The One-Electron Oxidation of an Azazirconacyclobutene in the Presence of B(C6F5)3

Erker has used B(C{sub 6}F{sub 5}){sub 3} to generate active olefin polymerization catalysts by opening zirconacycles. In an effort to extend this work a heteroatom-substituted zirconacycle was treated with B(C{sub 6}F{sub 5}){sub 3}. The result is a partial oxidation to a radical cation. A typical {sup 1}H NMR of the heteroatom-substituted zirconacycle after the addition of B(C{sub 6}F{sub 5}){sub 3}. One set of phenyl resonances has broadened to the point of disappearance: The t-Bu signal has broadened substantially: the other phenyl resonances did not broaden significantly; the chemical shifts remain unchanged. Less broadening is observed when smaller amounts of B(C{sub 6}F{sub 5}){sub 3} are added. There is no immediate change in the {sup 19}F NMR of the B(C{sub 6}F{sub 5}){sub 3}. Such selective broadening has been seen in the {sup 1}H NMR spectrum of partially oxidized chlorophyll a and explained by electron exchange with the corresponding radical cation.