Preparation, molecular structure, and stereochemical properties of copper(II) complexes co-ordinated to (3S)- and (RS)-3-aminopiperidine: effect of ring size on stereochromism
Abstract
A series of copper(II) complexes co-ordinated to a chiral heterocyclic diamine 3-aminopiperidine (apip) has been prepared. The complexes obtained from the racemic and optically active forms of apip with BF4– or ClO4– as the counter anions differ significantly in their spectroscopic properties. Such differences are discussed in comparison with those observed in the related copper(II) complexes of 3-aminohexahydroazepine. Mixed-anion complexes Cu(apip)2X(ClO4) have been prepared, and the X-ray crystallographic analysis of [Cu(NCS)(S-apip)2][ClO4] revealed that the thiocyanate occupies the fifth co-ordination site yielding a complex having square-pyramidal geometry. The anion dependency of the reflectance spectra revealed that the spectral change in the apip complexes is caused by steric rather than electronic effects of the anion.