Tris(glycinato)cobalt(III)

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Tris(glycinato)cobalt(III)
Fac&merCo(gly)3.svg
Names
Other names
cobalt(III) glycinate
Identifiers
3D model (JSmol)
ChemSpider
PubChem CID
  • InChI=1S/3C2H5NO2.Co/c3*3-1-2(4)5;/h3*1,3H2,(H,4,5);
    Key: WZUSLISJDHJYHZ-UHFFFAOYSA-N
  • C(C(=O)O)N.C(C(=O)O)N.C(C(=O)O)N.[Co]
Properties
Appearanceviolet or reddish solids
0.199 g/L (red isomer, 25 °C), 9.33 g/L (violet, 25 °C) [1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Tris(glycinato)cobalt(III) describes coordination complexes with the formula Co(H2NCH2CO2)3. Several isomers exist of these octahedral complexes formed between low-spin d6 Co(III) and the conjugate base of the amino acid glycine.

Contents

Structures

Solid state structure of mer-Co(glycinate)3 based on X-ray crystallography. SEZMEQ.png
Solid state structure of mer-Co(glycinate)3 based on X-ray crystallography.

Both a meridional isomer and a facial isomer are known. In the former the Co-O bonds share a plane, and in the facial isomer they do not. Each of these two isomers exists also as pairs of stereoisomers, termed Δ and Λ. This set of compounds are prototypes of many tris(aminocarboxylate) complexes, with the notable distinction that the Co(III) derivatives do not isomerize readily and can thus be separated.

The violet isomer is obtained anhydrous, whereas the red derivative is the monohydrate. [1] X-ray crystallographic characterization of the mer isomer demonstrates the existence of a dihydrate, however. [2]

Synthesis

The reaction of glycine with sodium tris(carbonato)cobalt(III) produces both the violet meridional and red-pink facial isomers in approximately equal amounts. The compounds are separated by fractional crystallization. [1] These complexes have been characterized by X-ray crystallography. [3]

The isomeric forms of tris(glycinato)cobalt(III) are poorly soluble in water. The solubility increases considerably in acidic solution.

Other cobalt glycinates

Aside from the isomers of tris(glycinato)cobalt(III), several other cobalt(III) bis(glycinate) complexes are known. Some have the formula [Co(gly)2L2]+ (L2 = bipy and ethylenediamine) [4] and [Co(gly)2(NO2)2]−. [5]

The cobalt(II) derivative Co(gly)2(H2O) has also been characterized. [6]

References

  1. 1 2 3 Kauffman, George B.; Karbassi, Mohammad; Kyuno, Eishin (1989). "Tris(Glycinato)Cobalt(III)". Inorganic Syntheses. Vol. 25. pp. 135–139. doi:10.1002/9780470132562.ch32. ISBN   978-0-470-13256-2.
  2. ↑ Dewan, J. C. (1988). "Structure of Tris(glycinato)cobalt(III) Dihydrate". Acta Crystallographica Section C Crystal Structure Communications. 44 (12): 2199–2201. Bibcode:1988AcCrC..44.2199D. doi:10.1107/S0108270188009126.
  3. ↑ Yu, K.-Q.; Sun, Y.-X.; Zhang, R.; Zhang, N.-W.; Che, H.-W. (2007). "Tris(glycinato-κ2N,O)cobalt(III)". Acta Crystallogr. E63: m740 –m742. doi:10.1107/S1600536807005636.
  4. ↑ Kuramoto, Masahiro (1979). "The Crystal Structures of (+)589- and (−)589-trans-(O)-Ethylenediaminebis(glycinato)cobalt(III) Hydrogen-d-Tartrates and Their Thermal Behavior". Bulletin of the Chemical Society of Japan. 52 (12): 3702–3712. doi:10.1246/bcsj.52.3702.
  5. ↑ Somoza, Fernando; Cai, Jiwen; Bernal, Ivan (1998). "K(H9O4)[cis -Dinitro-Co(trans -N,N-glycinato)2]2 (I)—A Novel Class of Hydronium Ion Traps, of Which (I) Contains an Unusual Form of the H9O4+ Cation". Journal of Coordination Chemistry. 43 (2–3): 187–191. doi:10.1080/00958979808022666.
  6. ↑ Wen, Wu; Jimin, Xie; Yawen, Xuan (2009). "Coordination polymer incorporating cobalt(II) and glycine acid: Structure and magnetism". Journal of Coordination Chemistry. 62 (3): 373–379. doi:10.1080/00958970802283065.
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