Mixed Ligation and Multinuclearity in Metal Sulfide Complexes of Geochemical Interest

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9405432 Helz Much current research is directed toward understanding the behavior of trace metals in anoxic aquatic environments. These studies create a need for accurate data on the stoichiometry and stability of metal complexes containing reduced sulfur ligands. Many existing stability constants are uncertain at the order of magnitude level and thus far less accurate than the field data to which they are applied. In some cases, especially for polysulfide or thiol ligands, no data exist. When data are available, it is often uncertain whether the species described are mononuclear or polynuclear. This proposal request support to continue research on the stabilities of metal sulfide and polysulfide complexes. Our approach combines traditional solution chemistry and EXAFS spectroscopy. In the coming three years, emphasis will be placed on (a) resolving the controversy concerning the nature of arsenic and antimony sulfide complexes (while at the same time exploring the possible importance of thioarsenic and thioantimony as complexing ligands for metals like Cu) (b) developing a continuous flow reactor method and applying it to extend previous work on Zn and Cd sulfide complexes and (c) continuing current work on the role of thiomolybdates as geochemically important ligands and determining the form of Mo in black shales. In the experiments on Cd and Zn sulfides, the possibility of measuring surface energies will be explored.