Multi-electron reactivity of a cofacial di-tin(ii) cryptand: partial reduction of sulfur and selenium and reversible generation of S(3)˙(–)

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