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 ) ([Sn 2 ( m BDCA-5t)] 2-, 1) and lead( II ) ([Pb₂(mBDCA-5t)]²-, 2) complexes have been prepared by hexadeprotonation of hexacarboxamide cryptand m BDCA-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 m -E and bridging m -E 5 ligands where E ¼ S or Se, and the Sn( II ) centers have both been oxidized to Sn( IV ). Solution and solid-state UV-Vis spectra of [( m -S 5 )Sn 2 ( m -S)( m BDCA-5t)] 2 ( 4 ) indicate that the complex acts reversibly as a source of S 3 c in DMF solution with a K eq ¼ 0.012 0.002. Reductive removal of all six chalcogen atoms is achieved through treatment of [( m -E 5 )Sn 2 ( m -E)( m BDCA- 5t)] 2 with PR 3 (R ¼ 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.