Preparation and structural characterization of six new diorganotin(IV) complexes of the R2Sn(SaleanH2) and R2Sn(SalceanH2) type (R = Me, nBu, Ph)

Six new diorganotin(IV) complexes have been prepared from R2SnO (R = Me, Bu-n, Ph) and the Salan ligands SaleanH(4) (SaleanH(4) = N,N'-bis(o-hydroxybenzyl)-1,2-diaminoethane) and SalceanH(4) (SalceanH(4)=N,N'-bis(o-hydroxybenzyl)-1,2-diaminocyclohexane) in order to determine the preferred coordination mode of these ligands in dependence of their flexibility and basicity as well as the steric bulk of the organic groups attached to the tin(IV) atom. The present NMR spectroscopic and X-ray crystallographic study shows that the SaleanH(2) and SalceanH(2) ligands prefer a fac fac configuration when coordinated to a diorganotin(IV) fragment, in which the nitrogen atoms are located trans to the organic groups. Depending on the steric bulk of the organic substituents, the conformation of the coordinated ligand can vary with respect to the orientation of the benzyloxy phenyl rings. In the solution state there may exist a rapid equilibrium between these possible conformations. For related R2Sn(Salen) complexes so far only structures with trans configurations have been reported, however, for SalanH(2) complexes with other metal ions both examples with fac-fac and fac-mer configurations are known. In the solid state structure of one of the complexes studied in here an interesting C-H(...)pi intermolecular contact between a chloroform molecule and an aromatic ring has been detected. (C) 2002 Elsevier Science B.V. All rights reserved.