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Lingen V, Lüning A, Krest A, Deacon GB, Schur J, Ott I, Pantenburg I, Meyer G, Klein A. Labile Pd-sulphur and Pt-sulphur bonds in organometallic palladium and platinum complexes [(COD)M(alkyl)(S-ligand)] n+-A speciation study. J Inorg Biochem 2016; 165:119-127. [PMID: 27338203 DOI: 10.1016/j.jinorgbio.2016.06.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 05/10/2016] [Accepted: 06/03/2016] [Indexed: 01/14/2023]
Abstract
Reaction of various sulphur ligands L (SEt-, SPh-, SC6F4H-4-, SEt2, StBu2, SnBu2, DMSO, DPSO) with the precursors [(COD)M(R)Cl] (COD=1,5-cyclooctadiene, M=Pd or Pt; R=methyl (Me) or benzyl (Bn); DMSO=dimethyl sulfoxide; DPSO=diphenyl sulfoxide) allowed isolation and characterisation of mononuclear neutral (n=0) or cationic (n=1) complexes [(COD)Pt(R)(L)]n+. Reaction of l-cysteine (HCys) with [(COD)Pt(Me)Cl] under similar conditions gave the binuclear cationic complex in [{(COD)Pt(Me)}2(μ-Cys)]Cl. Detailed NMR spectroscopy and single crystal X-ray diffraction in the case of [(COD)Pt(Me)(SEt2)][SbF6] and [(COD)Pt(Me)(DMSO)][SbF6] reveal markedly labilised Pt-S bonds as a consequence of the highly covalent Pt-C bonds of the R coligands in these organometallic species. Cationic charge (n=1) seems to lower the Pt-S bond strength further. Consequently, most of these complexes are not stable long-term in aqueous DMF (N,N-dimethylformamide) solutions. This made the evaluation of their antiproliferative properties towards HT-29 colon carcinoma and MCF-7 breast adenocarcinoma cell lines impossible. Only the two complexes [(COD)Pt(R)(SC6F4H-4)] with R=Me or SC6F4H-4 coligands could be tested with the R=Me complex showing promising activity (in the range of cisplatin), while the R=SC6F4H-4 derivative is largely inactive, as were the phosphane complexes [(dppe)Pt(SC6F4H-4)2] (dppe=1,2-bis(diphenylphosphino)ethane), cis-[(PPh3)2Pt(SC6F4H-4)2] and cis-[(PPh3)2PtCl2] which were tested for comparison. In turn, our findings might pave the way to new Pt anti-cancer drugs with largely reduced unwanted depletion of incorporated drugs and reduced side-effects from binding to S-containing biomolecules.
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Affiliation(s)
- Verena Lingen
- Department of Chemistry, Institute for Inorganic Chemistry, University of Cologne, Greinstrasse 6, D-50939 Cologne, Germany
| | - Anna Lüning
- Department of Chemistry, Institute for Inorganic Chemistry, University of Cologne, Greinstrasse 6, D-50939 Cologne, Germany
| | - Alexander Krest
- Department of Chemistry, Institute for Inorganic Chemistry, University of Cologne, Greinstrasse 6, D-50939 Cologne, Germany
| | - Glen B Deacon
- School of Chemistry, Monash University, PO Box 23, Victoria 3800, Australia
| | - Julia Schur
- Institute of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Beethovenstrasse 55, D-38106 Braunschweig, Germany
| | - Ingo Ott
- Institute of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Beethovenstrasse 55, D-38106 Braunschweig, Germany
| | - Ingo Pantenburg
- Department of Chemistry, Institute for Inorganic Chemistry, University of Cologne, Greinstrasse 6, D-50939 Cologne, Germany
| | - Gerd Meyer
- Department of Chemistry, Institute for Inorganic Chemistry, University of Cologne, Greinstrasse 6, D-50939 Cologne, Germany
| | - Axel Klein
- Department of Chemistry, Institute for Inorganic Chemistry, University of Cologne, Greinstrasse 6, D-50939 Cologne, Germany.
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