Conformational trends in arsocane dithiophosphinates X(CH2CH2S)2AsS2PR2(X = O or S; R = Me, Et or Ph)

Abstract

Six arsocane diorganodithiophosphinates X(CH₂CH₂S)₂AsS₂PR₂(X = O or S; R = Me, Et or Ph) have been prepared in CH₂Cl₂ or benzene from X(CH₂CH₂S)₂AsCl (X = O or S) and the corresponding sodium or ammonium dithiophosphinates. The compounds were characterised by IR, mass and ¹H, ¹³C and ³¹P NMR spectroscopy. The single-crystal structures of O(CH₂CH₂S)₂AsS₂PPh₂ and S(CH₂CH₂S)₂AsS₂PPh₂ were determined. Both show an endocyclic, transannular As ⋯ X interaction and an exocyclic As ⋯ S secondary interaction. The co-ordination geometry can be described as trigonal bipyramidal with a face-capping intramolecular As ⋯ S secondary bonding. The oxa derivative is the first example of an arsocane of the type X(CH₂CH₂S)₂AsY with a chair–chair conformation, while the thia derivative, as with other thiaarsocanes, shows a boat–chair conformation.