Molecular Structure and Packing of Platinum(II) Complexes with S-donor Ligands in the Solid State An X-ray Crystallographic Study

How do molecules arrange themselves in a crystal? It is today not possible to definite predict the three-dimensional packing arrangement of molecules in the crystalline solid state. The aim of the work presented in this thesis has been to gain more knowledge of what principles that govern molecular packing.

Platinum(II) complexes have been chosen as model system since these compounds are stable, have a square-planar geometry that allows for interactions directly with the platinum(II) ion and the charge of the complex may easily be changed by changing the ratio between neutral and anionic ligands. Further, the square-planar geometry gives rise to isomerism in some cases.

The investigated compounds are of three types; (i) neutral complexes cis/trans-PtX2L2 with two sulphides and two anionic ligands, (ii) charged complexes with three sulphides and one anionic ligand and (iii) charged complexes with four sulphides or two disulphides. The compounds have been investigated mainly by single-crystal diffraction but also with powder diffraction. Some compounds have been studied at non-ambient temperature and pressure.

Weak hydrogen bonds of the type C-H---A, where A denotes an acceptor atom, is an important interaction in the solid state, and has been studied with A = Cl, Br, I, O and S. Also ?--? interactions have been observed as well as some specific interactions Pt---S and Pt---O. Structural differences in two isostructural pairs of molecules as well as two polymorphs have been analysed. The coordination modes of the nitrato, acetato and dimethyl sulphide ligands have also been studied.

The structural class concept has been applied to compounds of the type cis/trans-PtX2L2 and [PtL4]X2. The predominating structural classes are P2(1)/c, Z=2(-1) (35%) followed by P-1, Z=1(-1) (23%) for trans-compounds and P2(1)/c, Z=4(1) (42%), followed by P-1, Z=2(1) (19%) for cis-compounds.

The compound trans-PtCl2(Me2S)2 has been exposed to pressure in the range 0 - 8 GPa. The compression of the volume in this interval is 26% with largest change along the a-axis.

Two compounds of the type [PtS4](CF3SO3)2 undergo phase transitions at low temperature.