Tris(acetylacetonato)cobalt(III)

Tris(acetylacetonato)cobalt(III) is the coordination complex with the formula Co(C5H7O2)3. Often abbreviated Co(acac)3, it is a green, diamagnetic solid that is soluble in organic solvents, but not in water. Owing to its solubility in organic solvents, tris(acetylacetonato)cobalt(III) is used to produce homogeneous catalysts by reduction.[1]

Tris(acetylacetonato)cobalt(III)
Names
Other names
Cobalt(III) acetylacetonate, tris(acac) cobalt
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.040.464
EC Number
  • 244-527-6
  • InChI=1S/3C5H8O2.Co/c3*1-4(6)3-5(2)7;/h3*3,6H,1-2H3;/q;;;+3/p-3/b3*4-3+;
    Key: RHCQEPWEBDOALW-MUCWUPSWSA-K
  • C/C(=C\C(=O)C)/[O-].C/C(=C\C(=O)C)/[O-].C/C(=C\C(=O)C)/[O-].[Co+3]
Properties
C15H21CoO6
Molar mass 356.260 g·mol−1
Appearance green solid
Density 1.41 g/cm3
Melting point 213 °C (415 °F; 486 K)
Hazards
GHS labelling:
GHS07: Exclamation markGHS08: Health hazard
Danger
H302, H317, H334
P261, P264, P270, P272, P280, P285, P301+P312, P302+P352, P304+P341, P321, P330, P333+P313, P342+P311, P363, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Structure

The structure of the complex has been confirmed by X-ray crystallography. The three acac- ligands bind in a bidentate fashion to cobalt, defining an octahedral complex.[2] The solid is isomorphous with tris(acetylacetonato)iron(III), tris(acetylacetonato)manganese(III), and tris(acetylacetonato)aluminium. With D3-symmetry, these complexes are chiral and often can be resolved into the individual enantiomers.

Synthesis and reactions

Tris(acetylacetonato)cobalt(III) is prepared by the reaction of cobalt(II) carbonate and acetylacetone in the presence of hydrogen peroxide:[3]

2 CoCO3 + 6 CH3COCH2COCH3 + H2O2 → 2 Co(O2C3Me2H)3 + 2 CO2 + 4 H2O

One distinctive aspect of Co(acac)3 is its susceptibility toward electrophilic aromatic substitution, by which protons on the central carbon are replaced with diverse electrophiles (Me = methyl):[4]

Co(O2C3Me2H)3 + 3 NO2+ → Co(O2C3Me2NO2)3 + 3 H+

References
  1. Mayo, Peter D.; Tam, William (2002). "Tris(acetoacetonyl)cobalt". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn00084. ISBN 0471936235.
  2. Arslan, Evrim; Lalancette, Roger A.; Bernal, Ivan (2017). "An Historic and Scientific Study of the Properties of Metal(III) Tris-acetylacetonates". Structural Chemistry. 28: 201–212. doi:10.1007/s11224-016-0864-0. S2CID 99668641.
  3. Bryant, Burl E.; Fernelius, W. Conard (1957). "Cobalt(III) Acetylacetonate". Inorganic Syntheses. 5: 188–189. doi:10.1002/9780470132364.ch53. ISBN 9780470132364.
  4. Shalhoub, George M. (1980). "Co(acac)3 Synthesis, Reactions, and Spectra: An Experiment for General Chemistry". Journal of Chemical Education. 57 (7): 525. Bibcode:1980JChEd..57..525S. doi:10.1021/ed057p525.
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