Synthesis and structural characterization of chloro(2,2′;6′,2"-terpyridine)platinum trichloro(dimethylsulfoxide)platinate(II).: Density functional analysis of 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 degreesC, 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)](2)(2+) dimers (Pt-Pt, 2.338(1) Angstrom) with a Pt . . . Pt inter-dimer contact distance of 3.419(1) Angstrom. 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)](2)(2+), [PtCl(NH=CH-CH=N-C(=CH2)-CH=NH)](2)(2+). 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 Angstrom, just 0.006 Angstrom 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 Angstrom, much smaller than twice the Van der Waals radius for Pt (1.7-1.8 Angstrom). (C) 2001 Elsevier Science B.V. All rights reserved.