Chromium(III) acetylacetonate

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Chromium(III) acetylacetonate[1]
Lambda-tris(acetylacetonato)manganese(III)-3D-balls.png
Solid Chromium (III) acetylacetonate
Solid chromium(III) acetylacetonate
Names
IUPAC name
Tris(acetylacetonato)chromium(III)
Other names
Tris(2,4-pentanediono)chromium(III), Cr(acac)3, Cr(pd)3
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.040.463 Edit this at Wikidata
EC Number
  • 244-526-0
  • InChI=1S/3C5H7O2.Cr/c3*1-4(6)3-5(2)7;/h3*3H,1-2H3;/q3*-1;+3 checkY
    Key: GMJCSPGGZSWVKI-UHFFFAOYSA-N checkY
  • InChI=1/3C5H7O2.Cr/c3*1-4(6)3-5(2)7;/h3*3H,1-2H3;/q3*-1;+3
    Key: GMJCSPGGZSWVKI-UHFFFAOYAF
  • [Cr+3].O=C([CH-]C(=O)C)C.O=C([CH-]C(=O)C)C.O=C([CH-]C(=O)C)C
Properties
Cr(C5H7O2)3
Molar mass 349.32
Appearance deep maroon
Density 1.34 g/cm3
Melting point 210 °C (410 °F; 483 K)
Boiling point 340 °C (644 °F; 613 K) (sublimes near 100 °C)
Solubility in non-polar organic solvents soluble
Hazards
GHS labelling:
GHS07: Exclamation mark
Signal word
 Warning
H315, H319, H335
P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY  (what is checkY☒N ?)
Infobox references

Chromium(III) acetylacetonate is the coordination compound with the formula Cr(C5H7O2)3, sometimes designated as Cr(acac)3. This purplish coordination complex is used in NMR spectroscopy as a relaxation agent because of its solubility in nonpolar organic solvents and its paramagnetism.

Synthesis and structure[]

The compound is prepared by the reaction of chromium(III) oxide with acetylacetone (Hacac):[2]

Cr2O3 + 6 Hacac → 2 Cr(acac)3 + 3 H2O

The complex has idealized D3 symmetry. The Cr-O distances are 1.93 Å.[3] The complex has been resolved into individual enantiomers by separation of its adduct with dibenzoyltartrate.[4]

Like many other Cr(III) compounds, it has a quartet ground state.

The complex is relatively inert toward substitution but undergoes bromination at the 3-positions of the chelate rings.

Use in NMR[]

The addition of small quantities of Cr(acac)3 to an NMR sample can allow for quantitative 13C NMR, i.e. accurate relative integrations of peaks. It achieves this by acting as a paramagnetic relaxation reagent which cancels out the Nuclear Overhauser effect, which can adversely effect the integration of 13C peaks.[5]

See also[]

References[]

  1. ^ Chromium acetylacetonate Archived 2015-04-16 at the Wayback Machine at American Elements
  2. ^ Fernelius, W. Conard; Blanch, Julian E. (2007). "Chromium(III) Acetylacetonate". Inorganic Syntheses. Vol. 5. pp. 130–131. doi:10.1002/9780470132364.ch35. ISBN 9780470132364.
  3. ^ Morosin, B. (1965). "The crystal structure of trisacetylacetonatochromium(III)". Acta Crystallographica. 19: 131–137. doi:10.1107/S0365110X65002876.
  4. ^ Drake, A. F.; Gould, J. M.; Mason, S. F.; Rosini, C.; Woodley, F. J. (1983). "The optical resolution of tris(pentane-2,4-dionato)metal(III) complexes". Polyhedron. 2 (6): 537–538. doi:10.1016/S0277-5387(00)87108-9.{{cite journal}}: CS1 maint: uses authors parameter (link)
  5. ^ Cookson, David J; Smith, Brian E (May 1984). "Optimal conditions for obtaining quantitative 13C NMR, data". Journal of Magnetic Resonance. 57 (3): 355–368. Bibcode:1984JMagR..57..355C. doi:10.1016/0022-2364(84)90253-1.
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