The type of chemical reaction between hapten and carrier protein in the formation of a complete antigen in vivo giving rise to an allergic contact dermatitis (ACD, type IV allergy) is essentially unknown. About 4,000 low-molecular organic compounds are known to have allergenic properties. α,β-Unsaturated carbonyl structures are frequently present among these compounds. Haptens giving rise to antibody formation and type I allergy have been shown to add predominantly to lysine in the carrier protein. In this paper, the reactivity of activated type IV haptens to a model peptide is reported. Essentially all amino acids with nucleophilic properties were present in the model peptide. Investigation of the relative reactivities of the amino acid residues to activated haptens under biomimetic conditions is performed in order to determine the proportions between the adducts of the different amino acid moieties. In all cases, the electrophilic α,β-unsaturated haptens were found to be added to the cysteine residue and no lysine adduct was recorded. Nuclear magnetic resonance (NMR) spectroscopy was used to exclude steric hindrance of any amino acid residue in the addition reaction. The hapten-modified peptides were isolated and characterized by NMR and mass spectrometry.

trans-PtCl(2)(dms)(2) (dms is dimethyl sulfide) crystallizes in the space group P2(1)/n and adopts the molecular point group C(i), which is the most frequently occurring point group for trans-PtX(2)L(2) complexes (78%), as observed in the Cambridge Structural Database (CSD; 2005 release), followed by C(1) (16%). Density functional theory calculations show that the observed geometry for trans-PtCl(2)(dms)(2) has slightly higher energy than the most favorable geometry in the point group C(2h), but this geometry would require a space group that hampers close packing, thus showing that intermolecular forces determine the point group for the title compound. High-pressure powder diffraction studies of trans-PtCl(2)(dms)(2) show no phase transformation up to 8.0 GPa. The bulk modulus is 8.1 (6) GPa and the pressure derivative 8.1 (4). In the CSD, the number of cis- and trans-PtX(2)L(2) compounds are almost equal, viz. 156 cis and 160 trans compounds, showing no preference for either isomer in the solid state.

The title compounds, chlorotris(dimethyl sulfide-kappaS)platinum(II) hexafluorophosphate, [PtCl(C(2)H(6)S)(3)]PF(6), and bromotris(dimethyl sulfide-kappaS)platinum(II) hexafluorophosphate, [PtBr(C(2)H(6)S)(3)]PF(6), are isomorphous and are composed of [PtX(dms)(3)](+) complex cations (X = Cl and Br, and dms is dimethyl sulfide) and PF(6)(-) anions. The Pt atom is coordinated by three S atoms and one X atom in a pseudo-square-planar coordination, with Pt-S distances in the range 2.293 (1)-2.319 (2) A. Two dms ligands have a staggered conformation with respect to the coordination plane, while the third is rotated by approximately 90 degrees compared with the orientation of the other two. The packing can be described as consisting of [PtX(dms)(3)](2)(PF(6))(2) units with a centre of symmetry. In this description, the Pt(II) atom has a pseudo-octahedral coordination, with four normal bonds and two long weak interactions. Density-functional theory calculations show that a conformation in which one dms ligand is not staggered is less favourable than having all three dms ligands staggered.

The structures of two polymorphs, one triclinic and one monoclinic, of cis-dichlorobis(dibenzyl sulfido-kappaS)platinum(II), cis-PtCl(2)(Bz(2)S)(2), have been determined at 295, 250, 200, 150 and 100 K. In both polymorphs the complex has a structure where platinum(II) coordinates two dibenzyl sulfide molecules and two chloro ligands, forming a complex with pseudo-square-planar coordination geometry. The triclinic polymorph shows disorder at all temperatures. Both polymorphs have a packing arrangement involving centrosymmetric structural dimers. cis-PtCl(2)(Bz(2)S)(2) belongs to a group of complexes with the general formula PtX(2)L(2), where X is a halogen and L is a ligand with a donor atom from groups 14, 15 or 16. The distribution of structural classes among 173 cis-PtX(2)L(2) compounds found in the Cambridge Structural Database (CSD, Version 5.28, November 2006) has been investigated. The predominant structural class [notation according to Belsky & Zorkii (1977). Acta Cryst. A33, 1004-1006] among the cis compounds is P2(1)/c, Z = 4 (1) (73 structures, 42%), followed by P\bar 1, Z = 2 (1) (33 structures, 19%). Inversion centres combined with the screw-axis/glide plane are the dominating packing operators (56%) followed by the inversion centre (21%). The cis and trans influence in cis/trans-PtCl(2)L(2) compounds has been investigated using data from the CSD. The cis influence is small for donor atoms in groups 15 and 16. The trans influence is small for group 16 donor atoms and for nitrogen, but for phosphorus it is significantly greater than the other donor atoms studied.

The title compound, cis-[PtCl(2)(C(4)H(10)S)(2)], crystallizes in the space group P2(1)/n with pseudo-square-planar coordination geometry. The orientation of the ethyl groups on the S atoms is staggered with respect to the coordination plane, giving the complex approximate C(2v) symmetry. The complex does not form dimeric packing units with short Pt...S intradimeric distances as seen in some related complexes, but instead displays C-H...Cl interactions in three dimensions. These C-H...Cl-Pt contacts are compared with those of related compounds reported in the Cambridge Structural Database, which show a frequency maximum in the range 120-170 degrees for the C-H...Cl angle.