摘要 : The new, tridentate, facially coordinating ligand 1,4-diazepan-6-amine (daza) has been prepared from ethane-1,2diamine and 2,3-dibromo-1-propanol in a seven-step procedure with an overall yield of 22%. The conformation of the free... 展开 The new, tridentate, facially coordinating ligand 1,4-diazepan-6-amine (daza) has been prepared from ethane-1,2diamine and 2,3-dibromo-1-propanol in a seven-step procedure with an overall yield of 22%. The conformation of the free ligand has been elucidated by pH- and temperature-dependent H-1 NMR spectroscopy and by a single-crystal Xray structure analysis of H(3)dazaCl(3)center dot H2O. A twisted chair with a predominantly equatorial orientation of the primary amino group has been established for daza and its protonation products H(x)daza(x+) (1 <= x <= 3). The formation constants of [M(daza)](2+) and [M(daza)(2)](2+) have been determined in aqueous solutions for M = Ni-II, Cu-II, Zn-II, Cd-II, and Co-II by potentiometric and spectrophotometric measurements, and a remarkably high stability has been found for the bis complexes ML2 in comparison to the mono complexes ML. This effect is discussed in terms of the particular steric requirements of the daza ligand. [Cu(daza)Cl-2], [Ni(daza)(2)]Cl(2)center dot 3.2H(2)O and [Zn(daza)(2)]SO(4)center dot 5H(2)O have been characterized by single-crystal X-ray analyses. Aerial oxidation of Co2+ in the presence of daza results in the formation of the inert [Co(daza)(2)](3+), which was isolated as a mixture of the cis and trans isomers. These two isomers were separated by chromatographic methods and identified by NMR spectroscopy and single-crystal X-ray structure analysis of cis-[Co(daza)(2)][ZnBr4]Br center dot H2O and trans-[Co(daza)(2)](3)[ZnBr4](2)-Br(5)center dot 4H(2)O. The redox potentials of [Ni(daza)(2)](3+/2+) (1.04 V vs. NHE) and [Co(daza)(2)](3+/2+) (-0.21 V vs. NHE) were determined by cyclic voltammetry. The values are slightly more positive than for corresponding complexes with related cyclic triamines. This effect is again discussed in terms of the particular steric requirements of these ligands. 收起