Structural characterization of triorganotin(IV) complexes with sodium fusidate and DFT calculations

Three new complexes of the steroid sodium fusidate (sodium 2-[(1S,2S,5R,6S,7S,10S,11S,13S,14Z,15R,17R)-13-(acetyloxy)-5,17-dihydroxy-2,6,10,11-tetramethyl tetracyclo[8.7.0.02,7.011,15] heptadecan-14-ylidene]-6-methylhept-5-enoate = (NaFusidate, NaFA)]), with triorganotin(IV) moieties have beenprepared and investigated by conventional techniques as FTIR, Mössbauer, ESI-MS and NMR spectroscopy.The isolated compounds showed stoichiometries organotin(IV)/fusidate 1/1, R3Sn(IV)FA (R = Me,FA1; Bu, FA2; Ph, FA3). The ligand coordination sites were determined by FTIR spectroscopic measurements.In the complexes, the carboxylate group of the fusidate ligand behaves as monodentate monoanionicdonor, binding the Sn(IV) through one oxygen atom.On the basis of C–Sn–OCOO angles, calculated through the rationalization of the 119Sn Mössbauerparameter nuclear quadrupole splitting, it has been confirmed that, in all the solid state complexes,the Sn(IV) was tetracoordinated in a distorted tetrahedral structure.Further data from 119Sn CP-MAS spectra confirmed the distorted tetrahedral arrangement.In MeOH solution, 1H, 13C and 119Sn NMR spectroscopy showed monomeric complexes, where the carboxylategroup mainly acts as monodentate ester-type ligand, and the occurrence of a coordinated solventmolecule to the tin center, as validated by non-relativistic NMR DFT study.