Linear Bidentate Ligands (L) with Two Terminal Pyridyl N-Donor Groups Forming Pt(II)LCl2 Complexes with Rare Eight-Membered Chelate Rings

NMR and X-ray diffraction studies were conducted on Pt(II)LCl2 complexes prepared with the new N-donor ligands N(SO2R)Mendpa (R = Me, Tol; n = 2, 4). These ligands differ from N(H)dpa (di-2-picolylamine) in having the central N within a tertiary sulfonamide group instead of a secondary amine group and having Me groups at the 6,6′-positions (n = 2) or 3,3′,5,5′-positions (n = 4) of the pyridyl rings. The N(SO2R)3,3′,5,5′-Me4dpa ligands are coordinated in a bidentate fashion in Pt(N(SO2R)3,3′,5,5′-Me4dpa)Cl2 complexes, forming a rare eight-membered chelate ring. The sulfonamide N atom did not bind to Pt(II), consistent with indications in the literature that tertiary sulfonamides are unlikely to anchor two meridionally coordinated five-membered chelate rings in solutions of coordinating solvents. The N(SO2R)6,6′-Me2dpa ligands coordinate in a monodentate fashion to form the binuclear complexes [trans-Pt(DMSO)Cl2]2(N(SO2R)6,6′-Me2dpa). The monodentate instead of bidentate N(SO2R)6,6′-Me2dpa coordination is a...