Kinetics and Mechanism for the Metalation of 5,10,15,20-Tetrakis(pentafluorophenyl)porphyrin with Bis(β-diketonato)copper(II) Complexes in Supercritical Carbon Dioxide and n-Hexane

Abstract

The copper(II) ion incorporation reactions into 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (H2tpfpp) to form the Cu(tpfpp) complex have been kinetically investigated with bis(β-diketonato)copper(II) complexes (CuL2) such as bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)copper(II) (Cu(hfac)2), bis(1,1,1-trifluoropentane-2,4-dionato)copper(II) (Cu(tfac)2), bis(2,2,6,6-tetramethylheptane-3,5-dionato)copper(II) (Cu(hmac)2), and bis(pentane-2,4-dionato)copper(II) (Cu(acac)2) in supercritical carbon dioxide (scCO2) using a previously developed stopped-flow instrument and spectrophotometric cell. Saturation dependence was observed for the conditional first-order rate constants (kobs) as a function of the mole fraction of excess CuL2 (xCu): kobs = k2K1xCu/(1 + K1xCu), where K1 is the preequilibrium constant for the fast outer sphere association between H2tpfpp and CuL2 and k2 is the first-order rate constant for the rate-determining copper(II) ion incorporation into the porphyrin core. Under constant temper...