Mono- and Dinuclear Complexes of a Flexible Schiff Base Ligand − Crystal Structures of a Bishelicate and Two Acentric Monohelicates

Neutral NiII, PdII, CuII, AgI, ZnII, CdII, and PbII complexes of N,N′‐bis(2‐tosylaminobenzylidene)‐1,4‐diaminobutane (H2SB) have been prepared. The Schiff base seems to exist in a helically coiled state around nickel, copper and zinc ions, but not in Pd(SB)·3H2O·MeCN, Ag2(SB)·2H2O, Cd(SB)·3H2O, and Pb(SB)·3H2O, the metal ions of which seem to show planar geometries. The determination of the absolute structures of Cu(SB)·MeCN and Zn(SB)·2MeCN, which crystallise as non‐centrosymmetric racemic compounds, shows that these metal(II) ions assume distorted tetrahedral coordination geometries involving the four N atoms of the dianionic ligand. X‐ray structural characterisation also shows that this ligand behaves as a N2+N2 donor in the [4+4] bishelicate Ni2(SB)2·5MeCN. Secondary interactions between metal centres and one of the O atoms of each tosyl group are detected in these three crystal structures, being especially intense in the dimeric one. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)