NMR and X-ray diffraction studies were conducted on Pt(II)LCl2 complexes prepared with the new N-donor ligands N(SO2R)Me(n)dpa (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'-Me(4)dpa ligands are coordinated in a bidentate fashion in Pt(N(SO2R)3,3',5,5'-Me(4)dpa)Cl-2 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'-Me(2)dpa ligands coordinate in a monodentate fashion to form the binuclear complexes [trans-Pt(DMSO)Cl-2](2)(N(SO2R)6,6'-Me(2)dpa). The monodentate instead of bidentate N(SO2R)6,6'-Me(2)dpa coordination is attributed to 6,6'-Me steric bulk. These binuclear complexes are indefinitely stable in DMF-d(7), but in DMSO-d(6) the N(SO2R)6,6'-Me(2)dpa ligands dissociate completely. In DMSO-d(6), the bidentate ligands in Pt(N(SO2R)3,3',5,5'-Me(4)dpa)Cl-2 complexes also dissociate, but incompletely; these complexes provide rare examples of association dissociation equilibria of N,N bidentate ligands in Pt(II) chemistry. Like typical cis-PtLCl2 complexes, the Pt(N(SO2R)3,3',5,5'-Me(4)dpa)Cl-2 complexes undergo monosolvolysis in DMSO-d(6) to form the [Pt(N(SO2R)3,3',5,5'-Me(4)dpa)(DMSO-d(6))Cl](+) cations. However, unlike typical cis-PtLCl2 complexes, the Pt(N(SO2R)3,3',5,5'-Me(4)dpa)Cl-2 complexes surprisingly do not react readily with the excellent N-donor bioligand guanosine. A comparison of the structural features of over 50 known relevant Pt(II) complexes having smaller chelate rings with those of the very few relevant Pt(II) complexes having eight-membered chelate rings indicates that the pyridyl rings in Pt(N(SO2R)3,3',5,5'-Me(4)dpa)Cl-2 complexes are well positioned to form strong Pt-N bonds. Therefore, the dissociation of the bidentate ligand and the poor biomolecule reactivity of the Pt(N(SO2R)3,3',5,5'-Me(4)dpa)Cl-2 complexes arise from steric consequences imposed by the -CH2-N(SO2R)-CH2- chain in the eight-membered chelate ring.