido cyclopropyl complex).Thermal rearrangement of the cyclopropyl kinetic product proceeds back through the same sigma#-agostic complex, producting the thermodynamically more stable metallocyclobutane complex