Chloropentamminecobalt chloride explained

Chloropentamminecobalt chloride is the dichloride salt of the coordination complex [Co(NH₃)₅Cl]²⁺. It is a red-violet, diamagnetic, water-soluble salt. The compound has been of academic and historical interest.

Synthesis and reactions

The salt is prepared with a two-step process starting with oxidizing a solution of cobalt chloride and ammonia.^{[1] [2]}

2 CoCl₂·6H₂O + 10 NH₃ + 2 HCl + H₂O₂ → 2 [Co(NH₃)₅(OH₂)]Cl₃ + 12 H₂O

This intermediate is then heated to induce coordination of one of the outer sphere chloride ligands:

[Co(NH₃)₅(OH₂)]Cl₃ → [Co(NH₃)₅Cl]Cl₂ + H₂OThe dication [Co(NH₃)₅Cl]²⁺ has idealized C_4v symmetry.^{[3] [4]}

In an aqueous solution, chloropentaamminecobalt(III) chloride reforms aquopentammine complex. With concentrated sulfuric acid, chloropentaamminecobalt(III) chloride forms the hydrogen sulfate complex [Co(NH₃)₅OSO₃H]²⁺.

History

Cobalt complexes have been of long-standing interest in inorganic chemistry because they are numerous, easily prepared, and colorful. It was partly on the basis of his study of cobalt coordination chemistry that Alfred Werner was awarded the Nobel Prize in Chemistry. Prior to Werner, the models of amine complexes postulated chains of pentavalent nitrogen centers. This Jørgensen–Bloomstrand model was overthrown by Werner who introduced the idea that coordination complexes feature metal atoms of octahedral and tetrahedral shapes, with ammonia and other ligands attached individually to the metal. Werner's model accounted for the inner sphere ligands being less reactive.^[5] In [Co(NH₃)₅Cl]Cl₂, two chloride ions are outer sphere (counter ions) and one is bound to the Co(III) center: reaction with excess silver nitrate would immediately precipitate the two chloride counter ions, but the bound chloride ion would not be precipitated.

Health

Also known as CPACC the molecule is investigated in relation with limiting the magnesium available for mitochondria and subsequent metabolic health benefits.^{[6] [7] [8]}

See also

• Pentaamminechlororhodium dichloride

Notes and References

1. Book: Gert G. Schlessinger. Inorganic Syntheses . Chloropentaamminecobalt(III) Chloride . Inorganic Syntheses . 9 . 160 . 1967 . 10.1002/9780470132401.ch43. 9780470132401 .
2. Coordination complexes of cobalt: inorganic synthesis in the general chemistry laboratory . . 1989 . Williams, Gregory M. Olmsted, John, III. Preksa, Andrew P., III . 10.1021/ed066p1043. 66 . 12 . 1043–5. 1989JChEd..66.1043W .
3. G. G. Messmer. E. L. Amma. Redetermination of the crystal structure of chloropentaamminecobalt(III) dichloride . Acta Crystallogr. B . 24 . 417–422 . 1968 . 3. 10.1107/S0567740868002475.
4. Comparisons of π-bonding and hydrogen bonding in isomorphous compounds: [M(NH₃)₅Cl]Cl₂ (M = Cr, Co, Rh, Ir, Ru, Os) . Inorganic Chemistry . 1986 . Hambley, Trevor W.. Lay, Peter A. . 10.1021/ic00245a020. 25 . 25 . 4553–8.
5. Schwab. E.. Cobalt. Chemical & Engineering News. 8 September 2003. 81. 36. 80. 10.1021/cen-v081n036.p080.
6. Web site: Antonio . University of Texas Health Science Center at San . 2023-04-09 . Magnesium Magic: New Drug Delivers Weight Loss Even on Sugary, Fatty Diet . 2023-04-10 . SciTechDaily . en-us.
7. Madaris . Travis R. . Venkatesan . Manigandan . Maity . Soumya . Stein . Miriam C. . Vishnu . Neelanjan . Venkateswaran . Mridula K. . Davis . James G. . Ramachandran . Karthik . Uthayabalan . Sukanthathulse . Allen . Cristel . Osidele . Ayodeji . Stanley . Kristen . Bigham . Nicholas P. . Bakewell . Terry M. . Narkunan . Melanie . 2023-03-28 . Limiting Mrs2-dependent mitochondrial Mg2+ uptake induces metabolic programming in prolonged dietary stress . Cell Reports . 42 . 3 . 112155 . 10.1016/j.celrep.2023.112155 . 2211-1247 . 36857182. 10134742 .
8. Web site: Sansom . Will . 2023-03-21 . Novel drug makes mice slim even on sugary, fatty diet . 2023-04-10 . UT Health San Antonio . en-US.