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

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, trans-Pt­(PEt3)2(Br)3­(4-bromo-1-naphthyl) and Br2 give trans-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 [trans-Pt­(PEt3)2Br]2­(1,4-naphthdiyl) yields [trans-Pt­(PEt3)2(Br)3]2­(1,4-naphthdiyl), which further brominates on the ring to give [trans-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 [trans-Pt­(PEt3)2(Br)3]­[trans-Pt­(PEt3)2(Br)]­(6,7-dibromo-1,4-naphthdiyl) and then [trans-Pt­(PEt3)2Br]2­(6,7-dibromo-1,4-naphthdiyl). Photoreduction of trans-Pt­(PEt3)2(Br)3(PMI) (PMI = N-(2,5-di-tert-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-N-(2,5-di-tert-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.