Multi-electron reactivity of a cofacial di-tin(I) cryptand: partial reduction of sulfur and selenium and reversible generation of S[subscript 3][superscript ˙−]

Abstract

Cofacial bimetallic tin(ii) ([Sn[subscript 2](mBDCA-5t)][superscript 2−], 1) and lead(ii) ([Pb[subscript 2](mBDCA-5t)][superscrip 2−], 2) complexes have been prepared by hexadeprotonation of hexacarboxamide cryptand mBDCA-5t-H[subscript 6] 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-E[subscript 5] 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-S[subscript 5])Sn[subscript 2](μ-S)(mBDCA-5t)][superscript 2−] (4) indicate that the complex acts reversibly as a source of S[subscript 3][superscript −] in DMF solution with a K[subscript eq] = 0.012 ± 0.002. Reductive removal of all six chalcogen atoms is achieved through treatment of [(μ-E[subscript 5])Sn[subscript 2](μ-E)(mBDCA-5t)][superscript 2−] with PR[subscript 3] (R =[superscript t]Bu, Ph, O[superscript i] Pr) to produce six equiv. of the corresponding EPR[subscript 3] compound with regeneration of di-tin(ii) cryptand complex 1.