The coordination chemistry of cis-3,5-diaminopiperidine and substituted derivatives

Jörg W. Pauly, Jürgen Sander, Dirk Kuppert, Manuela Winter, Guido J. Reiss, Fabio Zürcher, Rudolf Hoffmann, Thomas F. Fässler, Kaspar Hegetschweiler

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An efficient and convenient method for the preparation of cis-3,5-diaminopiperidine (dapi) has been established and the coordination chemistry of this ligand with Co(II). Co(III), Ni(II), Cu(II), Zn(II), and Cd(II) has been investigated in the solid state and in aqueous solution. Potentiometric measurements revealed a generally high stability for the bis complexes of the divalent cations with maximum stability for Ni(II) (logβ2 = 21.2,β2 = [M(dapi)2][M]-1[dapi]-2, 25°C, μ = 0.1 mol dm-3). Cyclic voltammetry established quasi-reversible formation of [Ni(dapi)2]3+ with a redox potential of 0.91V (versus NHE) for the Ni(II/III) couple. [Co(dapi)2]3+ was prepared by aerial oxidation of the corresponding Co(II) precursor. The two isomers trans-[Co(dapi)2]3+ (13+, 26%) and cis-[Co(dapi)2]3+ (23+, 74%), have been separated and isolated as solid C1- and CF3SO3- salts. In a non-aqueous medium 13+ and 23+ reacted with paraformaldehyde and NEt3 to give the methylidene-imino derivatives 33+ and 43+, in which the two piperidine rings are bridged by two or one N-CH2-O-CH2 N bridges, respectively. Crystal structure analyses were performed for H3da-pi[ZnCl4]Cl, 1CI3·2H2O, 2Cl3·H2O, 3[ZnCl4]Cl, 4[ZnCl4]Cl, [Ni(dapi)2]Cl2. H2O, [Cu(dapi)2](NO3)2, [Cu(dapi)Cl2], [(dapi)ClCd-(μ2-Cl)2-CdCl(dapi)], and [Co(dapi)(NO2)(CO3)]. The stability of [M(II)(dapi)]2+ and [M(II)(dapi)2]2+ complexes in aqueous solution, particularly the remarkably high tendency of [M(dapi)]2+ to undergo coordinative disproportionation is discussed in terms of the specific steric requirements of this ligand. Molecular mechanics calculations have been performed to analyze the different types of strain in these complexes. A variety of alkylated derivatives of dapi have been prepared by reductive alkylation with formaldehyde, benzaldehyde, salicylaldehyde, and pyridine-2-carbaldehyde. The Ni11 complexes of the pentadentate N3,N5-bis-(2-pyridinylmethyl)-cis-3,5-diaminopiperidine (py2dapi) and the hexadentate N3,N5,1-tris(2-pyridinylmethyl)-cis-3,5-diaminopiperidine (py3dapi) have been isolated as crystalline ClO4- salts [Ni-(py2dapi)Cl]ClO4 and [Ni(py3dapi)]-(ClO4)2· H2O and characterized by crystal structure analyses.

Original languageEnglish
Pages (from-to)2830-2846
Number of pages17
JournalChemistry - A European Journal
Issue number15
StatePublished - 4 Aug 2000
Externally publishedYes


  • N ligands
  • Polyamines
  • Stability constants
  • Structure elucidation


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