Co Dmg 2pyridine Chloride Bf2

10-05-2021
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  1. Co Dmg 2 Pyridine Chloride Bf2 10
  2. Co Dmg 2 Pyridine Chloride Bf2 6
  3. Co Dmg 2 Pyridine Chloride Bf2 3
  4. Co Dmg 2 Pyridine Chloride Bf2 5
  5. Co Dmg 2 Pyridine Chloride Bf2 4

A spectrochemical series is a list of ligands ordered on ligand strength and a list of metal ions based on oxidation number, group and its identity. In crystal field theory, ligands modify the difference in energy between the d orbitals (Δ) called the ligand-field splitting parameter for ligands or the crystal-field splitting parameter, which is mainly reflected in differences in color of similar metal-ligand complexes.

Aug 16, 2015 Cobaloxime model complexes containing aniline derivatives and isothiocyanate as the axial ligands Co(dmgH) 2XY (dmgH = dimethylglyoxime, X = NCS, Cl and Y = aniline, pyridine) have been synthesized and used as proton reduction catalysts.

Spectrochemical series of ligands[edit]

The reactions of nickel(II) chloride with hydrazine, methylhydrazine and 1,1-dimethyl-hydrazine have been investigated. As well as the hydrazine bridged complex Ni(N 2 H 4) 2 Cl 2, nickel(II) chloride forms Ni(N 2 H 4) 3 Cl 2 in which the nickel atom is surrounded by six nitrogen. Chloropentamminecobalt chloride is the dichloride salt of the coordination complex Co(NH 3) 5 Cl 2+. It is a red-violet, diamagnetic, water-soluble salt. The compound has. General description 2,2′:6′,2′′;-Terpyridine is a tridentate ligand that can be prepared in two steps starting from 2-acetylpyridine. Application Due to the presence of three near-coplanar nitrogen donor atoms, 2,2′:6′,2′′;-terpyridine may be used as a metal-binding domain to form metallo-supramolecular structures.

The spectrochemical series was first proposed in 1938 based on the results of absorption spectra of cobalt complexes.[1]

A partial spectrochemical series listing of ligands from small Δ to large Δ is given below. (For a table, see the ligand page.)

I− < Br− < S2− < SCN− (S–bonded) < Cl− < N3− < F−< NCO− < OH− < C2O42− < O2−< H2O < acac− (acetylacetonate) < NCS− (N–bonded) < CH3CN < gly (glycine) < py (pyridine) < NH3 < en (ethylenediamine) < bipy (2,2'-bipyridine) < phen (1,10-phenanthroline) < NO2− < PPh3 < CN− < CO

Weak field ligand: H2O,F-,Cl-,OH-Strong field ligand: CO,CN-,NH3,PPh3

2pyridine

Synthesis of a Cobaltoxime Derivatives1 Cobaloximes have been prepared2,3 and studied extensively as model compounds for the coenzyme vitamin B12.These compounds exist at the interface of classical coordination. Due to the presence of three near-coplanar nitrogen donor atoms, 2,2′:6′,2′′;-terpyridine may be used as a metal-binding domain to form metallo-supramolecular structures. For example, tetraamminedichlorochromium(III) chloride, Cr(NH 3) 4 Cl 2Cl, has two forms - the cis isomer is violet, while the trans isomer is green. The trichloride of the hexaammine ( hexamminecobalt(III) chloride, Co(NH 3 ) 6 Cl 3 )) exists as only a single isomer.

Ligands arranged on the left end of this spectrochemical series are generally regarded as weaker ligands and cannot cause forcible pairing of electrons within the 3d level, and thus form outer orbital octahedral complexes that are high spin. On the other hand, ligands lying at the right end are stronger ligands and form inner orbital octahedral complexes after forcible pairing of electrons within 3d level and hence are called low spin ligands.

However, keep in mind that 'the spectrochemical series is essentially backwards from what it should be for a reasonable prediction based on the assumptions of crystal field theory.'[2] This deviation from crystal field theory highlights the weakness of crystal field theory's assumption of purely ionic bonds between metal and ligand.

The order of the spectrochemical series can be derived from the understanding that ligands are frequently classified by their donor or acceptor abilities. Some, like NH3, are σ bond donors only, with no orbitals of appropriate symmetry for π bonding interactions. Bonding by these ligands to metals is relatively simple, using only the σ bonds to create relatively weak interactions. Another example of a σ bonding ligand would be ethylenediamine, however ethylenediamine has a stronger effect than ammonia, generating a larger ligand field split, Δ.

Ligands that have occupied p orbitals are potentially π donors. These types of ligands tend to donate these electrons to the metal along with the σ bonding electrons, exhibiting stronger metal-ligand interactions and an effective decrease of Δ. Most halide ligands as well as OH− are primary examples of π donor ligands.

When ligands have vacant π* and d orbitals of suitable energy, there is the possibility of pi backbonding, and the ligands may be π acceptors. This addition to the bonding scheme increases Δ. Ligands that do this very effectively include CN−, CO, and many others.[3]

Spectrochemical series of metals[edit]

The metal ions can also be arranged in order of increasing Δ, and this order is largely independent of the identity of the ligand.[4]

Mn2+ < Ni2+ < Co2+ < Fe2+ < V2+ < Fe3+ < Cr3+ < V3+ < Co3+

In general, it is not possible to say whether a given ligand will exert a strong field or a weak field on a given metal ion. However, when we consider the metal ion, the following two useful trends are observed:

  • Δ increases with increasing oxidation number, and
  • Δ increases down a group.[4]

See also[edit]

References[edit]

  • Zumdahl, Steven S. Chemical Principles Fifth Edition. Boston: Houghton Mifflin Company, 2005. Pages 550-551 and 957-964.
  • D. F. Shriver and P. W. Atkins Inorganic Chemistry 3rd edition, Oxford University Press, 2001. Pages: 227-236.
  • James E. Huheey, Ellen A. Keiter, and Richard L. Keiter Inorganic Chemistry: Principles of Structure and Reactivity 4th edition, HarperCollins College Publishers, 1993. Pages 405-408.
  1. ^R. Tsuchida (1938). 'Absorption Spectra of Co-ordination Compounds. I.'Bull. Chem. Soc. Jpn. 13 (5). doi:10.1246/bcsj.13.388.
  2. ^7th page of http://science.marshall.edu/castella/chm448/chap11.pdf
  3. ^Miessler, Gary; Tarr, Donald (2011). Inorganic Chemistry (4th ed.). Prentice Hall. pp. 395–396. ISBN978-0-13-612866-3.
  4. ^ abhttp://www.everyscience.com/Chemistry/Inorganic/Crystal_and_Ligand_Field_Theories/b.1013.php
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Bf2
Ball-and-stick model of the tetraamminediaquacopper(II) cation, [Cu(NH3)4(H2O)2]2+

In coordination chemistry, metal ammine complexes are metal complexes containing at least one ammonia (NH3) ligand. 'Ammine' is spelled this way due to historical reasons; in contrast, alkyl or aryl bearing ligands are spelt with a single 'm'. Almost all metal ions bind ammonia as a ligand, but the most prevalent examples of ammine complexes are for Cr(III), Co(III), Ni(II), Cu(II) as well as several platinum group metals.[1]

History[edit]

Structural representations used by Alfred Werner (right) and Sophus Mads Jørgensen for one isomer of the dichloride salt of the complex [Pt(NH3)2(pyridine)2]2+.[2]

Ammine complexes played a major role in the development of coordination chemistry, specifically determination of the stereochemistry and structure. They are easily prepared, and the metal-nitrogen ratio can be determined by elemental analysis. Through studies mainly on the ammine complexes, Alfred Werner developed his Nobel Prize-winning concept of the structure of coordination compounds (see Figure).[3][4]

One of the first ammine complexes to be described was Magnus' green salt, which consists of the platinum tetrammine complex [Pt(NH3)4]2+.[5]

Examples[edit]

Homoleptic poly(ammine) complexes are known for many of the transition metals. Most often, they have the formula [M(NH3)6]n+ where n = 2, 3, and even 4 (M = Pt).[6]

Platinum group metals[edit]

Platinum group metals form diverse ammine complexes. Pentaamine(dinitrogen)ruthenium(II) and the Creutz–Taube complex are well studied examples or historic significance. The complex cis-PtCl2(NH3)2, under the name Cisplatin, is an important anticancer drug. Pentamminerhodium chloride is the dichloride salt of the dicationic pentammine complex [RhCl(NH3)5]2+. This salt is an intermediate in the purification of rhodium from its ores.

  • Metal-Ammine Complexes

  • Carboplatin, a widely used anticancer drug.

  • Pentamminerhodium chloride, the dichloride salt one a cationic pentammine halide complex.

  • Pentaamine(dinitrogen)ruthenium(II)], the first metal dinitrogen complex.

  • Hexamminecobalt(III) chloride, the trichloride salt of the hexammine complex [Co(NH3)6]3+. It is famously stable in concentrated hydrochloric acid.

  • Reinecke's salt features a very stable anionic diamine complex of Cr(III), which is used as a counteranion.

Cobalt(III) and chromium(III)[edit]

The ammines of chromium(III) and cobalt(III) are of historic significance. Both families of ammines are relatively inert kinetically, which allows the separation of isomers.[7] For example, tetraamminedichlorochromium(III) chloride, [Cr(NH3)4Cl2]Cl, has two forms - the cis isomer is violet, while the trans isomer is green. The trichloride of the hexaammine (hexamminecobalt(III) chloride, [Co(NH3)6]Cl3)) exists as only a single isomer. 'Reinecke's salt' with the formula NH4[Cr(NCS)4(NH3)2].H2O was first reported in 1863.[8]

Nickel(II), zinc(II), copper(II)[edit]

Sample of chloropentamminecobalt chloride [CoCl(NH3)5]Cl2, illustrating the vibrant colors typical of transition metal ammine complexes.

Zinc(II) forms a colorless tetraammine with the formula [Zn(NH3)4]2+.[9] Like most zinc complexes, it has a tetrahedral structure. Hexaamminenickel is violet, and the copper(II) complex is deep blue. The latter is characteristic of the presence of copper(II) in qualitative inorganic analysis.

Copper(I), silver(I), and gold(I)[edit]

Co Dmg 2 Pyridine Chloride Bf2 10

Copper(I) forms only labile complexes with ammonia, including the trigonal planar [Cu(NH3)3]+.[10] Silver gives the diammine complex [Ag(NH3)2]+ with linear coordination geometry.[11] It is this complex that forms when otherwise rather insoluble silver chloride 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 reveals that only two ammonia molecules are ligands.[12]

Reactions[edit]

Ligand exchange and redox reactions[edit]

Since ammonia is a stronger ligand in the spectrochemical series than water, metal ammine complexes are stabilized relative to the corresponding aquo complexes. For similar reasons, metal ammine complexes are less strongly oxidizing than are the corresponding aquo complexes. The latter property is illustrated by the stability of [Co(NH3)6]3+ in aqueous solution and the nonexistence of [Co(H2O)6]3+ (which would oxidize water).

Acid-base reactions[edit]

Once complexed to a metal ion, ammonia is not basic. This property is illustrated by the stability of some metal ammine complexes in strong acid solutions. When the M-NH3 bond is weak, the ammine ligand dissociates and protonation ensues. The behavior is illustrated by the non-reaction and reaction with [Co(NH3)6]3+ and [Ni(NH3)6]2+, respectively.

The ammine ligands are more acidic than is ammonia (pKa ~ 33). For highly cationic complexes such as [Pt(NH3)6]4+, the conjugate base can be obtained. The deprotonation of cobalt(III) ammine-halide complexes, e.g. [CoCl(NH3)5]2+ labilises the Co-Cl bond, according to the Sn1CB mechanism.

Co Dmg 2 Pyridine Chloride Bf2 6

Applications[edit]

Pyridine

Metal ammine complexes find many uses. Cisplatin (PtCl2(NH3)2) is a coordination compound containing two chloro and two ammine ligands. This is a drug used in treating cancer.[13] Many other amine complexes of the platinum group metals have been evaluated for this application.

Co Dmg 2 Pyridine Chloride Bf2 3

In the separation of the individual platinum metals from their ore, several schemes rely on the precipitation of [RhCl(NH3)5]Cl2. In some separation schemes, palladium is purified by manipulating equilibria involving [Pd(NH3)4]Cl2, PdCl2(NH3)2, and Pt(NH3)4[PdCl4].

In the processing of cellulose, the copper ammine complex known as Schweizer's reagent ([Cu(NH3)4(H2O)2](OH)2) is sometimes used to solubilise the polymer. Schweizer's reagent is prepared by treating an aqueous solutions of copper(II) ions with ammonia. Initially, the light blue hydroxide precipitates only to redissolve upon addition of more ammonia:

[Cu(H2O)6]2+ + 2 OH− → Cu(OH)2 + 6 H2O
Cu(OH)2 + 4 NH3 + 2 H2O → [Cu(NH3)4(H2O)2]2+ + 2 OH−

Co Dmg 2 Pyridine Chloride Bf2 5

Silver diammine fluoride ([Ag(NH3)2]F) is a topical medicament (drug) used to treat and prevent dental caries (cavities) and relieve dentinal hypersensitivity.[14]

Co Dmg 2 Pyridine Chloride Bf2 4

See also[edit]

References[edit]

  1. ^A. von Zelewsky 'Stereochemistry of Coordination Compounds' John Wiley: Chichester, 1995. ISBN0-471-95599-X.
  2. ^Alfred Werner 'Beitrag zur Konstitution anorganischer Verbindungen' Zeitschrift für anorganische Chemie 1893, Volume 3, pages 267–330.doi:10.1002/zaac.18930030136
  3. ^'Werner Centennial' George B. Kauffman, Ed. Adv. Chem. Ser., 1967, Volume 62. ISBN978-0-8412-0063-0
  4. ^von Zelewsky, A. 'Stereochemistry of Coordination Compounds' John Wiley: Chichester, 1995. ISBN0-471-95599-X.
  5. ^Atoji, M.; Richardson, J. W.; Rundle, R. E. (1957). 'On the Crystal Structures of the Magnus Salts, Pt(NH3)4PtCl4'. 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 Strukturen einiger Hexaamminmetall(II)‐halogenide von 3d‐Metallen: [V(NH3)6]I2, [Cr(NH3)6]I2, [Mn(NH3)6]Cl2, [Fe(NH3)6]Cl2, [Fe(NH3)6]Br2, [Co(NH3)6]Br2, und [Ni(NH3)6]Cl2'. Zeitschrift für anorganische und allgemeine Chemie. 622: 1161-1166. doi:10.1002/zaac.19966220709.
  7. ^Basolo, F.; Pearson, R. G. 'Mechanisms of Inorganic Reactions.' John Wiley and Son: New York: 1967. ISBN0-471-05545-X
  8. ^Reinecke, A. 'Über Rhodanchromammonium-Verbindungen' Annalen der Chemie und Pharmacie, volume 126, pages 113-118 (1863). doi: 10.1002/jlac.18631260116.
  9. ^Essmann, R. (1995). 'Influence of coordination on N-H...X- hydrogen bonds. Part 1. [Zn(NH3)4]Br2 and [Zn(NH3)4]I2'. Journal of Molecular Structure. 356: 201–6. Bibcode:1995JMoSt.356..201E. doi:10.1016/0022-2860(95)08957-W.
  10. ^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.
  11. ^Nilsson, K. B.; Persson, I.; Kessler, V. G. (2006). 'Coordination Chemistry of the Solvated AgI and AuI Ions in Liquid and Aqueous Ammonia, Trialkyl and Triphenyl Phosphite, and Tri-n-butylphosphine Solutions'. Inorganic Chemistry. 45: 6912. doi:10.1021/ic060175v.
  12. ^Scherf, L. M.; Baer, S. A.; Kraus, F.; Bawaked, S. M.; Schmidbaur, H. (2013). 'Implications of the Crystal Structure of the Ammonia Solvate [Au(NH3)2]Cl·4NH3'. Inorganic Chemistry. 52: 2157-2161. doi:10.1021/ic302550q.
  13. ^S. J. Lippard, J. M. Berg 'Principles of Bioinorganic Chemistry' University Science Books: Mill Valley, CA; 1994. ISBN0-935702-73-3.
  14. ^Rosenblatt, A.; Stamford, T. C. M.; Niederman, R. (2009). 'Silver diamine fluoride: a caries 'silver-fluoride bullet''. Journal of Dental Research. 88: 116–125. doi:10.1177/0022034508329406. PMID19278981.CS1 maint: uses authors parameter (link)
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