Multi-electron reactivity of a cofacial di-tin(ii) cryptand: partial reduction of sulfur and selenium and reversible generation of S3˙−

Abstract

Cofacial bimetallic tin(II) ([Sn₂(mBDCA-5t)]²⁻, 1) and lead(II) ([Pb₂(mBDCA-5t)]²⁻, 2) complexes have been prepared by hexadeprotonation of hexacarboxamide cryptand mBDCA-5t-H₆ together with double Sn(II) or Pb(II) insertion. Reaction of 1 with elemental sulfur or selenium generates di-tin polychalcogenide complexes containing μ-E and bridging μ-E₅ ligands where E = S or Se, and the Sn(II) centers have both been oxidized to Sn(IV). Solution and solid-state UV-Vis spectra of [(μ-S₅)Sn₂(μ-S)(mBDCA-5t)]²⁻ (4) indicate that the complex acts reversibly as a source of S₃˙⁻ in DMF solution with a K_eq = 0.012 ± 0.002. Reductive removal of all six chalcogen atoms is achieved through treatment of [(μ-E₅)Sn₂(μ-E)(mBDCA-5t)]²⁻ with PR₃ (R = ^tBu, Ph, OⁱPr) to produce six equiv. of the corresponding EPR₃ compound with regeneration of di-tin(II) cryptand complex 1.