THE SKELETAL VIBRATIONAL-SPECTRA AND METAL-LIGAND FORCE-CONSTANTS OF COBALT(III) AMMINE COMPLEXES

Vibrational spectra of cobalt(III) hexammine, aquopentammine, chlorope ntammine, hydroxopentammine and cis-diaquotetrammine and their deutera ted complexes have been investigated by near-infrared-Fourier transfor m-Raman and IR spectroscopy in the solid state. Raman spectra of some aqueous solutions have also been recorded. Observed frequencies of the complexes have been assigned in the skeletal vibrational region from 200 to 600 cm. The spectra indicate that the cobalt(III) monoaquo- and diaquo-coordinated ammine complexes both have structural symmetries v ery similar to the hexammine octahedral complex. This is supported by a space group determination for the monoaquo complex by X-ray powder d iffraction. The skeletal symmetry force constants of the cobalt(III) a mmine complexes have been calculated from the observed Raman and IR da ta. The calculated frequencies of the complexes agree well with the ob served results. The general valence force field (GVFF) stretching forc e constants of cobalt(III)-oxygen, cobalt(Ill)-nitrogen and cobalt(III )-chlorine bonds have been determined from the calculation.