Pt-based polycyclic complex Pt(1,8-naphthalendiyl)(PEt₃)₂ ( 1) undergoes stepwise bromination to give square planar bromo-naphthyl Pt(II) (2) and octahedral Pt(IV) ( 3) complexes. On standing with CD₂Cl₂, 3 replaces one PEt₃ by its Br-ion giving neutral Pt(IV) ( 4) complex, while on heating in CD₂Cl₂, 2 changes its cis-isomeric form to trans complex (5) (Scheme 1). In this context, we will explore the structure-property relationship and the reactivity of the above Pt-based complexes.