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Metallamine complex - Metal ammine complex

In <) 106="">Coordination chemistry, Metal amine complexes are metal complexes that contain at least one ammonia (NH 3) Ligand. "Ammin" is spelled this way for historical reasons, as opposed to spelling alkyl or aryl-bearing ligands with a single "m". Almost all metal ions bind ammonia as ligands, but the most common examples of amine complexes are Cr (III). , Co (III), Ni (II), Cu (II) and several metals of the platinum group.

history

Ammin complexes played a major role in the development of coordination chemistry, particularly the determination of stereochemistry and structure. They are easy to manufacture and the metal-nitrogen ratio can be determined by elemental analysis. Alfred Werner developed his Nobel Prize-winning concept for the structure of coordination compounds through studies mainly on ammine complexes (see figure).

One of the first amine complexes to be described was Magnus' green salt, which consists of the platinum tetrammine complex [Pt (NH 3)4].

Examples

Homoleptic poly (ammin) complexes are known for many of the transition metals. Most often they have the formula [M (NH 3)6], where n = 2, 3 and even 4 (M = Pt).

Platinum group metals

Platinum group metals form various amine complexes. Pentaamin (dinitrogen) ruthenium (II) and the Creutz-Taube complex are well-studied examples or historical significance. The complex cis-PtCl 2 (NH 3)2under the name cisplatin is an important cancer drug. Pentammine rhodium chloride is the dichloride salt of the dicationic pentammine complex [RhCl (NH 3)5)]. This salt is an intermediate in the purification of rhodium from its ores.

Cobalt (III) and chromium is used (III)

The amines of chromium (III) and cobalt (III) are of historical importance. Both families of ammines are kinetically relatively inert, which enables isomers to be separated. For example, tetraammine dichlorochromium (III) chloride [Cr (NH226] Cl) has two forms - the cis isomer is purple while the trans isomer is green. The trichloride of hexaammine (hexammine cobalt (III) chloride, [Co (NH 3)6] Cl114>) exists only as a single isomer. "Reineckes Salz" with the formula NH114 [Cr (NCS) 4 (NH 3)2].H2O was first reported in 1863.

Nickel (II), zinc (II), copper (II)

Sample of chloropentammine cobalt chloride [CoCl (NH 3)5] Cl 2 Metallamine complexes, which exemplifies the vibrant colors typical of the transition.

Zinc (II) forms a colorless tetraammine with the formula [Zn (NH 3)4]]. Like most zinc complexes, it has a tetrahedral structure. Hexaammine nickel is purple and the copper (II) complex is deep blue. The latter is characteristic of the presence of copper (II) in the qualitative inorganic analysis.

Copper (I), silver (I) and gold (I)

Copper (I) forms only labile complexes with ammonia, including the trigonal planar [Cu (NH 3)3]. Silver gives the diammine complex [Ag (NH 3)2] with linear coordination geometry). It is this complex that forms when it contains otherwise insoluble silver chloride and dissolves in aqueous ammonia. The same complex is the active ingredient in Tollen's reagent. Gold (I) chloride forms a compound with six ammonia, but X-ray crystallography shows that only two ammonia molecules are ligands.

Reactions

Ligand exchange and redox reactions

Since ammonia is a stronger ligand in the spectrochemical series, metal amine complexes are stabilized towards water compared to the corresponding aquo complexes. For similar reasons, metalamine complexes oxidize less strongly than the Cor-reacting aquokomplexes. The latter property is illustrated by the stability of [Co (NH242]] in aqueous solution and the absence of [Co (H238]] (which would oxidize water).

Acid-base reactions

After complexing with a metal ion, ammonia is not basic. This property is illustrated by the stability of some metal amine complexes in strongly acidic solutions. When the M-NH316 bond is weak, the amine ligand dissociates and protonation occurs. The behavior is determined by the non-reaction and reaction with [Co (NH 3)6] or [Ni (NH 3)6]] illustrates.

The amine ligands are more acidic than ammonia (pK11a ~ 33). For highly cationic complexes such as 72 [Pt (NH233>) the conjugate base can be obtained. The deprotonation of cobalt (III) amine halide complexes, e.g. B. [CoCl (NH 3)5]) stabilizes the Co-Cl bond according to the Sn1CB mechanism.

Applications

Metallamine complexes find many uses. Cisplatin (PtCl 2 (NH 3)2) is a coordination compound and contains two chlorine and two amine ligands. This is a drug used to treat cancer. Many other platinum group metal amine complexes have been evaluated for this application.

In the separation of the individual platinum metals from their ore, several schemes are based on the precipitation of [RhCl (NH 3)5] Cl 2 . In some separation schemes, palladium is purified by manipulating equilibria that involve [Pd (NH241] Cl11216, PdCl1116 (NH245>), and Pt (NH241 [PdCl114144)>].

When processing cellulose, the Swiss reagent ([Cu (NH 3)4(H2O)2] (OH) known copper amine complex used 2164) is sometimes used to solubilize the polymer. The Schweizer reagent is produced by treating an aqueous solution of copper (II) ions with ammonia. At first, the light blue hydroxide only precipitates only to dissolve again when more ammonia is added: 284 [Cu (H 238] + 2 OH → Cu (OH) 114 2 164 + 6 H 263 Cu (OH) 114 2 164 + 4 NH 114 3 164 + 2 H 2 164 O → [Cu (NH 205]] + 2 OH 270 Diurine fluoride 88 ([Ag (NH 245] F) is a topical drug 83) (drug) for the treatment and prevention of dental caries (cavities) and to alleviate dental hygiene persensitivity.

See also

credentials

  1. ^A. von Zelewsky "Stereochemistry of Coordination Compounds" John Wiley: Chichester, 1995. ISBN 0-471-95599-X.
  2. ^Alfred Werner "Contribution to the constitution of inorganic compounds" Journal for inorganic chemistry 1893, Volume 3, pages 267-330. doi: 10.1002 / zaac.18930030136
  3. ^"Werner Centennial" George B. Kauffman, Ed. Adv. Chem. Ser., 1967, Volume 62. ISBN 978-0-8412-0063-0
  4. ^von Zelewsky, A. "Stereochemistry of Coordination Compounds" John Wiley: Chichester, 1995 ISBN 0-471-95599-X.
  5. ^Atoji, M .; Richardson, J. W .; Rundle, R. E. (1957). "On the crystal structures of the Magnus salts Pt (NH 3)4PtCl 4 ". J. Am. Chem. Soc. 79(12): 3017-3020. doi: 10.1021 / ja01569a009.
  6. ^Eßmann, Ralf, Kreiner, Guido, Niemann, Anke, Rechenbach, Dirk, Schmieding, Axel, Sichla, Thomas, Zachwieja, Uwe, Jacobs, Herbert (1996). "Isotype Prepare the hexaammine metal (II) halide of 3d metals: [V (NH 3)6] I2, [Cr (NH 3)6] I2, [Mn (NH 3)6] Cl 2 , [Fe (NH242] Cl2162, [Fe (NH242] Br1121616, [Co (NH242] Br112164, and [Ni (NH242] Cl114164). "Journal of Inorganic and General Chemistry .97 62278: 1161-1166 .35 doi: 88: 10.1002 /. zaac.19966220709.
  7. ^Basolo, F .; Pearson, RG "Mechanisms of Inorganic Reactions". John Wiley and Son: New York: 1967. ISBN 0-471-05545- X 232 Reinecke, A. "About Rhodanchromammonium Compounds" Annalen der Chemie und Pharmacie, Volume 126, Pages 113-118 (1863). 35 doi: 88: 39 10.1002 / jlac.18631260116 223 Essmann, R. (1995). "Influence of coordination on N-H ... X hydrogen bonds. Part 1. [Zn (NH 3)4] Br 2 and [Zn (NH 3)4] I2". Journal of Molecular Structure. 356 : 201-6. Bibcode: 1995JMoSt.356..201E. doi: 10.1016 / 0022-2860 (95) 08957-W.
  8. ^Nilsson, Kersti B .; Persson, Ingmar (2004). "The coordination chemistry of copper (I) in liquid ammonia, trialkyl and triphenyl phosphite and tri-n-butylphosphine solution". Dalton Transactions (9): 1312-1319. doi: 10.1039 / B400888J.
  9. ^Nilsson, KB; Persson, I .; Kessler, VG (2006) -butylphosphine solutions ". Inorganische Chemie. 45 : 6912. doi: 10.1021 / ic060175v. Quoting has an unknown unknown parameter: (help)
  10. ^Scherf, LM; Baer, ​​SA; Kraus, F .; Bawaked, SM; Schmidbaur, H. (2013). "Implications of the crystal structure of ammonia solvate [Au (NH 3)2] Cl • 4NH 3 ". Inorganic chemistry. 52 : 2157-2161. doi: 10.1021 / ic302550q.
  11. ^S. J. Lippard, J.M. Berg "Principles of Bioinorganic Chemistry" University Science Books: Mill Valley, CA; 1994. ISBN 0-935702-73-3.
  12. ^Rosenblatt, A .; Stamford, T. C. M .; Niederman, R. (2009). "Silver diamine fluoride: a caries" silver fluoride ball "". Journal of Dental Research. 88 : 116-125. doi: 10.1177 / 0022034508329406. PMID 19278981. CS1 maintenance: uses the author parameter (link)