Stereoselective Coordination to Chiral Matrices. Cobalt(III). Chemistry of Simple Facially Coordinating Chiral Triamines

Peter Comba, Aldo Hörmann, Lisandra L. Martin, Luc Zipper

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9 Citations (Scopus)

Abstract

Chiral ligands coordinated to metal ions exert a selectivity towards the additional coordination of racemic substrates. Experimentally determined equilibria distributions of [Co(L3)2]3+ and [Co(L3)(L2)(X)]n+ are compared with calculated data based on strain‐energy minimization (L3: trap = propane‐1,2,3‐triamine; 1,2,4‐trab = butane‐1,2,4‐triamine; 1,2,3‐trab = butane‐1,2,3‐triamine; 1,3,4‐trpe = pentane‐1,3,4‐triamine; 1,3,4‐tmeb = 2‐methylbutane‐1,3,4‐triamine; 1,2,4‐trpe = pentane‐1,2,4‐triamine; L2: en = ethane‐1,2‐diamine; pn = propane‐1,2‐diamine; X: NH3, OH2, OH). Equilibration of Co(III) complexes was achieved by oxygenation of aqueous solutions of Co(II) salts in presence of the ligands. Quantitative isomer distribution was investigated with HPLC, and quantitative analysis of the enantiomeric excess (ee) of the racemic substrate (present in a two‐fold excess) was studied, after chromatographical recovery, by 1H‐NMR analysis of its Mosher‐acid derivative. There is good agreement between calculated and experimental data. Systems with L = 1,2,4‐trab are, as expected, relatively poorly discriminating (ee([Co(1,2,4‐trab)2]3+) ∼ 5%; ee([Co(1,2,4‐trab)(pn)(X)]n+) ∼ 10%). Calculations indicate that Me substitution of the ligand backbone of 1,2,4‐trab (and trap) leads to an increased enantioselectivity (with practically constant isomer selectivity), and at the optimum site for substitution ∼ 90% ee is predicted.

Original languageEnglish
Pages (from-to)874-882
Number of pages9
JournalHelvetica Chimica Acta
Volume73
Issue number4
DOIs
Publication statusPublished - 1 Jan 1990
Externally publishedYes

Cite this

@article{15f972520a594e709e27eb2b5df98aa8,
title = "Stereoselective Coordination to Chiral Matrices. Cobalt(III). Chemistry of Simple Facially Coordinating Chiral Triamines",
abstract = "Chiral ligands coordinated to metal ions exert a selectivity towards the additional coordination of racemic substrates. Experimentally determined equilibria distributions of [Co(L3)2]3+ and [Co(L3)(L2)(X)]n+ are compared with calculated data based on strain‐energy minimization (L3: trap = propane‐1,2,3‐triamine; 1,2,4‐trab = butane‐1,2,4‐triamine; 1,2,3‐trab = butane‐1,2,3‐triamine; 1,3,4‐trpe = pentane‐1,3,4‐triamine; 1,3,4‐tmeb = 2‐methylbutane‐1,3,4‐triamine; 1,2,4‐trpe = pentane‐1,2,4‐triamine; L2: en = ethane‐1,2‐diamine; pn = propane‐1,2‐diamine; X: NH3, OH2, OH−). Equilibration of Co(III) complexes was achieved by oxygenation of aqueous solutions of Co(II) salts in presence of the ligands. Quantitative isomer distribution was investigated with HPLC, and quantitative analysis of the enantiomeric excess (ee) of the racemic substrate (present in a two‐fold excess) was studied, after chromatographical recovery, by 1H‐NMR analysis of its Mosher‐acid derivative. There is good agreement between calculated and experimental data. Systems with L = 1,2,4‐trab are, as expected, relatively poorly discriminating (ee([Co(1,2,4‐trab)2]3+) ∼ 5{\%}; ee([Co(1,2,4‐trab)(pn)(X)]n+) ∼ 10{\%}). Calculations indicate that Me substitution of the ligand backbone of 1,2,4‐trab (and trap) leads to an increased enantioselectivity (with practically constant isomer selectivity), and at the optimum site for substitution ∼ 90{\%} ee is predicted.",
author = "Peter Comba and Aldo H{\"o}rmann and Martin, {Lisandra L.} and Luc Zipper",
year = "1990",
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Stereoselective Coordination to Chiral Matrices. Cobalt(III). Chemistry of Simple Facially Coordinating Chiral Triamines. / Comba, Peter; Hörmann, Aldo; Martin, Lisandra L.; Zipper, Luc.

In: Helvetica Chimica Acta, Vol. 73, No. 4, 01.01.1990, p. 874-882.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Stereoselective Coordination to Chiral Matrices. Cobalt(III). Chemistry of Simple Facially Coordinating Chiral Triamines

AU - Comba, Peter

AU - Hörmann, Aldo

AU - Martin, Lisandra L.

AU - Zipper, Luc

PY - 1990/1/1

Y1 - 1990/1/1

N2 - Chiral ligands coordinated to metal ions exert a selectivity towards the additional coordination of racemic substrates. Experimentally determined equilibria distributions of [Co(L3)2]3+ and [Co(L3)(L2)(X)]n+ are compared with calculated data based on strain‐energy minimization (L3: trap = propane‐1,2,3‐triamine; 1,2,4‐trab = butane‐1,2,4‐triamine; 1,2,3‐trab = butane‐1,2,3‐triamine; 1,3,4‐trpe = pentane‐1,3,4‐triamine; 1,3,4‐tmeb = 2‐methylbutane‐1,3,4‐triamine; 1,2,4‐trpe = pentane‐1,2,4‐triamine; L2: en = ethane‐1,2‐diamine; pn = propane‐1,2‐diamine; X: NH3, OH2, OH−). Equilibration of Co(III) complexes was achieved by oxygenation of aqueous solutions of Co(II) salts in presence of the ligands. Quantitative isomer distribution was investigated with HPLC, and quantitative analysis of the enantiomeric excess (ee) of the racemic substrate (present in a two‐fold excess) was studied, after chromatographical recovery, by 1H‐NMR analysis of its Mosher‐acid derivative. There is good agreement between calculated and experimental data. Systems with L = 1,2,4‐trab are, as expected, relatively poorly discriminating (ee([Co(1,2,4‐trab)2]3+) ∼ 5%; ee([Co(1,2,4‐trab)(pn)(X)]n+) ∼ 10%). Calculations indicate that Me substitution of the ligand backbone of 1,2,4‐trab (and trap) leads to an increased enantioselectivity (with practically constant isomer selectivity), and at the optimum site for substitution ∼ 90% ee is predicted.

AB - Chiral ligands coordinated to metal ions exert a selectivity towards the additional coordination of racemic substrates. Experimentally determined equilibria distributions of [Co(L3)2]3+ and [Co(L3)(L2)(X)]n+ are compared with calculated data based on strain‐energy minimization (L3: trap = propane‐1,2,3‐triamine; 1,2,4‐trab = butane‐1,2,4‐triamine; 1,2,3‐trab = butane‐1,2,3‐triamine; 1,3,4‐trpe = pentane‐1,3,4‐triamine; 1,3,4‐tmeb = 2‐methylbutane‐1,3,4‐triamine; 1,2,4‐trpe = pentane‐1,2,4‐triamine; L2: en = ethane‐1,2‐diamine; pn = propane‐1,2‐diamine; X: NH3, OH2, OH−). Equilibration of Co(III) complexes was achieved by oxygenation of aqueous solutions of Co(II) salts in presence of the ligands. Quantitative isomer distribution was investigated with HPLC, and quantitative analysis of the enantiomeric excess (ee) of the racemic substrate (present in a two‐fold excess) was studied, after chromatographical recovery, by 1H‐NMR analysis of its Mosher‐acid derivative. There is good agreement between calculated and experimental data. Systems with L = 1,2,4‐trab are, as expected, relatively poorly discriminating (ee([Co(1,2,4‐trab)2]3+) ∼ 5%; ee([Co(1,2,4‐trab)(pn)(X)]n+) ∼ 10%). Calculations indicate that Me substitution of the ligand backbone of 1,2,4‐trab (and trap) leads to an increased enantioselectivity (with practically constant isomer selectivity), and at the optimum site for substitution ∼ 90% ee is predicted.

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U2 - 10.1002/hlca.19900730413

DO - 10.1002/hlca.19900730413

M3 - Article

VL - 73

SP - 874

EP - 882

JO - Helvetica Chimica Acta

JF - Helvetica Chimica Acta

SN - 0018-019X

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