Comparison of PdII vs RhI-catalyzed catalytic cycle for single step styrene production

Styrene production by a((Fl)DAB)Pd-II(TFA)(eta(2)-C2H4) complex was modeled using density functional theory (DFT). Benzene C-H activation by this complex was studied via five mechanisms, which were oxidative addition/reductive elimination, sigma-bond metathesis, and concerted metalation deprotonation (CMD). The final two mechanisms were calculated without ligated ethylene, CMD activation of ethylene, and benzene substitution of ethylene followed by CMD of the ligated benzene. Calculations provided evidence that conversion of benzene and ethylene to styrene was initiated by the fifth pathway, arylation via CMD of coordinated benzene, followed by ethylene insertion into the Ru-Ph bond, and then beta-hydrogen elimination. The results obtained from present study were compared with that of a recently reported Rh-I complex to help identify more suitable catalysts for the direct production of styrene from ethylene and benzene. (C) 2017 Elsevier B.V. All rights reserved.