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

Abstract

Reaction of [Pt(L)(μ-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) d⁸–d⁸ complexes [Pt₂L₂(μ-NOS-κN,S)₂] (L = ppy, 1; L = bzq, 2) and the Pt(III) d⁷–d⁷ complexes [Pt₂(ppy)₂(μ-NOS-κN,S)₂(NOS-κS)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⋯Pt separations of 3.0204(3) and 2.9726(8) Å in 1 and 2 contract to 2.685(1) Å in 3 and 2.6923(3) Å in 4, respectively, when two S-bound thiolate ligands coordinate trans- to the Pt⋯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.