Organometallic Complexes with Biological Molecules, VI. Diorganotin(IV) and Triorganotin(IV) Ampicillin and Methicillin Derivatives: Spectroscopic Investigations in the Solid State

Derivatives of D (‐)–α‐aminobenzylpenicillin (ampicillin) and of 2,6‐dimethoxyphenylpenicillin (methicillin) with diorgano‐ and triorgano‐tin(IV) moieties have been synthesized. The stoichiometries of the compounds obtained were of the type R 2 SnClL·H 2 O, R 3 SnClL·H 2 O [L=ampicillin or methicillin monoanion; R=Me, Bu, Ph] and R 2 Snampic 2 · 2H 2 O (ampic=ampicillin; R=Me, Bu, Ph). For R 2 SnClL·H 2 O and R 3 SnClL Na· ‐ H 2 O, infrared (IR) data suggest five‐coordination around the tin(IV) atom; in R 2 Snampic 2 · 2H 2 O six‐coordination is most likely to occur. Thermogravimetric (TG) analysis excludes any involvement in the coordination of tin(IV) by water molecules, in any of the compounds. Trigonal bipyramidal configurations in the solid state are proposed for both R 2 SnClL·H 2 O and R 3 SnClL Na·H 2 O (L=ampicillin or methicillin) on the basis of the above‐mentioned IR and Mössbauer data. As far as R 2 Snampic 2 ·2H 2 O compounds are concerned, the coordination geometry at tin could be, as previously reported for analogous R 2 Snamox 2 .2H 2 O derivatives, skew‐trapezoidal bipyramidal, the monoanionic bidentate chelating ampicillin residue being in the trapezoidal plane and having bent axial organic groups. Electronegativity equalization procedures have been applied to idealized trigonal bipyramidal structures for R 2 SnClL·H 2 O and R 3 SnClL Na·H 2 O (L=ampicillin or methicillin) and to octahedral trans ‐R 2 for R 2 Snampic 2 ·2H 2 O, to estimate the partial atomic charges on the tin atoms, Q   s   n, which have been correlated with the isomer shift (δ) Mössbauer parameter.