Tris(acetylacetonato)cobalt(III)

Tris(acetylacetonato)cobalt(III)
Names
	Other names Cobalt(III) acetylacetonate, tris(acac) cobalt
Identifiers
CAS Number	21679-46-9;
3D model (JSmol)	Interactive image;
ChemSpider	4589065;
ECHA InfoCard	100.040.464
EC Number	244-527-6;
PubChem CID	24884269;
CompTox Dashboard (EPA)	DTXSID30893462 ;
	InChI InChI=1S/3C5H8O2.Co/c31-4(6)3-5(2)7;/h33,6H,1-2H3;/q;;;+3/p-3/b3*4-3+; Key: RHCQEPWEBDOALW-MUCWUPSWSA-K;
	SMILES C/C(=C\C(=O)C)/[O-].C/C(=C\C(=O)C)/[O-].C/C(=C\C(=O)C)/[O-].[Co+3];
Properties
Chemical formula	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:
Pictograms
Signal word	Danger
Hazard statements	H302, H317, H334
Precautionary statements	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

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]

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

^ Mayo, Peter D.; Tam, William (2002). "Tris(acetoacetonyl)cobalt". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn00084. ISBN 0-471-93623-5.
^ 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.
^ Bryant, Burl E.; Fernelius, W. Conard (1957). Cobalt(III) Acetylacetonate. Inorganic Syntheses. Vol. 5. pp. 188–189. doi:10.1002/9780470132364.ch53. ISBN 978-0-470-13236-4.
^ 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.

[1] Mayo, Peter D.; Tam, William (2002). "Tris(acetoacetonyl)cobalt". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn00084. ISBN 0-471-93623-5.

[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. Vol. 5. pp. 188–189. doi:10.1002/9780470132364.ch53. ISBN 978-0-470-13236-4.

[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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