Activation of dioxygen molecules on dinuclear metal centers

Activation of dioxygen molecules on transition metal centers, especially di nuclear metal centers was systematically investigated using hydrotris(3,5-d ialkyipyrazolyl)borate ligands from both organometallic and bioinorganic vi ewpoints. Physicochemical data and X-ray crystallography of synthesized dic opper-O-2 complexes revealed a mu-n(2):n(2) coordination mode which was pro posed as the most probable model of oxyhemocyanin. Dioxygen species bound t o dinuclear cobalt and nickel centers are quite active and react rapidly wi th C-H groups in ligands giving oxygenated products even at room temperatur e. The stability of (mu-n(2):n(2)-O-2)M-2 complexes depends on the electron -donating ability of the central metal atoms and the difference arises main ly from the extent of back donation to the antibonding O-O orbital.