Infrared, 119Sn, 13C and 1H NMR, 119Sn and 13C CP/MAS NMR and Mössbauer Spectral Study of Some Tributylstannyl Citrates and Propane-1,2,3-tricarboxylates

Abstract

Six tributylstannyl citrates and three tributylstannyl propane-1,2,3-tricarboxylates of the formula R1C(CH2COOR2)(COOR3)(CH2COOR4) (R1 = OH or H, R2, R3, R4 = H, Bu3Sn, C6H11NH3, (C6H11)2NH2 or (CH2)5NH2) have been synthesised, and their solution and solid-state structures studied by infrared, 1H, 13C and 119Sn NMR, 13C and 119Sn CP/MAS NMR and 119Sn Mössbauer spectroscopies. In non-coordinating solvents, the compounds exist as isolated molecules or ionic-pairs with their tin atoms in pseudotetrahedral environments. In coordinating solvents, the tin atoms in the compounds are five-coordinate owing to the participation of the solvent in bonding; and their trans-trigonal bipyramidal coordination spheres consist of the ipso-carbon atoms of the butyl substituents in equatorial plane, and the solvent molecule and the oxygen atom of the monodentate carboxyl group in axial positions. A part of tributylstannyl groups together with some bidentate bridging carboxylate groups form polymeric chains in the solid state of citrates and propane-1,2,3-tricarboxylates. Also dioxastanna-rings with the participation α-hydroxycarboxylate fragments and one of the tributylstannyl groups occur probably in some citrates in the solid state. The spectroscopic assignment for the citrate has been confirmed by crystal structure analysis.