ORGANOMETALLIC COMPLEXES WITH BIOLOGICAL MOLECULES .6. DIORGANOTIN(IV) AND TRIORGANOTIN(IV) AMPICILLIN AND METHICILLIN DERIVATIVES - SPECTROSCOPIC INVESTIGATIONS IN THE SOLID-STATE

Derivatives of D(-)-alpha-aminobenzylpenicillin (ampicillin) and of 2, 6-dimethoxyphenylpenicillin (methicillin) with diorgano- and triorgano -tin(IV) moieties have been synthesized. The stoichiometries of the co mpounds obtained were of the type R(2)SnCIL . H2O, R(3)SnCILNa . H2O [ L=ampicillin or methicillin monoanion; R=Me, Bu, Ph] and R(2)Snampic(2 ) .2H2O (ampic=ampicillin; R=Me, Bu, Ph). For R(2)SnCIL . H2O and R(3) SnCILNaH(2)O, infrared (IR) data suggest five-coordination around the tin(IV) atom; in R(2)Snampic(2) .2H2O 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 compound s. Trigonal bipyramidal configurations in the solid state are proposed for both R(2)SnCIL . H2O and R(3)SnCILNa . H2O (L=ampicillin or methi cillin) on the basis of the above-mentioned IR and Mossbauer data. As far as R(2)Snampic(2) .2H2O compounds are concerned, the coordination geometry at tin could be, as previously reported for analogous R(2)Sna mox(2).2H(2)O derivatives, skew-trapezoidal bipyramidal, the monoanion ic bidentate chelating ampicillin residue being in the trapezoidal pla ne and having bent axial organic groups. Electronegativity equalizatio n procedures have been applied to idealized trigonal bipyramidal struc tures for R(2)SnCIL . H2O and R(3)SnCILNa . H2O (L=ampicillin or methi cillin) and to octahedral trans-R(2) for R(2)Snampic(2) .2H2O, to esti mate the partial atomic charges on the tin atoms, Q(sn), which have be en correlated with the isomer shift (delta) Mossbauer parameter.