Isolation of Bis(η<sup>2</sup>-nitrato)(η<sup>4</sup>-cyclobutadiene)cobalt(II) Complexes from the Oxidation of Sterically Hindered CpCo-Stabilized Cyclobutadiene Complexes

The oxidation of sterically hindered, CpCo-protected cyclobutadienes with ceric ammonium nitrate (CAN) yielded the paramagnetic Co(NO<sub>3</sub>)<sub>2</sub>-protected cyclobutadiene products. These half-sandwich complexes represent possible intermediates within the mechanism of the CAN decomplexation of CpCo−cyclobutadiene complexes.