Abstract
The 113Cd Fourier transform NMR and Raman spectra (1700-100 cm-1) of a series of Cd(II) chelate complexes (derived from dithiocarbamate, xanthate, dithiophosphinate, and dithiolate ligands), Cd(SCH2CH2OH)2, and [Cd10- (SCH2CH2OH)16]4+ have been determined. Cd-S stretching vibrations have been assigned to bands in the 220-144-cm-1 interval. 113Cd chemical shifts of chelate complexes exhibited no trend in terms of the extent of sulfur ligation, but the nuclear deshielding sequence Cd(SR)2 < Cd(SR)3 < Cd(SR)4 is indicated by measurements on the 1:2 cadmium-(II)-glutathione complex and the decanuclear cation, which contains sites of the latter two types. The solution stability of [Cd10(SCH2CH2OH)16]4+ has been investigated by 1H and 113Cd NMR and Raman spectroscopy from -40 to +100°C. It is concluded that small structural differences may exist between the crystalline and solution phases, arising mainly from partial rupture of [formula omitted] chelate rings known to be present in the crystal, and that the solution structure approaches that in the crystal as solution temperatures are lowered below ca. 20-25 °C. From data obtained in this and previous studies a provisional 113Cd chemical shift scale is presented in terms of the types of ligand atoms in the primary coordination sphere of Cd(II). A conspicuous feature of this scale is the marked deshielding effect of thiolate sulfur vs. oxygen, halide, and nitrogen ligands relative to the reference zero of chemical shift, 0.1 M aqueous Cd(ClO4)2 at 25 °C. Possible application of the deshielding sequence to investigation of cadmium-cysteinate binding in metallothionein proteins is suggested.
Original language | English (US) |
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Pages (from-to) | 2408-2414 |
Number of pages | 7 |
Journal | Inorganic chemistry |
Volume | 15 |
Issue number | 10 |
DOIs | |
State | Published - Oct 1 1976 |