Hexaamminecobalt(III) chloride is the chemical compound with the formula [Co(NH3)6]Cl3. It is the chloride salt of the coordination complex [Co(NH3)6]3+, which is considered an archetypal "Werner complex", named after the pioneer of coordination chemistry, Alfred Werner. The cation itself is a metal ammine complex with six ammonialigands attached to the cobalt(III) ion.
Originally salts of [Co(NH3)6]3+ were described as the luteo (Latin: yellow) complex of cobalt. This name has been discarded as modern chemistry considers color less important than molecular structure. Other similar complexes also had color names, such as purpureo (Latin: purple) for a cobalt pentammine complex, and praseo (Greek: green) and violeo (Latin: violet) for two isomeric tetrammine complexes.[1]
[Co(NH3)6]3+ is diamagnetic, with a low-spin 3d6octahedral Co(III) center. The cation obeys the 18-electron rule and is considered to be a classic example of an exchange inert metal complex. As a manifestation of its inertness, [Co(NH3)6]Cl3 can be recrystallized unchanged from concentrated hydrochloric acid: the NH3 is so tightly bound to the Co(III) centers that it does not dissociate to allow its protonation.[2] In contrast, labile metal ammine complexes, such as [Ni(NH3)6]Cl2, react rapidly with acids, reflecting the lability of the Ni(II)–NH3 bonds. Upon heating, hexamminecobalt(III) begins to lose some of its ammine ligands, eventually producing a stronger oxidant.
The chloride ions in [Co(NH3)6]Cl3 can be exchanged with a variety of other anions such as nitrate, bromide, iodide, sulfamate to afford the corresponding [Co(NH3)6]X3 derivative. Such salts are orange or bright yellow and display varying degrees of water solubility. The chloride ion can be also exchanged with more complex anions such as the hexathiocyanatochromate(III), yielding a pink compound with formula [Co(NH3)6][Cr(SCN)6], or the ferricyanide ion.
The acetate salt can be prepared by aerobic oxidation of cobalt(II) acetate, ammonium acetate, and ammonia in methanol.[4] The acetate salt is highly water-soluble to the level of 1.9 M (20 °C), versus 0.26 M for the trichloride.
UsesEdit
[Co(NH3)6]3+ is a component of some structural biology methods (especially for DNA or RNA, where positive ions stabilize tertiary structure of the phosphate backbone), to help solve their structures by X-ray crystallography[5] or by nuclear magnetic resonance.[6] In the biological system, the counterions would more probably be Mg2+, but the heavy atoms of cobalt (or sometimes iridium, as in PDB: 2GIS) provide anomalous scattering to solve the phase problem and produce an electron-density map of the structure.[7]
[Co(NH3)6]3+ is an unusual example of a water-soluble trivalent metal complex and is of utility for charge-shielding applications such as the stabilization of highly negatively charged complexes, such as interactions with and between nucleic acids. The compound induced the transition of DNA structure from the classical B-form to the Z-form.[8]
^Huheey, James E. (1983). Inorganic Chemistry (3rd ed.). p. 360.
^ abBjerrum, J.; McReynolds, J. P. (1946). "Hexamminecobalt(III) Salts". Inorg. Synth.2: 216–221. doi:10.1002/9780470132333.ch69.
^Fremy, M. E. (1852). "Recherches sur le cobalt". Ann. Chim. Phys.35: 257–312.
^Lindholm, R. D.; Bause, Daniel E. (1978). "Complexes of Cobalt Containing Ammonia or Ethylene Diamine: Hexaamminecobalt(III) Salts". Inorg. Synth.18: 67–69. doi:10.1002/9780470132494.ch14.
^Ramakrishnan, B.; Sekharudu, C.; Pan, B.; Sundaralingam, M. (2003). "Near-atomic resolution crystal structure of an A-DNA decamer d(CCCGATCGGG): cobalt hexammine interaction with A-DNA". Acta Crystallogr. D59 (Pt 1): 67–72. doi:10.1107/s0907444902018917. PMID 12499541.
^Rudisser, S.; Tinoco, I., Jr. (2000). "Solution structure of Cobalt(III)hexammine complexed to the GAAA tetraloop, and metal-ion binding to G.A mismatches". J. Mol. Biol. 295 (5): 1211–1232. doi:10.1006/jmbi.1999.3421. PMID 10653698.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^McPherson, Alexander (2002). Introduction to Macromolecular Crystallography. John Wiley & Sons. ISBN0-471-25122-4.
hexamminecobalt, chloride, hexaamminecobalt, chloride, chemical, compound, with, formula, chloride, salt, coordination, complex, which, considered, archetypal, werner, complex, named, after, pioneer, coordination, chemistry, alfred, werner, cation, itself, met. Hexaamminecobalt III chloride is the chemical compound with the formula Co NH3 6 Cl3 It is the chloride salt of the coordination complex Co NH3 6 3 which is considered an archetypal Werner complex named after the pioneer of coordination chemistry Alfred Werner The cation itself is a metal ammine complex with six ammonia ligands attached to the cobalt III ion Hexaamminecobalt III chloride NamesIUPAC name Hexaamminecobalt III chlorideOther names Cobalt hexammine chloride hexaamminecobalt III chlorideIdentifiersCAS Number 10534 89 1 Y3D model JSmol Interactive imageChemSpider 140101ECHA InfoCard 100 030 991EC Number 234 103 9PubChem CID 159295UNII 240056WZHT YCompTox Dashboard EPA DTXSID1044358InChI InChI 1S 3ClH Co 6H3N h3 1H 6 1H3 q 3 p 3Key JXBGZYGSWFSYFI UHFFFAOYSA KSMILES Cl NH3 Co 3 NH3 NH3 NH3 NH3 NH3 Cl Cl PropertiesChemical formula H18N6Cl3CoMolar mass 267 48 g molAppearance yellow or orange crystalsDensity 1 71 g cm3 Melting point decomposesSolubility in water 0 26 M 20 C tribromide 0 04 M 18 C Solubility soluble in NH3StructureCoordination geometry octahedralDipole moment 0 DHazardsOccupational safety and health OHS OSH Main hazards poisonGHS labelling PictogramsSignal word WarningHazard statements H315 H319 H335Precautionary statements P261 P264 P271 P280 P302 P352 P304 P340 P305 P351 P338 P312 P321 P332 P313 P337 P313 P362 P403 P233 P405 P501Related compoundsOther anions Co NH3 6 Br3 Co NH3 6 OAc 3Other cations Cr NH3 6 Cl3 Ni NH3 6 Cl2Related compounds Co H2NCH2CH2NH2 3 Cl3 Co NH3 5 H2O Cl3 Co NH3 5Cl Cl2Except where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa N verify what is Y N Infobox references Originally salts of Co NH3 6 3 were described as the luteo Latin yellow complex of cobalt This name has been discarded as modern chemistry considers color less important than molecular structure Other similar complexes also had color names such as purpureo Latin purple for a cobalt pentammine complex and praseo Greek green and violeo Latin violet for two isomeric tetrammine complexes 1 Contents 1 Properties and structure 2 Preparation 3 Uses 4 Related compounds 5 ReferencesProperties and structure Edit Co NH3 6 3 is diamagnetic with a low spin 3d6 octahedral Co III center The cation obeys the 18 electron rule and is considered to be a classic example of an exchange inert metal complex As a manifestation of its inertness Co NH3 6 Cl3 can be recrystallized unchanged from concentrated hydrochloric acid the NH3 is so tightly bound to the Co III centers that it does not dissociate to allow its protonation 2 In contrast labile metal ammine complexes such as Ni NH3 6 Cl2 react rapidly with acids reflecting the lability of the Ni II NH3 bonds Upon heating hexamminecobalt III begins to lose some of its ammine ligands eventually producing a stronger oxidant The chloride ions in Co NH3 6 Cl3 can be exchanged with a variety of other anions such as nitrate bromide iodide sulfamate to afford the corresponding Co NH3 6 X3 derivative Such salts are orange or bright yellow and display varying degrees of water solubility The chloride ion can be also exchanged with more complex anions such as the hexathiocyanatochromate III yielding a pink compound with formula Co NH3 6 Cr SCN 6 or the ferricyanide ion Preparation Edit Co NH3 6 Cl3 is prepared by treating cobalt II chloride with ammonia and ammonium chloride followed by oxidation Oxidants include hydrogen peroxide or oxygen in the presence of charcoal catalyst 2 This salt appears to have been first reported by Fremy 3 The acetate salt can be prepared by aerobic oxidation of cobalt II acetate ammonium acetate and ammonia in methanol 4 The acetate salt is highly water soluble to the level of 1 9 M 20 C versus 0 26 M for the trichloride Uses Edit Co NH3 6 3 is a component of some structural biology methods especially for DNA or RNA where positive ions stabilize tertiary structure of the phosphate backbone to help solve their structures by X ray crystallography 5 or by nuclear magnetic resonance 6 In the biological system the counterions would more probably be Mg2 but the heavy atoms of cobalt or sometimes iridium as in PDB 2GIS provide anomalous scattering to solve the phase problem and produce an electron density map of the structure 7 Co NH3 6 3 is an unusual example of a water soluble trivalent metal complex and is of utility for charge shielding applications such as the stabilization of highly negatively charged complexes such as interactions with and between nucleic acids The compound induced the transition of DNA structure from the classical B form to the Z form 8 Related compounds EditTris ethylenediamine cobalt III chlorideReferences Edit Huheey James E 1983 Inorganic Chemistry 3rd ed p 360 a b Bjerrum J McReynolds J P 1946 Hexamminecobalt III Salts Inorg Synth 2 216 221 doi 10 1002 9780470132333 ch69 Fremy M E 1852 Recherches sur le cobalt Ann Chim Phys 35 257 312 Lindholm R D Bause Daniel E 1978 Complexes of Cobalt Containing Ammonia or Ethylene Diamine Hexaamminecobalt III Salts Inorg Synth 18 67 69 doi 10 1002 9780470132494 ch14 Ramakrishnan B Sekharudu C Pan B Sundaralingam M 2003 Near atomic resolution crystal structure of an A DNA decamer d CCCGATCGGG cobalt hexammine interaction with A DNA Acta Crystallogr D59 Pt 1 67 72 doi 10 1107 s0907444902018917 PMID 12499541 Rudisser S Tinoco I Jr 2000 Solution structure of Cobalt III hexammine complexed to the GAAA tetraloop and metal ion binding to G A mismatches J Mol Biol 295 5 1211 1232 doi 10 1006 jmbi 1999 3421 PMID 10653698 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint multiple names authors list link McPherson Alexander 2002 Introduction to Macromolecular Crystallography John Wiley amp Sons ISBN 0 471 25122 4 10 1080 07391102 1986 10508453 Retrieved from https en wikipedia org w index php title Hexamminecobalt III chloride amp oldid 1158177761, wikipedia, wiki, book, books, library,
