The oxidation of square-planar cyclometalated Pt(II) phenylpyridine species using the electrophilic chlorine based oxidant PhICl2 has been studied. Rapid oxidations are observed in chloroform solvent at −40 °C leading to single products. In acetone solvent isomeric forms of the product are formed, and these are observed to isomerize at around −10 °C. The oxidation of a complex with an uncyclometalated pendant arm resulted in the very rapid cyclometalation of that arm by the resulting electrophilic Pt(IV) species.