Carbon dioxide activation by cobalt macrocycles: Evidence of hydrogen bonding between bound CO2 and the macrocycle in solution

Etsuko Fujita, Carol Creutz, Norman Satin, Bruce S. Brunschwig

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Abstract

The equilibrium between five-coordinate CoL(CO2)+ (L=5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) and six-coordinate CoL(CO2)(CD3CN)+ (formed at the expense of the five-coordinate form as the temperature is lowered) was examined by both 1H NMR and FT-IR. The equilibration is rapid on the NMR time scale, but the spectra of the limiting forms have been derived from the temperature dependence of the spectrum. The FT-IR spectra measured over the range 25 to -75°C in CD3CN and in a CD3CN/THF mixture indicate the existence of four CO2 adducts, two with intramolecular hydrogen bonds between the bound CO2 and the amine hydrogens of the ligand: a five-coordinate, non-hydrogen-bonded form (νC=O = 1710 cm-1, νNH - 3208 cm-1), a five-coordinate intramolecularly hydrogen-bonded form (νC=O = 1626 cm-1), a six-coordinate non-hydrogen-bonded form (νC=O = 1609 cm-1, νNH = 3224 cm-1), and a six-coordinate intramolecular hydrogen-bonded form (νC=O = 1544 cm-1, νNH = 3145 cm-1). The binding of CO2 via both its electrophilic center (carbon atom) and its nucleophilic center (oxygen atom) is thus implicated in the stabilization of the CO2 complex at low temperature.

Original languageEnglish
Pages (from-to)2657-2662
Number of pages6
JournalInorganic Chemistry
Volume32
Issue number12
Publication statusPublished - 1993

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Cobalt
Carbon Dioxide
carbon dioxide
Hydrogen
Hydrogen bonds
cobalt
Chemical activation
activation
hydrogen
Nuclear magnetic resonance
Atoms
Temperature
Amines
Carbon
Stabilization
Oxygen
Ligands
nuclear magnetic resonance
dienes
adducts

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Carbon dioxide activation by cobalt macrocycles : Evidence of hydrogen bonding between bound CO2 and the macrocycle in solution. / Fujita, Etsuko; Creutz, Carol; Satin, Norman; Brunschwig, Bruce S.

In: Inorganic Chemistry, Vol. 32, No. 12, 1993, p. 2657-2662.

Research output: Contribution to journalArticle

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abstract = "The equilibrium between five-coordinate CoL(CO2)+ (L=5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) and six-coordinate CoL(CO2)(CD3CN)+ (formed at the expense of the five-coordinate form as the temperature is lowered) was examined by both 1H NMR and FT-IR. The equilibration is rapid on the NMR time scale, but the spectra of the limiting forms have been derived from the temperature dependence of the spectrum. The FT-IR spectra measured over the range 25 to -75°C in CD3CN and in a CD3CN/THF mixture indicate the existence of four CO2 adducts, two with intramolecular hydrogen bonds between the bound CO2 and the amine hydrogens of the ligand: a five-coordinate, non-hydrogen-bonded form (νC=O = 1710 cm-1, νNH - 3208 cm-1), a five-coordinate intramolecularly hydrogen-bonded form (νC=O = 1626 cm-1), a six-coordinate non-hydrogen-bonded form (νC=O = 1609 cm-1, νNH = 3224 cm-1), and a six-coordinate intramolecular hydrogen-bonded form (νC=O = 1544 cm-1, νNH = 3145 cm-1). The binding of CO2 via both its electrophilic center (carbon atom) and its nucleophilic center (oxygen atom) is thus implicated in the stabilization of the CO2 complex at low temperature.",
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AU - Brunschwig, Bruce S.

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N2 - The equilibrium between five-coordinate CoL(CO2)+ (L=5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) and six-coordinate CoL(CO2)(CD3CN)+ (formed at the expense of the five-coordinate form as the temperature is lowered) was examined by both 1H NMR and FT-IR. The equilibration is rapid on the NMR time scale, but the spectra of the limiting forms have been derived from the temperature dependence of the spectrum. The FT-IR spectra measured over the range 25 to -75°C in CD3CN and in a CD3CN/THF mixture indicate the existence of four CO2 adducts, two with intramolecular hydrogen bonds between the bound CO2 and the amine hydrogens of the ligand: a five-coordinate, non-hydrogen-bonded form (νC=O = 1710 cm-1, νNH - 3208 cm-1), a five-coordinate intramolecularly hydrogen-bonded form (νC=O = 1626 cm-1), a six-coordinate non-hydrogen-bonded form (νC=O = 1609 cm-1, νNH = 3224 cm-1), and a six-coordinate intramolecular hydrogen-bonded form (νC=O = 1544 cm-1, νNH = 3145 cm-1). The binding of CO2 via both its electrophilic center (carbon atom) and its nucleophilic center (oxygen atom) is thus implicated in the stabilization of the CO2 complex at low temperature.

AB - The equilibrium between five-coordinate CoL(CO2)+ (L=5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) and six-coordinate CoL(CO2)(CD3CN)+ (formed at the expense of the five-coordinate form as the temperature is lowered) was examined by both 1H NMR and FT-IR. The equilibration is rapid on the NMR time scale, but the spectra of the limiting forms have been derived from the temperature dependence of the spectrum. The FT-IR spectra measured over the range 25 to -75°C in CD3CN and in a CD3CN/THF mixture indicate the existence of four CO2 adducts, two with intramolecular hydrogen bonds between the bound CO2 and the amine hydrogens of the ligand: a five-coordinate, non-hydrogen-bonded form (νC=O = 1710 cm-1, νNH - 3208 cm-1), a five-coordinate intramolecularly hydrogen-bonded form (νC=O = 1626 cm-1), a six-coordinate non-hydrogen-bonded form (νC=O = 1609 cm-1, νNH = 3224 cm-1), and a six-coordinate intramolecular hydrogen-bonded form (νC=O = 1544 cm-1, νNH = 3145 cm-1). The binding of CO2 via both its electrophilic center (carbon atom) and its nucleophilic center (oxygen atom) is thus implicated in the stabilization of the CO2 complex at low temperature.

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