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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.

Keywords: Stannanes; Organotin compounds; Citrates; Propane-1,2,3-tricarboxylates; IR spectroscopy; NMR spectroscopy, ¹H, ¹³C and ¹¹⁹Sn; CP/MAS NMR spectroscopy, ¹³C and ¹¹⁹Sn; Mössbauer spectroscopy; Crystal structure.