Spectroscopic Studies of Poly nuclear Complexes. I. Preparations and Circular Dichroisms of Tetrakis(l-propylenediamine)-dicobalt(III) Complexes Containing μ-Amido Group

Abstract

Abstract New binuclear cobalt(III) complexes, (−)D-[(l-pn)2Co(μ-NH2,O2)Co(l-pn)2](NO3)4·3H2O, (+)D-[(l-pn)2Co(μ-NH2,O2)Co(l-pn)2]I3·6H2O, (+)D-[(l-pn)2Co(μ-NH2,NO2)Co(l-pn)2]Br4·6H2O, (+)D-[(l-pn)2Co(μ-NH2,OH)Co(l.pn)2](NO3)4·2H2O and (−)D-[(l-pn)2Co(μ-NH2,SO4)Co-(l-pn)2](NO3)3 were prepared and their absolute configurations determined to be ΛΛ on the consideration of the stereospecific coordination of l-propylenediamine (l-pn) to the metal ion. On the basis of these identifications, absolute configurations of the corresponding ethylenediamine-(en) complex ions were assigned. The nature of the d–d bands of these polynuclear complexes seems to be very similar to those of uninuclear cobalt(III) complexes. One of the two central cobalt(III) ions is regarded as a member of an asymmetric chelate ligand to the other cobalt ion, and the CD corresponding to the d–d bands appears to depend mainly on the strength of vicinal effect due to such a chelate ring.