Bromination of a Naphthalene Platinacycle

Bromination of the four-membered Pt(II) metallacycle Pt(Et3P)2(1,8-naphthalendiyl) by Br2 results in
Pt−C bond cleavage and formation of cis-Pt(8-bromonaphthalen-1-yl)(Br)(PEt3)2 (cis-2). Further Br2
addition yields ionic cis-[Pt(η2-8-bromonaphthalen-1-yl)(Br)2(PEt3)2]Br (cis-3) in which the bromine atom
of the bromonaphthalene is bonded to the six-coordinate Pt(IV) center. AgPF6 and cis-3 give AgBr and
cis-[Pt(η2-8-bromonaphthalen-1-yl)(Br)2(PEt3)2]PF6 (cis-4). All of the above complexes isomerize to more
stable trans-complexes. Complex cis-3 slowly converts to neutral Pt(η2-8-bromonaphthalen-1-yl)(Br)3(PEt3) (5) through displacement of a PEt3 ligand by Br-. Photolysis of 5 yields naphthalene, Pt2Br4(PEt3)2, Et3PBr2, and other products. Na/Hg eduction of 5 gives trans-2 and other unidentified products.