Zinc(II) bis(O,O′-dialkyl dithiophosphates): interaction with small nitrogen bases. The crystal and molecular structure of hexakis(µ-O,O′-diethyl dithiophosphato)-µ4-thio-tetrazinc, Zn4[S2P(OEt)2]6S

Abstract

In the presence of atmospheric moisture, triethylamine, diethylamine, and 1,5-diazabicyclo[4.3.0] non5-ene promote the hydrolysis of zinc(II) bis(O,O′-dialkyl dithiophosphates), Zn[S₂P(OR)₂]₂(R = Et or Prⁱ), to the corresponding hexakis(O,O′-dialkyl dithiophosphato)-µ₄-oxo-tetrazinc derivatives, Zn₄[S₂P(OR)₂]₆O. Under anhydrous conditions, however, the complexes Zn[S₂P(OEt)₂]₂·2.75NHEt₂ and Zn[S₂P(OPrⁱ)₂]₂·nNEt₃(n= 1 or 2.75) are obtained. The crystal and molecular structure of hexakis(O,O′-diethyl dithiophosphato)-µ₄-thio-tetrazinc, Zn₄[S₂P(OEt)₂]₆S, a by-product in the synthesis of Zn[S₂P(OEt)₂]₂, is also reported. Crystals are trigonal, space group R3 (no. 146), with a= 20.776(2), c= 11.560(2)Å, and Z= 3. The structure determination was carried out by the heavy-atom method using Mo-K_α radiation (λ= 0.7107 Å) from 1 455 independent reflections with l > 3σ(I). The structure comprises independent, non-interacting molecules of composition Zn₄[S₂P(OEt)₂]₆S, which possess crystallographically-imposed three-fold symmetry. The three-fold axis is collinear with the unique Zn–S bond of the central Zn₄S core, which possesses nearly perfect tetrahedral symmetry [Zn–S 2.264(6)Å, 2.267(2)Å]. Each of the zinc-zinc axes of the tetrahedron is bridged almost symmetrically by the dithiophosphato ligands at somewhat longer zinc-sulphurdistances [ligand 1, 2.341 (4), 2.353(4); ligand 2, 2.335(3), 2.337(3)Å].