Redox chemistry and H-atom abstraction reactivity of a terminal zirconium(iv) oxo compound mediated by an appended cobalt(i) center

The reactivity of the terminal zirconium(iv) oxo complex, O[triple bond, length as m-dash]Zr(MesNP(i)Pr(2))(3)CoCN(t)Bu (2), is explored, revealing unique redox activity imparted by the pendent redox active cobalt(i) center. Oxo complex 2 can be chemically reduced using Na/Hg or Ph(3)C(•) to afford the Zr(IV)/Co(0) complexes [(μ-Na)OZr(MesNP(i)Pr(2))(3)CoCN(t)Bu](2) (3) and Ph(3)COZr(MesNP(i)Pr(2))(3)CoCN(t)Bu (4), respectively. Based on the cyclic voltammogram of 2, Ph(3)˙ should not be sufficiently reducing to achieve the chemical reduction of 2, but sufficient driving force for the reaction is provided by the nucleophilicity of the terminal oxo fragment and its affinity to bind Ph(3)C(+). Accordingly, 2 reacts readily with [Ph(3)C][BPh(4)] and Ph(3)CCl to afford [Ph(3)COZr(MesNP(i)Pr(2))(3)CoCN(t)Bu][BPh(4)] ([5][BPh4]) and Ph(3)COZr(MesNP(i)Pr(2))(3)CoCl (6), respectively. The chemical oxidation of 2 is also investigated, revealing that oxidation of 2 is accompanied by immediate hydrogen atom abstraction to afford the hydroxide complex [HOZr(MesNP(i)Pr(2))(3)CoCN(t)Bu](+) ([9]+). Thus it is posited that the transient [OZr(MesNP(i)Pr(2))(3)CoCN(t)Bu](+) [2](+) cation generated upon oxidation combines the basicity of a nucleophilic early metal oxo fragment with the oxidizing power of the appended cobalt center to facilitate H-atom abstraction.