Preparation and Properties of Cobalt(III)–1,2-Bis(dimethylphosphino)ethane (dmpe) Complexes of the [Co(L)(dmpe)2]n+ Type

Abstract

Abstract Seven new cobalt(III)–phosphine complexes of the type [Co(L)(dmpe)2]n+ were prepared from trans-[Co(Cl or Br)2(dmpe)2]+, where dmpe denotes (CH3)2PCH2CH2P(CH3)2, and L is C2O42−, NH2CH2COO−(gly), NH2CH(CH3)COO−(ala), (C2H5)2NCS2−(dtc), (NCS−)2, (NCO−)2, or (CN−)2. Reactions of cis-[CoCl2(dmpe)2]+ with X− (X−=CN−, NCS−, and NCO−) yielded only trans-[CoX2(dmpe)2]+. Qualitative stabilities of the complexes containing a bidentate ligand in aqueous solution were found to decrease in the order L=CH(CH3CO)2−(acac), C2O42−, dtc>CO32−>>gly, ala>NH2CH2CH2NH2(en); the complexes containing O or S donor atoms are thermally more stable than those containing an amino donor group. The d–d absorption bands of the complexes were assigned by comparing the spectra with those of related Co(III)–phosphine and -en complexes. The IR and visible absorption spectra of the NCS− and NCO− complexes indicate an N coordination mode of these ambidentate ligands.