Facile, ambient temperature, double Sn-C bond cleavage: synthesis, structure, and electrochemistry of organotin and organotellurium ferrocenecarboxylates

Abstract

The reaction of organotin halides R₃SnCl (R = Me or benzyl) with ferrocenecarboxylic acid (FcCOOH) in the presence of triethylamine affords Me₃SnO₂CFc (1) or Bn₃SnO₂CFc (2) (Bn = benzyl). The latter undergoes a facile ambient temperature double Sn-C bond cleavage to give the monoorganostannoxane, [BnSn(O)O₂CFc]₆ (3). Compound 3 is also formed by a single Sn-C bond cleavage reaction in the reaction between Bn₂SnCl₂ and FcCOOH. In contrast, the reaction of Me₂SnCl₂ with FcCOOH affords Me₂Sn(O₂CFc)₂ (4), where the Sn-C bonds are robust. Organotellurium ferrocene carboxylates [(4-OMe-Ph)₂Te(O₂CFc)₂] (5) and [(4-NMe₂-Ph)₂Te(O₂CFc)₂] (6) are obtained in the reaction of the corresponding diorganotellurium oxides/halides with FcCOOH. Whereas 1 is a zig-zag one-dimensional coordination polymer with a square-wave architecture, the structures of 3-6 are molecular. Compound 3 is a hexameric cage and possesses a drum-type structure, whereas 4 is mononuclear and contains a six-coordinate tin with a skewed trapezoidal geometry. In compounds 5 and 6 the lone pairs on tellurium are stereochemically active thereby conferring see-saw geometries. Compounds 1, 2, 4, and 5 show single quasireversible peaks at +0.62, +0.72, +0.66, and +0.64 V, respectively with respect to the Ag/AgCl electrode. Compound 3, which contains six ferrocene arms, shows a single redox event along with a stripping peak. Compound 6 shows quasireversible and irreversible redox events at +0.62 and +1.17 V, respectively. The latter is due to a ligand-centered oxidation.