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Title
Synthesis and reactivity of the macrobicyclic complexes (1,5,8,12-tetraaza-17-oxabicyclo 10.5.2 nonadecane)cobalt(III) perchlorate ( Co(L-1)(ClO4) (ClO4)(2)), (chloro(1,4,8,11-tetraaza-17-oxabicyclo 9.5.3 nonadecane)cobalt(III) perchlorate ( Co(L-2)(Cl) (ClO4)(2)), (4,8-dimethyl-1,4,8,11-tetraaza-17-oxabicyclo 9.5.3 nonadecane)cobalt(II I) perchlorate ( Co(L-3)(ClO4) (ClO4)(2)), and (5,8-dimethyl-1,5,8,12-tetraaza-17-oxabicyclo 10.5.2 nonadecane)cobalt(I II) perchlorate ( Co(L-4)(ClO4) (ClO4)(2)) - Crystal structure of the L-2 complex
Author/Creator
Rodopoulos, Theo;  Ishihara, Koji;  Rodopoulos, Mary;  Zaworotko, M.;  Maeder, Marcel;  McAuley, A.
Description
The potentially penta-coordinating ligands L-2 and L-3 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 (L-3). A similar procedure is outlined for the dimethylated macrobicycle (L-4), 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 L-1 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 L-2 exhibit remarkable kinetic stability. Studies on the anation of the [Co(L-1)(H2O)](ClO4)(3) with chloride ions in acidic media are consistent with the reaction of both the proton-related complex and the [Co(L-1)(H2O)](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.
Relation
Canadian Journal of Chemistry-Revue Canadienne De Chimie Vol. 83, no. 6, p. 894-902
Date
2005
Publisher
National Research Council
Keyword(s)
cobalt( III);  macrobicycle;  hydrolysis;  anation;  spectroscopic analysis;  substitution-reactions;  template synthesis;  ligand;  copper(ii);  ion;  nickel(ii);  kinetics
Resource Type
journal article
Identifier
http://hdl.handle.net/1959.13/24589
Identifier
ISSN:0008-4042
Language
eng
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"Canadian Journal of Chemistry-Revue Canadienne De Chimie"
 
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