Synthesis, solid-state and solution structures of bis{N,N′-bis[(2-thienyl)methylene]-1,2-diaminoethane}-silver(I) and -copper(I) trifluoromethanesulfonate complexes
Abstract
Reaction of 2 equivalents of the thienyl ketimines [(SC4H3)CRN]2C2H4(R = Me or SC4H3) with 1 equivalent of MI(O3SCF3)(M = Ag or Cu) resulted in formation of stable [M{[(SC4H3)CR
N]2-C2H4}2][O3SCF3] complexes. The crystal structures of [Ag{[(SC4H3)CMe
N]2C2H4}2][O3SCF3] and [Cu{[(SC4H3)C
N]2C2H4}2][O3SCF3] have been determined. Both unit cells contain discrete anions and, basically isostructural, complex cations. The co-ordination sphere of the metal(I) centre is dominated by four imine N atoms [Ag, 2.329(3); Cu, 2.014(14)–2.110(13)Å] provided by two symmetrically, bidentate co-ordinating [(SC4H3)CR
N]2C2H4 ligands. Four thiophene S atoms are also in proximity of the metal nucleus [Ag, 3.259(2); Cu, 3.160(8)–3.438(6)Å], but do not co-ordinate. The AgN4 geometry is flattened, as indicated by the spatial geometry of the four donor atoms, and tends more to square planar than to the usual tetrahedral arrangement. The CuN4 geometry is slightly compressed from tetrahedral. A characteristic of these complexes is their very low solubility which makes futher spectroscopic studies difficult. Various 1H NMR experiments have established that the complex cations are isostructural, having a tetrahedral co-ordination geometry similar to that found in the crystals, comprising symmetrically co-ordinating, bidentate ligands. There are no indications that the solution structure is compressed. The solution structure is only kinetically stable at low temperatures (⩽180 K); at more elevated temperatures ligand exchange occurs, which is rapid at ambient temperatures.