New organoplatinum(II) complexes [PtR₂(PN)] (PN = 2-(diphenylphosphinoamino)pyridine, R = Me, 1a, or p-MeC₆H₄, 1b) were synthesized by the reaction of [Pt(p-MeC₆H₄)₂(SMe₂)₂] or [Me₂Pt(μ-SMe₂)₂PtMe₂ ] with 1 and 2 equiv. of PN, respectively. The reaction of Pt(II) complexes 1 with MeI gave the Pt(IV) complexes [PtR₂(PN)MeI] (R = Me; 2a, and p-MeC₆H₄; 2b). All the complexes were fully characterized using multinuclear (¹H, ³¹P, ¹³C, and ¹⁹⁵Pt) NMR spectroscopy. Density functional theory calculations have been performed to find approximate structures for all described complexes. The platinum(II) complexes have a 5d_π(Pt)-π*(PN) metal-to-ligand charge-transfer band, which was used to easily follow the kinetics of their reactions with MeI. The classical S_N2 mechanism was suggested. The rates of the reactions at different temperatures were measured and were consistent with the proposed mechanism, large negative ΔS^‡ values were found in each reaction. The PN chelating complexes [PtR₂(PN)], 1, reacted almost 100 or 300 times slower with MeI as compared to that of the NN chelating complex [PtR₂(bpy)] (bpy = 2,2′-bipyridine) in acetone or benzene, respectively. This was attributed to the π-acceptance through the P ligating atom of PN ligand, which decreases the electron density of Pt(II) in PN chelating complexes.

A kinetic study of the oxidative addition reaction of diarylplatinum(II) complexes [Pt(p-MeC₆H₄)₂(NN)] (1a: NN = 1,10-phenanthroline (phen) and 1b: NN = 4,4′-di-tert-butyl-2,2′-bipyridine ( ^tBu₂bpy)) with MeI in ionic liquids 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([bmim][bta]) or 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) is described. The reactions were investigated as a function of MeI concentration and temperature under pseudo-first-order conditions using UV-vis spectroscopy techniques. In general, the oxidative addition reactions in ionic liquids followed an S_N2 mechanism, similar to that reported for the related reactions in conventional solvents, e.g. benzene or acetone. The reaction rates in different solvents followed the order acetone > ionic liquids > benzene. The trend in the values of k₂ clearly indicated that ionic liquids behave like conventional solvents and that no particular ‘ionic liquid effect’ was detected in this kind of reaction. The effect of solvent on the reactions was examined using a linear solvation energy relationship (LSER) based on the Kamlet–Taft solvent scale. The activation parameters, ΔH^‡ and ΔS^‡ , were obtained for the reactions in each solvent and the investigation of enthalpy-entropy compensation confirmed that the mechanism operated in all solvents is similar.