摘要 : cis-3,4-Diaminopyrrolidine (cis-dap), trans-3,4-diaminopyrrolidine (trans-dap), cis-1,2-cyclopentanediamine (cis-cptn), and trans-1,2-cyclopentanediamine (trans-cptn) have been prepared in multigram quantities. The complexation of... 展开 cis-3,4-Diaminopyrrolidine (cis-dap), trans-3,4-diaminopyrrolidine (trans-dap), cis-1,2-cyclopentanediamine (cis-cptn), and trans-1,2-cyclopentanediamine (trans-cptn) have been prepared in multigram quantities. The complexation of these ligands and of 3-aminopyrrolidine (ampy) with Ni~(II), Cu~(II), Zn~(II), and Cd~(II) has been studied in solution by means of potentiometric and spectrophotometric titrations. The complexes of the triamines cis-dap and trans-dap show a pronounced tendency to form protonated species such as [M~(II)(HL)]~(3+), [M~(II)(HL)_2]~(4+), and [M~(II)(HL)L]~(3+), indicative of a bidentate coordination mode of the ligand L. The UV/Vis spectra of the corresponding Cu~(II) complexes further confirmed bidentate coordination with trans-CuN_4 geometry. The overall stabilities of the bis complexes [ML_2]~(2+) decrease in the order cis-cptn > cis-dap > trans-cptn > ampy > trans-dap. The considerably lower stabilities of the ampy complexes as compared to the corresponding cis-dap complexes indicate metal binding to the two primary amino groups of the latter ligand. This was supported by molecular mechanics calculations (Cu~(II) and Co~(III) complexes) and confirmed by singlecrystal X-ray diffraction studies of [Pt(Hcis-dap)Cl_4]Cl·H_2O, [Pd(Hcis-dap)_2](ClO_4)_4·2H_2O, and [Cu(Hcis-dap)_2(OH_2)_2]-(SO_4)_2·3.5H_2O - 2x H~+ + x Cu~(2+) with 0.01 ≤ x ≤ 0.11. For the diamine ligands, coordination through the two exocyclic amino groups or through one exocyclic and one endocyclic amino group was established from the X-ray structure analyses of [Ni(cis-cptn)_2](ClO_4)_2 and [Cu(3R-ampy)(3S-ampy)]-(ClO_4)_2, respectively. The crystal structure determination of [Co(cis-dap)(tach)][ZnCl_4]Cl·C_2H_5OH (tach = cis-1,3,5-cyclohexanetriamine) revealed tridentate, facial coordination of cis-dap in this particular complex. However, the structural parameters of the [Co(cis-dap)(tach)]~(3+) moiety indicate significant strain for this coordination mode. The coordinating properties of the ligand cis-dap are compared with those of other aliphatic and alicyclic triamines. 收起