6533b854fe1ef96bd12afc43

RESEARCH PRODUCT

A study of dimethyltin(IV)-L-cysteinate in aqueous solution

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The in vivo activity of some R2Sn-L-cysteinate complexes (R = Me, Et, n-Bu) against murine P-388 leukaemia has been tested. Only the Et2Sn(IV) complex showed a marginal positive effect. Trigonal bipyramidal tin environments with two carbon (R) atoms and the sulfur atom in the equatorial plane and oxygen (carboxylate) and nitrogen (NH2) in apical positions have been proposed for the solid compexes (R = Me, Et, n-Bu, Ph) on the basis of experimental Mossbauer parameters and infrared (IR) data. Aqueous solutions of the Me2SnL-cysteinate have been studied by IR, 1H NMR and 119Sn Mossbauer spectroscopy (in frozen solution) at different pH values to identify the Me2Sn(IV) species present. At pH > 2 the dimethyltin aquocation is complexed by the ionized sulfhydryl group of L-cysteine to form a five-coordinated species. With increasing pH values, NH3+ is deprotonated and a chelate is proposed with both the sulfhydryl and the amino group bonded to tin, one water molecule or (at still higher pH values) one hydroxyl ion occupying the fifth coordination site of a trigonal bipyramid around tin. Finally at pH > 10 the NH2 group is substituted by a hydroxyl ion.