Structure, Stability, and Redox Properties of MnII, FeII, CoII, and CoIII Complexes with 1,3,5-Triamino-1,3,5-trideoxy-cis-inositol

Michele Ghisletta, Lorenza Hausherr-Primo, Krisztina Gajda-Schrantz, Gábor Machula, László Nagy, Helmut W. Schmalle, Greti Rihs, Frank Endres, Kaspar Hegetschweiler

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Abstract

The interaction of MnII, FeII, and CoII with the ligand taci (=1,3,5-triamino-1,3,5-trideoxy-cis-inositol) was studied in the solid state and in aqueous solution. Magnetic susceptibility measurements revealed a high-spin electron configuration for the Mn and the Fe complexes. Crystal data: [Mn(taci)2](NO3)2·2H2O (1), C12H34MnN3O14, monoclinic, space group P21/c, a = 7.107(5) Å, b = 8.742(2) Å, c = 18.527(6) Å, β= 100.20(4)°, Z = 2; [Fe(taci)2]Cl2·6H2O (2), C12Cl2FeH42N6O12, monoclinic, space group C2/m, a = 11.420(2) Å, b = 9.300(2) Å, c = 13.330(3) Å, β = 111.97(3)°, Z = 2; [Co(taci)2](NO3)2·1.5H2O (3), C12CoH33N8O13.5, monoclinic, space group P21/c, a = 7.081(1) Å, b = 8.743(1) Å, c = 18.181(2) Å, β= 99.49(1)°, Z = 2. All three structures exhibited distorted octahedral MN6 coordination. The stability constants for the complexes [M(taci)]2+ (M = Mn, Fe, Co) and [M(taci)2]2+ (M = Fe, Co) in aqueous media have been evaluated by potentiometric titration. Comparison with other divalent cations showed that the order of stability increases MnII < CdII ≈ FeII < ZnII < CoII < CuII < NiII. In alkaline aqueous media, the complexes 1-3 are readily oxidized by dioxygen. The redox properties were analyzed by a series of polarographic and cyclic voltammetric measurements. A new isomeric form of a bis-taci CoIII complex was formed, where one of the taci ligands coordinates the metal cation by one nitrogen and two oxygen atoms. The complex was isolated in crystalline form as [Co(taci)(Htaci)](NO3)4·0.5H2O (4), C12-CoH32N32O18O18.5, monoclinic, space group C2/c, a = 30.541(3) A, b = 9.015(1) Å, c = 17.852(2) Å, β= 95.63(1)°, Z = 8. [Co(tach)(H2O)x(NO3)3-x] x+ (tach = all-cis-1,3,5-triaminocyclohexane, 0 ≤ x ≤ 3) was used as a model to demonstrate that, for CoIII, the substitution of the three monodentate coligands by a taci molecule resulted generally in an asymmetric binding. An N,O,O and an N,N,O coordination mode were observed for [Co(taci)(tach)](NO3)3·3H2O (5), and [Co(H-itaci)(tach)](NO3)2·(3 - x)H2O·MeOH, 0.2 ≤ x ≤ 0.5 (6), respectively. Crystal data: 5 (C12CoH36N9O15), monoclinic, P21/n, a = 8.942(5) Å, b = 30.07(3) Å, c = 9.354(5) Å, β= 109.25(4)°, Z = 4; 6 (x ≈ 0.2, C12CoH12.2N8O12), monoclinic, P21/n, a = 7.337(2) Å, b = 19.847(4) Å, c = 15.226(3) Å, β= 93.59(3)°, Z = 4.

Original languageEnglish
Pages (from-to)997-1008
Number of pages12
JournalInorganic Chemistry
Volume37
Issue number5
Publication statusPublished - Dec 1 1998

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

Ghisletta, M., Hausherr-Primo, L., Gajda-Schrantz, K., Machula, G., Nagy, L., Schmalle, H. W., Rihs, G., Endres, F., & Hegetschweiler, K. (1998). Structure, Stability, and Redox Properties of MnII, FeII, CoII, and CoIII Complexes with 1,3,5-Triamino-1,3,5-trideoxy-cis-inositol. Inorganic Chemistry, 37(5), 997-1008.