Synthesis and Structural Characterization of Chloro(2,2’;6’,2”-terpyridine)platinum(II) Trichloro(dimethylsufoxide)platinate(II). Density Functional Analysis of the Pt-Pt Interaction in Model Molecules

The addition of a solution of terpy (2,2′;6′,2″-terpyridine) to a solution of cis-[PtCl2(dmso)2] (dmso, dimethylsulfoxide) in acetone, at 25°C, brought to the formation of [PtCl(terpy)][PtCl3(dmso)] (1), as a high yield crystalline red powder, within 12 h. Single crystals of 1 suitable for X-ray diffraction studies were obtained from dmso solution and contain chains of [PtCl(terpy)]22+ dimers (Pt-Pt, 2.338(1) Å) with a Pt···Pt inter-dimer contact distance of 3.419(1) Å. The [PtCl(terpy)]+ moieties have a head-to-tail disposition throughout the chains. The [PtCl3(dmso)]- anions do not have any short internuclear contact but are associated with the chains of cations via (terpy)C-H···Cl and (terpy)C-H···O hydrogen bond type interactions. The [PtCl(terpy)]+ moiety has been simulated via the density functional methods at the B3LYP/LANL2DZ level (6-31G** for Cl), applied to model systems such as [PtCl(NH2)3]2-, [Pt(H2O)4]2+, [PtCl(H2O)3]+, [PtCl(NH=CH-CH=N-C(=CH2)-CH=NH)]+, [{PtCl(NH2)3}{(Pt(H2O)4}], [{PtCl(H2O)2(NH2)}{(PtCl (NH2)3]2-, [PtCl(H2O)3]22+, [PtCl(NH=CH-CH=N-C(=CH2)-CH=NH)]22+. The computed structure for [PtCl(NH=CH-CH=N-C(=CH2)-CH=NH)]+ reproduces well the corresponding moiety of the [PtCl(terpy)]+ cation; for instance, the computed Pt-Cl distance is 2.305 Å, just 0.006 Å smaller than the value found for 1. The optimization of the [{PtCl(NH2)3}{Pt(H2O)4}] neutral molecule which consists of a dianion and a dication brought to a dimer whose Pt-Pt distance is 3.079 Å, much smaller than twice the Van der Waals radius for Pt (1.7-1.8 Å).