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 NiII, CuII, ZnII, and CdII 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 [MII(HL)]3+, [MII(HL)2]4+, and [MII(HL)L]3+, indicative of a bidentate coordination mode of the ligand L. The UV/Vis spectra of the corresponding CuII complexes further confirmed bidentate coordination with trans‐CuN4 geometry. The overall stabilities of the bis complexes [ML2]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 (CuII and CoIII complexes) and confirmed by single‐crystal X‐ray diffraction studies of [Pt(Hcis‐dap)Cl4]Cl·H2O, [Pd(Hcis‐dap)2](ClO4)4·2H2O, and [Cu(Hcis‐dap)2(OH2)2](SO4)2·3.5H2O − 2x H+ + x Cu2+ 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](ClO4)2 and [Cu(3R‐ampy)(3S‐ampy)](ClO4)2, respectively. The crystal structure determination of [Co(cis‐dap)(tach)][ZnCl4]Cl·C2H5OH (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.

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{{Explor lien
   |wiki=    Sante
   |area=    H2N2V1
   |flux=    Main
   |étape=   Exploration
   |type=    RBID
   |clé=     ISTEX:51404FB7819F20C24A4E13660F2DA22C11C8E60E
   |texte=   The Coordination Chemistry of cis‐3,4‐Diaminopyrrolidine and Related Polyamines
}}