Browsing by Author "Maisela, Letladi lawrence"

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    Synthesis, characterisation and reactions of ferrocene anchored bis(phosphino) palladium (II) and platinum (II) aryldichalcogenide complexes
    (University of the Western Cape, 2000) Maisela, Letladi lawrence; Darkwa, James; Crouch, Andrew M
    Reactions of M(dppf)Cl2 (M : Pd, Pt) and Pd(dippf)Cl2 with equimolar amounts of the aryldichalcogen reagents, 1,2-benzenedithiol (1,2-(HS)C6H4(SH) (a)), 3,4-toluenedithiol ((HS)C6H3Me(SH)) (b), 3,6-dichloro 1,2-benzenedithiol ((HS)C6H2C12(SH)) (c), 2- mercaptophenol ((HS)C6H4(OH)) (d), thiosalicylic acid ((HS)C6H4(CO2H) (e) and thionicotinic acid (HS)C5H3N(CO2H)) (f) in the presence of triethylamine afforded complexes of the type M(dppf(SC6H4E-o) (where dppf : 1,1'- bis(diphenylphosphino)ferrocene and dippf : 1,1'-bis(diisopropylphosphino)ferrrocene). In addition to the above series, M(dpp0(SC6H5)2 (M : Pd, Pt) and Pd(dippf)(SC6H5)2 were prepared in an attempt to synthesise complexes of the general formula M(dppf)(SC6H4E-o) (M: Pd, Pt; E : Se, Te) via in situ generation of LiSC6H4ELi-o. All complexes isolated were characterised by a combination of IR, 1H, 31P {1H} NMR, mass spectrometry and elemental analysis. Further characterisation of Pd(dppf)(SC6H4S-o), Pd(dippf)(SC6H4S-o), Pd(dippf(SC6H3MeS-o), Pd(dippf)(SC6H5)2, Pt(dppf)(SC6H4S-o) and Pt(dppf)(SC6H4O -o) by single crystal X-ray diffraction studies confirmed the structures deduced from the spectroscopic data. Mass spectrometry data suggests that the Pt(II) complexes are more stable than the analogous Pd(II) complexes. Electrochemical data also show that the dippf complexes were easier to oxidise compared to the dppf, as were the Pd complexes compared to the Pt analogues. In complexes containing homoleptic sulfur ligands (1a-c, 2a-c and 3a-c) the ease of oxidation of the ligand was b > a > c which conforms to either the electron releasing group (b) or an electron withdrawing group (c) on the ligand. Aryldithiolato Pd(dppf) and Pd(dippf) complexes reacted with dimethylacetylene dicarboxylate (DMAD) to form hexamethylbenzene hexacarboxylate (HMBC) and tetramethylcyclobuta-1,3-diene tetracarboxylate (TMCTC) as the dominant products. The same series of aryldithiolato complexes that reacted with DMAD reacted reversibly with sulfur dioxide, a process that was monitored by UV-vis and 1H NMR spectroscopy.