The Crystal Structure of {[Pt(9S3)Cl2]2[Pt(9S3)2]}Cl2·4H2O: An Improved Synthesis of [Pt(9S3)Cl2

Abstract

We wish to report the crystal structure for a solid-state solution, {[Pt(9S3)Cl2]2[Pt(9S3)2]}Cl2·4H2O (1), which contains two different complexes of Pt(II) with the trithiacrown 9S3 (1,4,7-trithiacyclononane). One complex [Pt(9S3)Cl2] is neutral and contains a Pt(II) center with a single 9S3 ligand and two coordinated chloro ligands. The second Pt(II) complex is a dication and contains two coordinated 9S3 ligands and two non-coordinating chloride anions. There are two crystallographically equivalent [Pt(9S3)Cl2] complexes present for every single [Pt(9S3)2]2+ cation. Four water solvent molecules are also present. In the neutral complex ([Pt(9S3)Cl2], the Pt(II) center is surrounded by a cis-[S2Cl2 + S1] ligand environment formed by the two chloro ligands and two of the three sulfur atoms from the 9S3 ligand. These two sulfurs are positioned 2.225(2) and 2.242(2) A from the Pt(II), but the third sulfur shows a long distance interaction at 3.311(2) A to form an elongated square pyramidal structure. This axial Pt–S distance is the longest observed in 57 crystal structures of Pt(II) 9S3 complexes. The cation [Pt(9S3)2]2+ displays two centrosymmetrically coordinated 9S3 ligands forming a [S4 + S2] environment with an elongated octahedral shape. In the dication, the two equatorial Pt–S distances are 2.297(2) and 2.306(2) A with the axial sulfur at 3.065(2) A. The most interesting intermolecular aspects of the structure are hydrogen bonding interactions between two of the water molecules and two chloride counter-ions, resulting in a nearly square O2Cl2 ring. This ring shares an edge with a six-membered ring formed by four waters and two chlorides which are hydrogen bonded. The hydrogen bonding interactions, which result from the presence of water in the crystal, appear to be an important component in stabilizing the lattice for the unusual solid-state solution structure. Crystal Data for (1): P2 1 /n, a = 7.8327(10) A, b = 25.152(4) A, c = 12.382(2) A, V = 2314.3(6) A3, Z = 2. We also report an improved synthetic procedure for the preparation of two thiacrown complexes [Pt(9S3)Cl2] and [Pt(10S3)Cl2], which are commonly used as precursors for other heteroleptic thioether complexes. The new syntheses proceed at room temperature without the need for long reflux times and produce large crystals which are easily isolable without filtration. The simplicity of these new preparations results in improved yields over previously employed methods. The title complex crystallizes to form a solid-state solution of two different Pt(II) thiacrown complexes, [Pt(9S3)Cl2] and [Pt(9S3)]2+.