HYDROGEN TUNNELING IN THE ACTIVATION OF DIOXYGEN BY A TRIS(PYRAZOLYL)BORATE COBALT COMPLEX

The activation of dioxygen by coordination to metals plays an important role in living organisms as well as artificial oxidation catalysts. We have previously described the dioxygen complex Tp[prime]Co[sup II](O[sub 2]) (Tp[prime] = hydridotris (3-tert-butyl-5-methylpyrazolyl)borate) and its reaction with Tp[prime]Co[sup I](N[sub 2]) to yield Tp[prime]Co[sup II]OH, the apparent product of hydrogen atom abstraction by a highly reactive cobalt - oxo complex. Herein we report related chemistry of the Tp[double prime]Co-moiety (Tp[double prime] = hydridotris (3-isopropyl-5-methylpyrazolyl) borate), including the observation of an intermediate and evidence for a tunneling contribution to hydrogen atom abstraction from the ligand. 16 refs., 1 fig.