Palladium and Platinum Complexes of Bis(alkylthio)alkanes

Torrens M., Hugo (1977) Palladium and Platinum Complexes of Bis(alkylthio)alkanes. PhD thesis, University of Glasgow.

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Novel bis (alkylthio )alkanes containing fluorinated substituents in either the sulphur atoms or the bridge have been prepared by metathetical or photochemical reactions e. g. CF3S- + CH3SCH2CH2Br --> CH3SCH2CH2SCF3 + Br- 2CH3SH + CF3C=CH -hv→ CH3CH(CF3)CH2SCH3 Photolytic reactions of CH3SSCH3 and CH3SH are considered to proceed via CH3S. radicals. Interaction of fluorinated bis (alkylthio )alkanes with [PdCl4]2-or [PtCl4]2- afforded 44 new complexes with the general formula (RSR'Sr'')MX2, where R and R'' - CH3, CF3, C6F5; R' = CH2CH2, CH(CH3) CH(CH3) CF2CH2,CH(CF3)CH(CF3), CH(CF3)CH2; M- Pd, Pt and X= Cl, Br, I; but not all combinations were obtained. Ligands containing both hydrocarbon and fluorocarbon sulphur substituents, e. g. CH3SC2H4SCF3, form 1:1 and 2:1 complexes acting as bidentate or monodentate ligands respectively. In the last case only the CH3S grouping is coordinated and both cis and trans isomers were obtained. No reaction was found to take place between fluorinated sulphides, e. g. CH3SCF3, and either palladium(II) or platinum(II) salts. Differences in the observed chemical reactions of hydrocarbon and fluorocarbon sulphides and dithioethers towards Pd(II) and Pt(II) are discussed in relation to the sulphur-metal bond. X-ray studies of (CF3SCH(CH3) CH2SCF3)PtCl2 have shown that sulphur-platinum bond lengths are slightly shorter than in cis ((p-C6H4Cl)2S)2PtCl2, the most directly comparable structure known. The results have also revealed strong non bonded sulphur-chlorine interactions between pairs of centrosymmetrically related molecules. In solution, all five membered chelate ring complexes exhibit isomerism due to inversion of configuration at sulphur. The total number of stereoisomers depends also on the substituents in the bridge. Thus for compound containing BSCH2CH2SR, RSCH(R)CH2SR and RSCH(R)CH(R)SR ligands, 2, 4 and 6 isomers are possible. N. m. r. spectra of the anti isomers of compounds containing bis (perfluoro-alkylthio)alkanes e. g. (CF3SC2H4SCF3)PtCl2 show fluorine-fluorine coupling between fluorine atoms in different sulphur substituents. This coupling is rationalized in terms of a 'through space' mechanism. N. m. r. spectra of (CF3SC2H4SCF3)PtClBr confirm the proposed structural assignment. The isomeric structure of most platinum compounds have also been tentatively assigned based on n. m. r. parameters. The effect of variable concentration in the bromine substitution reaction involving (CH3SCF3)PtCl2 has been monitored by n. m. r. spectroscopy. Substitution takes place, preferentially trans to the CF3S grouping. Viariable temperature n. m. r. of (CF3SC2H4SCF3)PtCl2 shows that the coalescence temperature of this compound is higher than that found for the corresponding hydrocarbon analogue, probably due to the higher electronegativity and larger mass of the fluorinated substituents. Dynamic n. m. r. studies of (CH3SCH(CF3)CH(CF3)SCH3)PtI2 found two different intramolecular processes: at 183 K the bridge carbon-carbon bond rotation is sufficiently slow to detect the individual resonances arising from two diastereoisomers of a syn isomer. At high temperature the coalescence of resonances arising from anti and syn structures is discussed in terms of sulphur inversion taking place preferentially at single sulphur atoms. Platinum chemical shifts determined for several complexes have been found to be dependent on both the ligands present and the structure of the compounds. The values of d195 Pt for different halide complexes seem to follow additive rules. Values of platinum chemical shift for different stereoisomers of a given complex are qualitatively discussed in terms of intramolecular magnetic fields. Brief studies of reduction and ligand substitution reactions e. g. bis(cyclo-octa-1,5-diene)platinum(0) + CF3SC2H4SCF3, were carried out in an attempt to obtain zerovalent platinum complexes with sulphur containing ligands.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1977
Depositing User: Enlighten Team
Unique ID: glathesis:1977-78774
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 14:55
Last Modified: 30 Jan 2020 14:55

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