Abstract
In aqueous organometallic chemistry water is often considered solely as a solvent. However, there are several examples when such an assumption is not justified [1]. Water is a strongly coordinating, polar solvent, capable of assisting reactions yielding polar or charged (ionic) products. H2O itself can oxidatively add to a low valent transition metal complex with formation of hydrido-hydroxometal complex compounds. Hydroxometal species are also formed by replacement of anionic ligands (e.g. halides) by OH- (metal ion hydrolysis equilibria). Dissolved salts strongly influence reaction mechanisms involving polar or charged transition states and intermediates. In addition acid/base catalytic reactions of the substrates or products effect rates and selectivities. All these reactions are influenced by the pH which should be regarded of paramount importance in aqueous organometallic catalysis. Presence of a separate water phase in aqueous/organic biphasic reactions may have important consequences on the reaction mechanism due to the separation of reactants, products and intermediates (physical or solubility effects). This paper focusses on a few selected examples of such effects from our research on reactions of or catalyzed by platinum metal complexes with the water soluble phosphines: m-sulfonatophenyldiphenylphosphine (TPPMS) and 1,3,5-triaza-7-phosphaadamantane (PTA).
Published Version
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