Abstract
This paper reports the kinetics of oxidation of [(Pyr)(n)CuX](4) by O-2 to form the oxidative coupling catalysts [pyr)(n)CuX](4)O-2. The mechanism has been described as a pre-equilibrium, K, between tetranuclear copper(I) and incoming dioxygen, which is followed by rate determining step k(2). The rates of the reaction are reflected to the core structure of [(Pyr)(n)CuX](4), faster for cubane structure as for(X = Cl or Br), when compared to step structure as in case of (X = 1). The overall reaction is a second order process, first order in each [(Pyr)(n)CuX](4) and [O-2], with rate constant k(on) (k(on) = Kk(2)) and exothermic Delta H* varying from -4.9 to -15.5 kcal mol(-1) and Delta S* varying -61.3 to -97.3 cal deg(-1) mol(-1).k(on) were found to be very sensitive to n value 1 or 2.