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RESEARCH PRODUCT

A119Sn Mössbauer spectroscopic study on complexes of di-and tri-organotin(IV) moieties with 2-mercaptoethanesulfonates, in the solid state and in aqueous solution

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The configuration of the bonding environment of tin in the complexes [R2Sn(SCH2CH2SO3)2]2− (R = Me, Ph) and [Me3Sn(SCH2CH2SO3)]− has been determined to be tetrahedral both in the solid state and in aqueous solution (for the methyl derivatives). The coordination number of tin increases to five in aqueous solutions for the Me2Sn(IV) complexes in Hepes buffer (N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid; at least in fivefold excess, at pH 7.4) due to coordination by the tertiary amino nitrogen atom. No effect is detected due to the surfactant 2-hydroxypropylcellulose concerning both coordination to tin and influence on the Mossbauer parameters. The stoichiometry of mixed complex formation in aqueous solution of Me2Sn(IV), 2-mercaptoethanesulfonate and Hepes is 1:2:1, according to a procedure of ‘Mossbauer titration’. All complexes in aqueous solution undergo slow lysis of the tin-sulfur bonds. Structural assignments have been generally effected on the basis of the magnitude of experimental values of Mossbauer nuclear quadrupole splittings, measured at 77 K for both solid and frozen aqueous absorbers, and comparison with data calculated by the point-charge model approach.