Diorganotin(IV) complexes of D-galacturonic acid: solid-state and solution-phase structural study

Three diorganotin(IV) complexes of D-galacturonic acid (H(2)GalA; R = Me, n-Bu, Ph), two of which are new derivatives (R. = Me, Ph), have been synthesized and their solid-state and solution-phase investigated by IR, Mossbauer, H-1, C-13 and Sn-119 NMR spectroscopy. The FTIR data suggest that H(2)GalA, in the dialkyltin derivatives, behaves as a dianionic ligand, coordinating the tin(IV) atom through an ester-type carboxylate and deprotonated. alcoholic hydroxo groups, whereas a bridging carboxylate occurs in the diphenyltin(IV) complex. Octahedral and trigonal bipyramidal local geometries on tin(IV) atoms are proposed for dialkyltin(IV)GalA and diphenyltin(IV)GalA complexes respectively on the basis of Mossbauer spectroscopy. In D2O solution, R2Sn(IV) moieties seem to be mainly coordinated by the GalA(2-) in the beta-furanosidic (beta-GalfA(2-)) form, involving the beta-furanosidic ring in rotational equilibrium. However, the alpha-furanosidic (alpha-GalfA(2-)), alpha-pyranosidic (alpha-GalPA(2-)) and the beta-pyranosidic (beta-GalpA(2-)) isomers are also involved in the coordination upon the tin atom to a minor extent. In DMSO-d(6) solution, R2Sn(IV) moieties are coordinated almost entirely by the GalA(2-) in the beta-furanosidic form. Copyright (C) 2003 John Wiley Sons, Ltd.