Facile formation and redox of benzoxazole-2-thiolate-bridged dinuclear Pt(II/III) complexes

Reaction of [Pt(L)(mu-Cl)](2) (L = ppy (2-phenylpyridine) or bzq (benzo[h]quinoline)) with 2-mercaptobenzoxazole (NOSH) and NaOAc in THF at r.t. yields the dinuclear Pt(II) d(8)-d(8) complexes [Pt2L2(mu-NOS-kappa N,S)(2)] (L = ppy, 1; L = bzq, 2) and the Pt(III) d(7)-d(7) complexes [Pt-2(ppy)(2)(mu-NOS-kappa N,S)(2)(NOS-kappa S)(2)] (L = ppy, 3; L = bzq, 4) in one pot. The C,N-cyclometalated ligand is chelating whereas the N,S-donating benzoxazole-2-thiolates doubly bridge the two metal centers. The Pt center dot center dot center dot Pt separations of 3.0204(3) and 2.9726(8) angstrom in 1 and 2 contract to 2.685(1) angstrom in 3 and 2.6923(3) angstrom in 4, respectively, when two S-bound thiolate ligands coordinate trans- to the Pt center dot center dot center dot Pt axis. However, cyclometalation is preserved and there is minimum perturbation of the bridging ligands. Complexes 3 and 4 can be also obtained by oxidative addition of the thiolate ligand. In the presence of NaBH4, 3 and 4 can be reduced to 1 and 2, respectively. At r.t., 1 and 2 exhibit intense orange-red luminescence at 625 nm and 631 nm, respectively. The electrochemical properties of 1-4 have been also discussed.