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-Kα 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].