Synthesis and reactivity of the macrobicyclic complexes (1,5,8,12-tetraaza-17-oxabicyclo[10.5.2]-nonadecane)cobalt(III) perchlorate ([Co(L1)(CIO4)]-(CIO4)2), [(chloro(1,4,8,11-tetraaza-17-oxabicyclo-[9.5.3]nonadecane)cobalt(III) perchlorate ([Co(L2)-(CI)](CIO4)2)

Theo Rodopoulos, Koji Ishihara, Mary Rodopoulos, M. J. Zaworotko, M. Maeder, A. McAuley

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

The potentially penta-coordinating ligands L2 and L3 have been synthesized by reaction of the 10-membered macrocycle 1,5-diaza-8-oxacyclodecane with either 1,9-dichloro-3,7-diazanonane-2,8-dione, and subsequent reduction of the diamide (3), or with 1,9-dichloro-3,7-(dimethyl) diazanonane-2,8-dione and reduction (L3)-. A similar procedure is outlined for the dimethylated macrobicycle (L4), based on the corresponding nine-membered 1,4-diaza-7-oxacyclononane. The Co(III) complexes of these ligands and of 1,5,8,12-tetraaza-17-oxabicyclo[10.5.2]nonadecane (L 1) have been prepared. Spectrophotometric determinations on the L1 complex ion confirm the presence of two hydrogen ion related equilibria, one of which (pK = 2.2 ± 0.2) is associated with the proposed replacement of the apical ether oxygen by a water molecule that is bound to the metal centre and hydrogen bonded to the ether. The species derived from L 1 and L2 exhibit remarkable kinetic stability. Studies on the anation of the [Co(L1)(H2O)](CIO4) 3 with chloride ions in acidic media are consistent with the reaction of both the proton-related complex and the [Co(L1)(H 2O)]3+ ion. Whilst complex ions containing two secondary NH groups maintain the metal-ion coordination in strongly acidic media, corresponding species with ligands containing all four tertiary amine sites are subject to attack by protons leading to a relatively facile demetallation of the complexes. The latter finding is supported by kinetic studies and mass spectrometric fragmentation patterns of the ions.

Original languageEnglish
Pages (from-to)894-902
Number of pages9
JournalCanadian Journal of Chemistry
Volume83
Issue number6-7
DOIs
Publication statusPublished - 2005 Jun 1

Keywords

  • Anation
  • Cobalt(III)
  • Hydrolysis
  • Macrobicycle
  • Spectroscopic analysis

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Organic Chemistry

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