The dihedral angle in the phenoxarsine system. The structure of two planar phenoxarsin-10-yl-dialkyldithiophosphinates and their relation with the secondary interactions

The crystal and molecular structures of two phenoxarsin-10-yl dithiophosphinates, O(C6H4)2AsS2PR2 (R?Me, Et), have been determined. The first compound O(C6H4)2AsS2PMe2 (1) is monoclinic, space group and Z = 4, with monomeric character and does not exhibit either intra- or intermolecular secondary interactions. The phenoxarsine moiety is closely planar (dihedral angle of 176.1) and the dithiophosphinate ligand acts as monodentate. The second compound, O(C6H4)2AsS2PEt2 (2), is triclinic, space group and Z = 2. It exhibits a dimeric, quasi-tricyclic structure based upon intra- and intermolecular AsS secondary bonds. The phenoxarsine moiety is also closely planar with a dihedral angle of 173.1 and the dithio ligand is aniso-bidentate. In these compounds, there is no evidence of any relationship between the value of the dihedral angle in the phenoxarsine derivatives and the presence of secondary interactions.