Our goal is to develop convenient methods for obtaining trans-[Pt-II(4-Xpy)(2)Cl-2] complexes applicable to 4-substituted pyridines (4-Xpy) with limited volatility and water solubility, properties typical of 4-Xpy, with X being a moiety targeting drug delivery. Treatment of cis-[Pt-II(DMSO)(2)Cl-2] (DMSO = dimethyl sulfoxide) with 4-Xpy in acetonitrile allowed isolation of a new series of simple trans-[Pt-II(4-Xpy)(2)Cl-2] complexes. A side product with very downfield H2/6 signals led to our synthesis of a series of new [Pt-II(4-Xpy)(4)]Cl-2 salts. For both series in CDCl3, the size of the H2/6 Delta delta [coordinated minus free 4-Xpy H2/6 shift] decreased as 4-Xpy donor ability increased from 4-CNpy to 4-Me(2)Npy. This finding can be attributed to the greater synergistic reduction in the inductive effect of the Pt(II) center with increased 4-Xpy donor ability. The high solubility of [Pt-II(4-Xpy)(4)]Cl-2 salts in CDCl3 (a solvent with low polarity) and the very downfield shift of the [Pt-II(4-Xpy)(4)]Cl-2 H2/6 signals for the solutions provide evidence for the presence of strong {[Pt-II(4-Xpy)(4)](2+),2Cl(-)} ion pairs that are stabilized by multiple CH center dot center dot center dot Cl contacts. This conclusion gains considerable support from [Pt-II(4-Xpy)(4)]Cl-2 crystal structures revealing that a chloride anion occupies a pseudoaxial position with nonbonding (py)C-H center dot center dot center dot Cl contacts (2.43.0 angstrom). Evidence for (py)C-H center dot center dot center dot Y contacts was obtained in NMR studies of [Pt-II(4-Xpy)(4)]Y-2 salts with Y counterions less capable of forming H-bonds than chloride ion. Our synthetic approaches and spectroscopic analysis are clearly applicable to other nonvolatile ligands.