Deuterium and tritium equilibrium isotope effects for coordination and oxidative addition of dihydrogen to [W(CO)5] and for the interconversion of W(CO)5(η2-H2) and W(CO)5H2

DFT (B3LYP) calculations demonstrate that the equilibrium isotope effects (EIEs) for coordination and oxidative addition of H-2 to [W(CO)(5)] do not exhibit a simple exponential variation with temperature; rather, the EIEs exhibit a maximum, with the EIEs being inverse (< 1) at low temperature and normal (> 1) at high temperature. At each temperature, the EIE for coordination of dihydrogen is less than that for oxidative addition, such that the EIE for the interconversion of W(CO)(5)(eta(2)-H-2) is normal, with deuterium favoring the nonclassical (dihydrogen) site at all temperatures.