Synthesis of Quinoline-Based Pt–Sb Complexes with L- or Z-Type Interaction: Ligand-Controlled Redox via Anion Transfer

A series of Pt–Sb complexes with two or three L-type quinoline side arms were prepared and studied. Two ligands, tri(8-quinolinyl)stibane (SbQ₃, Q = 8-quinolinyl, 1) and 8,8′-(phenylstibanediyl)diquinoline (SbQ₂Ph, 2), were used to synthesize the Pt^II–Sb^III complexes (SbQ₃)PtCl₂ (3) and (SbQ₂Ph)PtCl₂ (4). Chloride abstraction with AgOAc provided the bis-acetate complexes (SbQ₃)Pt(OAc)₂ (5) and (SbQ₂Ph)Pt(OAc)₂ (6). To better understand the electronic effects of the Sb moiety, analogous bis-chloride complexes were oxidized to an overall formal oxidation state of +7 (i.e., Pt + Sb formal oxidation states = 7) using dichloro(phenyl)-λ³-iodane (PhICl₂) and 3,4,5,6-tetrachloro-1,2-dibenzoquinone (o-chloranil) as two-electron oxidants. Depending on the oxidant, different conformational changes occur within the coordination sphere of Pt as confirmed by single-crystal X-ray diffraction and NMR spectroscopy. In addition, the nature of Pt–Sb interactions was evaluated via molecular and localized orbital calculations.