Thermal and Photochemical Ring-Bromination in Naphthyl‑, Naphthdiyl‑, and Dicarboximideperyl-Platinum Complexes

Abstract

Brominated polycyclic aromatic compounds are important synthons, but their synthesis can be difficult. Herein, we report that Pt­(IV) centers σ-bonded to naphthalene and a dicarboximideperylene activate the ring systems to selective thermal and photochemical bromination. Thus, <i>trans</i>-Pt­(PEt₃)₂(Br)₃­(4-bromo-1-naphthyl) and Br₂ give <i>trans</i>-Pt­(PEt₃)₂(Br)₃­(7,4-dibromo-1-naphthyl). Introduction of a second Pt­(IV) center is achieved by double oxidative addition of 1,4-dibromonaphthalene to 2Pt­(PEt₃)₄. Bromination of [<i>trans</i>-Pt­(PEt₃)₂Br]₂­(1,4-naphthdiyl) yields [<i>trans</i>-Pt­(PEt₃)₂(Br)₃]₂­(1,4-naphthdiyl), which further brominates on the ring to give [<i>trans</i>-Pt­(PEt₃)₂(Br)₃]₂­(6,7-dibromo-1,4-naphthdiyl). Photoreduction of the Pt­(IV) centers with 1-hexene gives first mixed-valent [<i>trans</i>-Pt­(PEt₃)₂(Br)₃]­[<i>trans</i>-Pt­(PEt₃)₂(Br)]­(6,7-dibromo-1,4-naphthdiyl) and then [<i>trans</i>-Pt­(PEt₃)₂Br]₂­(6,7-dibromo-1,4-naphthdiyl). Photoreduction of <i>trans</i>-Pt­(PEt₃)₂(Br)₃(PMI) (PMI = <i>N</i>-(2,5-di<i>-tert</i>-butylphenyl)­perylen-3-yl-9,10-dicarboximide) without 1-hexene slowly gives ring-bromination at the PMI 12-position. HOTf treatment cleaves the Pt–PMI bond to give 12-bromo-<i>N</i>-(2,5-di<i>-tert</i>-butylphenyl)­perylene-9,10-dicarboximide. The reaction chemistry indicates that the Pt­(IV) center is equivalent to a bulky, electron-donating group for the naphthalene and PMI ring systems