A study of sulfur and selenium containing ligands

Tan, Beck Yu Yap (1975) A study of sulfur and selenium containing ligands. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The substituted (arylthio)-, (arylseleno)- and (arylsulfoxy)- acetic acids, RC₆H₄YCH₂CO₂H (Y = S, Se, So; -R = H o, m, p-CH ₃) are studied as ligands towards Pt(II), Pd(II) and Cu(II) ions. The thoi and seleno ligands RC₆H₄XCH₂CO₂H (X = S, Se) form bis-complexes, ML₂, with Pt(II) and Pd(II) whereas the sulfoxy ligands (Y = SO) form only complexed ions (MLX₂)⁻ with Pt(II) and Pd(II) (where X = Cl, Br). -- The bis-complexes of platinum(II) and palladium(II) are coordinated via the thio or seleno group and the carboxylate group of the ligands. The assignment of trans structure is based on the non-coincidence of the υM-O and υM-S bands in the infrared and Raman spectra and also from steric consideration. In these bis-complexes, chelate formation causes magnetic inequivalence of the methylene protons in the ¹H n.m.r. spectra. In addition the presence of chiral centers at sulfur or selenium atoms results in the observations of two sets of methyl and methylene absorptions which coalesce at high temperature. This phenomenon of the ¹H n.m.r. spectra indicates the co-existence of the diastereoisomers (meso and dl). -- (Arylsulfoxy) acetic acid is a potential ambident ligand. In the sulfoxy complexed ions (MLX₂)⁻ the sulfoxy group utilizes the sulfur atom in bonding. The effects of chelatiori and strong electron withdrawing ability of the sulfoxy group render the methylene protons acidic. -- For the bis-complexes of copper(II), CuL₂, (Y = S, Se; R = m or p=CH₃), whether the S or Se atoms participate in the chelate formation is still not clear.

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