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(PEt<sub>3</sub>)<sub>2</sub>(Br)<sub>3</sub>(4-bromo-1-naphthyl)
and Br<sub>2</sub> give <i>trans</i>-Pt(PEt<sub>3</sub>)<sub>2</sub>(Br)<sub>3</sub>(7,4-dibromo-1-naphthyl). Introduction
of a second Pt(IV) center is achieved by double oxidative addition
of 1,4-dibromonaphthalene to 2Pt(PEt<sub>3</sub>)<sub>4</sub>. Bromination
of [<i>trans</i>-Pt(PEt<sub>3</sub>)<sub>2</sub>Br]<sub>2</sub>(1,4-naphthdiyl) yields [<i>trans</i>-Pt(PEt<sub>3</sub>)<sub>2</sub>(Br)<sub>3</sub>]<sub>2</sub>(1,4-naphthdiyl),
which further brominates on the ring to give [<i>trans</i>-Pt(PEt<sub>3</sub>)<sub>2</sub>(Br)<sub>3</sub>]<sub>2</sub>(6,7-dibromo-1,4-naphthdiyl).
Photoreduction of the Pt(IV) centers with 1-hexene gives first mixed-valent
[<i>trans</i>-Pt(PEt<sub>3</sub>)<sub>2</sub>(Br)<sub>3</sub>][<i>trans</i>-Pt(PEt<sub>3</sub>)<sub>2</sub>(Br)](6,7-dibromo-1,4-naphthdiyl)
and then [<i>trans</i>-Pt(PEt<sub>3</sub>)<sub>2</sub>Br]<sub>2</sub>(6,7-dibromo-1,4-naphthdiyl). Photoreduction of <i>trans</i>-Pt(PEt<sub>3</sub>)<sub>2</sub>(Br)<sub>3</sub>(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
