Metal complexes of some asymmetric diaminodiamide ligands—III1,2: Rates of conversion from octahedral to square planar complexes of Ni(II)

Dissociation of the two amide protons from complexes of asymmetric diaminodiamides with Ni(II) in aqueous solution occurs under moderately basic conditions. The loss of the protons is accompanied by a conversion of the complex from octahedral to square planar. The rates of conversion for complexes NiL²⁺ were measured spectrophotometrically and were found to depend linearly on OH^?]. The diaminodiamide ligands used were S, R, S- and S, S, S-N, N′-dialanylpropylenediamine (DAPN), S, S-N, N′-dialanylethylenediamine (DAEN), R-N, N′-diglycylpropylenediamine (DGPN), and N, N′-diglycylethylenediamine (DGEN). The rates varied in the order SS-DAEN > DGEN > SRS-DAPN > R-DGPN ≈ SSS-DAPN.