Issue 37, 2008

The donor ability of the chelated carbonateligand: protonation and metallation of [(L)Co(O2CO)]+ complexes in aqueous solution

Abstract

The syntheses and X-ray structures of [Co(Me-tpa)O2COZnCl3], [Co(pmea)O2COZnCl3]·H2O [Co(trpyn)O2COZn(OH2)4OCO2Co(trpyn)](ZnCl4)2·H2O, [Co(trpyn)(O2COH)]ZnCl4·3H2O and [Co(trpyn)(O2CO)]ClO4 are reported (Me-tpa = [(6-methyl-2-pyridyl)methyl]bis(2-pyridylmethyl)amine, pmea = bis(2-pyridylmethyl)-2-(2-pyridylethyl)amine, trpyn = tris(2-(1-pyrazolyl)ethyl)amine). The chelated bicarbonate complex [Co(trpyn)(O2COH)]ZnCl4·3H2O is isolated as a crystalline solid from an acidic solution of the parent carbonate [Co(trpyn)(O2CO)]ClO4, and X-ray structural analysis shows that lengthening of the C[double bond, length as m-dash]Oexo bond and shortening of the C–Oendo bond accompanies protonation. The bimetallic complex [Co(Me-tpa)O2COZnCl3] results from the unexpected coordination of ZnCl3 to the exoO atom of a chelated carbonate ligand. This complex is obtained from both acidic and neutral solutions in which [Zn2+] = 1.0 M, while the structurally similar complex [Co(pmea)O2COZnCl3]·H2O is isolated from an analogous neutral solution. The trimetallic complex [Co(trpyn)O2COZn(OH2)4OCO2Co(trpyn)](ZnCl4)2·H2O crystallises on prolonged standing of [Co(trpyn)(O2CO)]ClO4 in a neutral solution having [Zn2+] = 1.0 M. The Zn–O bond lengths in all three complexes are indicative of bonds of significant strength. DFT calculations show that the nature of the bonding interaction between the Co(III) ion and the endoO atoms of the carbonate ligand remain essentially unaffected by coordination of Zn2+ to the exoO atom. They also show that such coordination of Zn2+ decreases the C–Oexo bond order.

Graphical abstract: The donor ability of the chelated carbonate ligand: protonation and metallation of [(L)Co(O2CO)]+ complexes in aqueous solution

Supplementary files

Article information

Article type
Paper
Submitted
24 Apr 2008
Accepted
06 Jun 2008
First published
31 Jul 2008

Dalton Trans., 2008, 4984-4992

The donor ability of the chelated carbonate ligand: protonation and metallation of [(L)Co(O2CO)]+ complexes in aqueous solution

L. F. McClintock, G. Cavigliasso, R. Stranger and A. G. Blackman, Dalton Trans., 2008, 4984 DOI: 10.1039/B806981F

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