1992 Volume 8 Issue 1 Pages 63-66
The infrared (IR) spectra of isomers of dicyanobis(propylenediamine)chromium(III) chloride and related complexes have been measured over the range of 4000 to 290cm-1 in order to determine the characteristic frequencies available for identification of the isomers. Our results suggest that the desired distinctive frequencies exist mainly in the C=N stretching band at 2145-2131cm-1, the vibrations in the region 838-830cm-1, the Cr-N stretching vibrations in the region 590-431cm-1, and the Cr-C stretching or Cr-C≡N bending vibrations in the region 408-320cm-1. These frequencies have enabled: 1) a distinction between cis-(+)589-[Cr(CN)2(d-pn)(l-pn)]Cl and the diastereoisomeric isomers, such as cis-(-)589-[Cr(CN)2(d-pn)2]Cl or cis-(+)589-[Cr(CN)2(l-pn)2]Cl (pn=propylenediamine=1, 2-diaminopropane); 2) the identification of the geometric isomers of Λ-cis-(-)589-[Cr(CN)2(d-pn)2]Cl which results from differences in the relative position of the methyl groups of propylenediamine ligands, and 3) the discrimination of ethylenediamine complexes from that of propylenediamine. In these paramagnetic Cr(III) complexes, the measurement of NMR spectra is made worthless due to the influence of the large magnetic moment of unpaired electrons. Accordingly, the importance of the structural information obtained by IR measurements is very high in their identification.