Cyanometalate

Last updated

Cyanometallates or cyanometalates are a class of coordination compounds, most often consisting only of cyanide ligands. [1] Most are anions. Cyanide is a highly basic and small ligand, hence it readily saturates the coordination sphere of metal ions. The resulting cyanometallate anions are often used as building blocks for more complex structures called coordination polymers, the best known example of which is Prussian blue, a common dyestuff. [2]

Contents

Examples

Homoleptic cyanometallates

Homoleptic cyanometallates are complexes where the only ligand is cyanide. For transition metals, well known homoleptic cyanometallates are the hexacyanides. Hexacyanometalates are known for Ti(III), V(III), Cr(III), Cr(II), Mn(IV), Mn(III), Mn(II), Fe(II), Fe(III), Co(III), Ru(III), Ru(II), Os(III), and Os(II). Other more labile derivatives are also known. The Cr(II), [3] Mn(III), Mn(II), Fe(II), Fe(III), and Co(III) derivatives are low-spin, reflecting the strong binding of cyanide, i.e. cyanide ranks highly in the spectrochemical series when significant backbonding can occur. Since cyanide has the largest σ-donation ability at its C-end, most soluble (molecular) metal-cyanide complexes have metal-carbon, rather than metal-nitrogen bonds. [4] With low d-electron counts, however, inversion of cyanometallates to nitrile complexes can occur. Lower metal oxidation states can be achieved with binding of Lewis acids to the terminal nitrogen lone pairs.

HexacyanidoferratIII 2.svg Ferricyanide-3D.png

Pentacyanocobaltate ([Co(CN)5]3−) is produced by the addition of five or more equivalents of a cyanide to a solution of a cobalt(II) salt. It is square pyramidal. [5] Solutions of [Co(CN)5]−3 undergo a variety of reactions, such as hydrogenation: [6]

2[Co(CN)5]3− + H2 → 2 [Co(CN)5H]3−

Several tetracyanometalates are also known, the best known being those of the d8 metals, Ni(II), Pd(II), and Pt(II). These species are square-planar and diamagnetic. In addition to [Ni(CN)4]4−, nickel also forms [Ni2(CN)6]4-, with a Ni(I)-Ni(I) bond. The coinage metals form stable dicyanometallates, [Cu(CN)2]−, [Ag(CN)2]−, and [Au(CN)2]−. For heavier metals, other stoichiometries are known such as K4Mo(CN)8 and Potassium heptacyanorhenate. Some cyanometallates are clusters featuring metal-metal bonds, such as [Mo2(CN)8]4−.

nameformulaformula weightchargeoxidation

state

commentreference
Tetracyanidoborate[B(CN)4]−−1+3 [7]
HexacyanidosilicateSi(CN)62–−2+4 [8]
Tetracyanotitanate(II)[Ti(CN)4]2−−2+2 [9]
Hexacyanotitanate(III)[Ti(CN)6]3−−3+3orange [9]
Heptacyanotitanate(III)[Ti(CN)7]4−−4+3 [9]
Octacyanotitanate(III)[Ti(CN)8]5−−5+3dark green [9] [10]
Hexacyanovanadate(II)[V(CN)6]4−−4+2yellow brown [10]
Heptacyanovanadate(III)[V(CN)7]4−−4+3scarlet purple [10]
Hexacyanidochromate(0)[Cr(CN)6]6−−60dark green [10]
Hexacyanochromate(III)[Cr(CN)6]3−−3+3pale yellow [10]
Hexacyanomanganate(III)[MnIII(CN)6]3–−3+3
Hexacyanoferrate(II)[FeII(CN)6]4−−4+2 [11]
Tricyanidoferrate(IV)[Fe(CN)3]7−−7−4 [12]
Tricyanocobaltate(III)[Co(CN)3]6−−6−3 [12]
Hexacyanocobaltate(III)[Co(CN)6]3−−3+3
Tetracyanonickelate(II)[Ni(CN)4]2–−2+2yellow orange
Tetracyanonickelate(III)[Ni(CN)4]–−1+3
Hexacyanodinickelate(II)[Ni2(CN)6]4−−4+1
Hexacyanogermanate(IV)Ge(CN)62–−2+4 [8]
Heptacyanomolybdate(III)[Mo(CN)7]4−−4+3dark green [10]
Octacyanomolybdate(IV)[Mo(CN)8]4−−4+4yellow [13] [10]
Tricyanidoruthenate(−IV)[Ru(CN)3]7−−7−4 [12]
Tetracyanopalladate(II)[Pd(CN)4]2–−2+2 [14]
Dicyanidoargentate(I) [Ag(CN)2]–−1+1
Hexacyanostannate(II)Sn(CN)62–−2+4 [8]
Pentacyanoantimonate[Sb(CN)5]2–−2+3 [15]
Heptacyanotungstate(IV)[W(CN)7]3−−3+4 [16]
Octacyanotungstate[W(CN)8]3−−3+5 [17]
Heptacyanorhenate(IV)[Re(CN)7]3–−3+4 [17]
Tetracyanoplatinate(II)[Pt(CN)4]2−−2+2 [18]
Hexacyanoplatinate(IV)[Pt(CN)6]2–−2+4 [17]
Dicyanidoaurate(I) [Au(CN)2]–−1+1
Tetracyanidoaurate(III)[Au(CN)4]–−1+3 [19]
Pentacyanidobismuthate(III)[Bi(CN)5]2–−2+3 [15]
Hexacyanidobismuthate(III)[Bi(CN)6]3–−3+3 [15]
Hendecacyanodibismuthate[Bi2(CN)11]5–−5+3 [15]

Heteroleptic cyanometallates

Mixed ligand cyanometallates with anywhere from one to five cyanide ligands have been prepared. One example is the zero-valent [Fe(CO)4(CN)]−. Heteroleptic cyanometallates are of interest outside of the research laboratory, with one example being the drug sodium nitroprusside (Na2FeNO(CN)5). Other studies have demonstrated their competency as photoredox catalysts.

Synthesis

Because cyanide is a powerful nucleophile and a strong ligand, cyanometallates are generally prepared by the direct reaction of cyanide salts with simple metal salts. If other ligands are present on the metal, these are often displaced by cyanide. By far the largest application of cyanometalates is the production of [Au(CN)2]− in the extraction of gold from low grade ores. This conversion involves oxidation of metallic gold into Au+:

4 Au + 8 CN− + O2 + 2 H2O → 4 [Au(CN)2]− + 4 OH−

Reactions

Redox

Because the M-CN bond is strong and delocalizes electron density to the ligands, several cyanometallates exhibit multiple redox states. A well known couple is [Fe(CN)6]3−/4−. Mn(IV), Mn(III), and Mn(II) are known for hexacyanomanganate. Few unidentate ligands allow similar redox transformations wherein both members of the redox couple are observable in solution. Another perhaps more dramatic example is the 2 e– reduction of the square planar tetracyanonickelate to its tetrahedral Ni(0) derivative:

[Ni(CN)4]2− + 2 e– → [Ni(CN)4]4−

N-Centered reactions

Many characteristic reactions of metal cyanides arise from ambidentate nature of cyanide, i.e. both the nitrogen and the carbon extremities of the anion are basic. Thus cyanometalates can be alkylated to give isocyanide complexes. [20] Cyanide ligands are susceptible to protonation, hence many cyanometalates are highly solvatochromic. The nitrogen terminus is a good ligand for other metals. The latter tendency is illustrated by the condensation of ferrocyanide salts with other metal ions to give polymers, such as Prussian blue. Such polymers feature Fe-CN-M linkages.

See also

Related Research Articles

<span class="mw-page-title-main">Cyanide</span> Any molecule with a cyano group (–C≡N)

In chemistry, cyanide is a chemical compound that contains a C≡N functional group. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom.

<span class="mw-page-title-main">Coordination complex</span> Molecule or ion containing ligands datively bonded to a central metallic atom

A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the coordination centre, and a surrounding array of bound molecules or ions, that are in turn known as ligands or complexing agents. Many metal-containing compounds, especially those that include transition metals, are coordination complexes.

<span class="mw-page-title-main">Cyanate</span> Anion with formula OCN and charge –1

The cyanate ion is an anion with the chemical formula OCN−. It is a resonance of three forms: [O−−C≡N] (61%) ↔ [O=C=N−] (30%) ↔ [O+≡C−N2−] (4%).

<span class="mw-page-title-main">Metal ammine complex</span> Class of chemical compounds

In coordination chemistry, metal ammine complexes are metal complexes containing at least one ammonia ligand. "Ammine" is spelled this way for 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.

<span class="mw-page-title-main">Metal carbonyl</span> Coordination complexes of transition metals with carbon monoxide ligands

Metal carbonyls are coordination complexes of transition metals with carbon monoxide ligands. Metal carbonyls are useful in organic synthesis and as catalysts or catalyst precursors in homogeneous catalysis, such as hydroformylation and Reppe chemistry. In the Mond process, nickel tetracarbonyl is used to produce pure nickel. In organometallic chemistry, metal carbonyls serve as precursors for the preparation of other organometallic complexes.

Iron shows the characteristic chemical properties of the transition metals, namely the ability to form variable oxidation states differing by steps of one and a very large coordination and organometallic chemistry: indeed, it was the discovery of an iron compound, ferrocene, that revolutionalized the latter field in the 1950s. Iron is sometimes considered as a prototype for the entire block of transition metals, due to its abundance and the immense role it has played in the technological progress of humanity. Its 26 electrons are arranged in the configuration [Ar]3d64s2, of which the 3d and 4s electrons are relatively close in energy, and thus it can lose a variable number of electrons and there is no clear point where further ionization becomes unprofitable.

<span class="mw-page-title-main">Metal nitrosyl complex</span> Complex of a transition metal bonded to nitric oxide: Me–NO

Metal nitrosyl complexes are complexes that contain nitric oxide, NO, bonded to a transition metal. Many kinds of nitrosyl complexes are known, which vary both in structure and coligand.

In organometallic chemistry, a transition metal indenyl complex is a coordination compound that contains one or more indenyl ligands. The indenyl ligand is formally the anion derived from deprotonation of indene. The η5-indenyl ligand is related to the η5cyclopentadienyl anion (Cp), thus indenyl analogues of many cyclopentadienyl complexes are known. Indenyl ligands lack the 5-fold symmetry of Cp, so they exhibit more complicated geometries. Furthermore, some indenyl complexes also exist with only η3-bonding mode. The η5- and η3-bonding modes sometimes interconvert.

Metal nitrido complexes are coordination compounds and metal clusters that contain an atom of nitrogen bound only to transition metals. These compounds are molecular, i.e. discrete in contrast to the polymeric, dense nitride materials that are useful in materials science. The distinction between the molecular and solid-state polymers is not always very clear as illustrated by the materials Li6MoN4 and more condensed derivatives such as Na3MoN3. Transition metal nitrido complexes have attracted interest in part because it is assumed that nitrogen fixation proceeds via nitrido intermediates. Nitrido complexes have long been known, the first example being salts of [OsO3N]−, described in the 19th century.

<span class="mw-page-title-main">Cyanonickelate</span> Class of chemical compounds

The cyanonickelates are a class of chemical compound containing anions consisting of nickel atoms, and cyanide groups. The most important of these are the tetracyanonickelates containing four cyanide groups per nickel. The tetracyanonickelates contain the [Ni(CN)4]2− anion. This can exist in solution or in solid salts. The ion has cyanide groups arranged in a square around the central nickel ion. The symmetry of the ion is D4h. The distance from the nickel atom to the carbon is 1.87 Å, and the carbon-nitrogen distance is 1.16 Å. In their crystals, the tetracyanonickelate(II) anions are often arranged in a columnar structure (e.g. in K2[Ni(CN)4]). Tetracyanonickelate(II) can be oxidised electrochemically in solution to yield tetracyanonickelate(III) [Ni(CN)4]−. [Ni(CN)4]− is unstable and Ni(III) oxidises the cyanide to cyanate OCN−. Tetracyanonickelate(III) can add two more cyanide groups to form hexacyanonickelate(III).

<span class="mw-page-title-main">Transition metal nitrile complexes</span> Class of coordination compounds containing nitrile ligands (coordinating via N)

Transition metal nitrile complexes are coordination compounds containing nitrile ligands. Because nitriles are weakly basic, the nitrile ligands in these complexes are often labile.

<span class="mw-page-title-main">Transition metal pyridine complexes</span>

Transition metal pyridine complexes encompass many coordination complexes that contain pyridine as a ligand. Most examples are mixed-ligand complexes. Many variants of pyridine are also known to coordinate to metal ions, such as the methylpyridines, quinolines, and more complex rings.

<span class="mw-page-title-main">Transition metal isocyanide complexes</span> Class of chemical compounds

Transition metal isocyanide complexes are coordination compounds containing isocyanide ligands. Because isocyanides are relatively basic, but also good pi-acceptors, a wide range of complexes are known. Some isocyanide complexes are used in medical imaging.

<span class="mw-page-title-main">Transition metal nitrite complex</span> Chemical complexes containing one or more –NO₂ ligands

In organometallic chemistry, transition metal complexes of nitrite describes families of coordination complexes containing one or more nitrite ligands. Although the synthetic derivatives are only of scholarly interest, metal-nitrite complexes occur in several enzymes that participate in the nitrogen cycle.

<span class="mw-page-title-main">Potassium tetracyanonickelate</span> Chemical compound

Potassium tetracyanonickelate (IUPAC: Potassium tetracyanido nickelate(II)) is the inorganic compound with the formula K2Ni(CN)4. It is usually encountered as the monohydrate but the anhydrous salt is also known. Both are yellow, water-soluble, diamagnetic solids. The salt consists of potassium ions and the tetracyanonickelate coordination complex, which is square planar. The [Ni(CN)4]2- anions are arranged in a columnar structure with Ni---Ni distances of 4.294 Å, which is well beyond the sum of the van der Waals radius of the nickel cation. This columnar structure resembles those of the other [M(CN)4]2- anions of the heavy congeners of the group 10 metals (M = Pd, Pt).

<span class="mw-page-title-main">Transition metal nitrate complex</span> Compound of nitrate ligands

A transition metal nitrate complex is a coordination compound containing one or more nitrate ligands. Such complexes are common starting reagents for the preparation of other compounds.

<span class="mw-page-title-main">Transition metal azide complex</span>

Transition metal azide complexes are coordination complexes containing one or more azide (N3−) ligands. In addition to coordination complexes, this article summarizes homoleptic transition metal azides, which are often coordination polymers.

Sulfidogermanates or thiogermanates are chemical compounds containing anions with sulfur atoms bound to germanium. They are in the class of chalcogenidotetrelates. Related compounds include thiosilicates, thiostannates, selenidogermanates, telluridogermanates and selenidostannates.

<span class="mw-page-title-main">Transition metal ether complex</span>

In chemistry, a transition metal ether complex is a coordination complex consisting of a transition metal bonded to one or more ether ligand. The inventory of complexes is extensive. Common ether ligands are diethyl ether and tetrahydrofuran. Common chelating ether ligands include the glymes, dimethoxyethane (dme) and diglyme, and the crown ethers. Being lipophilic, metal-ether complexes often exhibit solubility in organic solvents, a property of interest in synthetic chemistry. In contrast, the di-ether 1,4-dioxane is generally a bridging ligand.

Transition metal complexes of thiocyanate describes coordination complexes containing one or more thiocyanate (SCN−) ligands. The topic also includes transition metal complexes of isothiocyanate. These complexes have few applications but played significant role in the development of coordination chemistry.

References

  1. ↑ Sharpe, A. G. The Chemistry of Cyano Complexes of the Transition Metals; Academic Press: London, 1976. ISBN   0-12-638450-9.
  2. ↑
    • Dunbar, K. R. and Heintz, R. A., "Chemistry of Transition Metal Cyanide Compounds: Modern Perspectives", Progress in Inorganic Chemistry, 1997, 45, 283-391.
  3. ↑ Eaton, Janice P.; Nicholls, David (1981). "The Complex Cyanides of Chromium(II) and Chromium(0)". Transition Metal Chemistry. 6 (4): 203–206. doi:10.1007/BF00618223. S2CID   96193332.
  4. ↑ Recent progress in transition metal hexacyanometallates: From structure to properties and functionality. 2022. Coordination Chemistry Reviews. 453/. Y. Avila, P. Acevedo-Peña, L. Reguera, E. Reguera. doi: 10.1016/j.ccr.2021.214274
  5. ↑ Brown, Leo D.; Raymond, Kenneth N. (1975). "Structural Characterization of the Pentacyanocobaltate(II) Anion in the Salt Tris(diethyldiisopropylammonium) Pentacyanocobaltate(II)". Inorganic Chemistry. 14 (11): 2590–2594. doi:10.1021/ic50153a002.
  6. ↑ Kwiatek, Jack (1968). "Reactions Catalyzed by Pentacyanocobaltate(II)". Catalysis Reviews. 1: 37–72. doi:10.1080/01614946808064700.
  7. ↑ Nitschke, Christian; Köckerling, Martin (March 2009). "A New Transition Metal Tetracyanidoborate: Synthesis, Structure and Properties of Co[B(CN) 4 ] 2 ·2H 2 O". Zeitschrift für anorganische und allgemeine Chemie. 635 (3): 503–507. doi:10.1002/zaac.200801234.
  8. 1 2 3 Smallwood, Zoe M.; Davis, Martin F.; Hill, J. Grant; James, Lara J. R.; Portius, Peter (April 2019). "Syntheses, Structures, and Infrared Spectra of the Hexa(cyanido) Complexes of Silicon, Germanium, and Tin". Inorganic Chemistry. 58 (7): 4583–4591. doi:10.1021/acs.inorgchem.9b00150. ISSN   0020-1669.
  9. 1 2 3 4 Nicholls, David; Ryan, T.Anthony (January 1980). "Complex cyanides of titanium". Inorganica Chimica Acta. 41: 233–237. doi:10.1016/S0020-1693(00)88461-3.
  10. 1 2 3 4 5 6 7 Chadwick, B.M.; Sharpe, A.G. (1966), "Transition Metal Cyanides and Their Complexes", Advances in Inorganic Chemistry and Radiochemistry, vol. 8, Elsevier, pp. 83–176, doi:10.1016/s0065-2792(08)60201-0, ISBN   978-0-12-023608-4 , retrieved 2024-01-21
  11. ↑ Buser, H. J.; Schwarzenbach, D.; Petter, W.; Ludi, A. (1977-11-01). "The crystal structure of Prussian Blue: Fe4[Fe(CN)6]3.xH2O". Inorganic Chemistry. 16 (11): 2704–2710. doi:10.1021/ic50177a008. ISSN   0020-1669.
  12. 1 2 3 Jach, Franziska; Wagner, Frank R.; Amber, Zeeshan H.; Rüsing, Michael; Hunger, Jens; Prots, Yurii; Kaiser, Martin; Bobnar, Matej; Jesche, Anton; Eng, Lukas M.; Ruck, Michael (2021-07-12). "Tricyanidoferrates(−IV) and Ruthenates(−IV) with Non-Innocent Cyanido Ligands". Angewandte Chemie International Edition. 60 (29): 15879–15885. doi:10.1002/anie.202103268. ISSN   1433-7851. PMC   8362014 . PMID   33938602.
  13. ↑ Dong, Wen; Wang, Chao; Ouyang, Yan; Liao, Dai-Zheng (March 2009). "Supramolecular Complexes Based on [M(CN) 8 ] 4- (M = Mo, W) and Aliphatic Amine Cu II Tectons". Zeitschrift für anorganische und allgemeine Chemie. 635 (3): 544–548. doi:10.1002/zaac.200801254.
  14. ↑ Kuchár, J.; Miklošová, M.; Černák, J.; Falvello, L.R. (August 2014). "Tetracyanidopalladates of Cu(II) with 2-aminoethylpyridines as blocking ligands: The role of the 2-aminoethyl arm position on the pyridine ring". Journal of Molecular Structure. 1072: 94–102. Bibcode:2014JMoSt1072...94K. doi:10.1016/j.molstruc.2014.04.061.
  15. 1 2 3 4 Arlt, Sören; Harloff, Jörg; Schulz, Axel; Stoffers, Alrik; Villinger, Alexander (5 December 2016). "Cyanido Antimonate(III) and Bismuthate(III) Anions". Inorganic Chemistry. 55 (23): 12321–12328. doi:10.1021/acs.inorgchem.6b02174. PMID   27934433.
  16. ↑ Birk, Francisco J.; Pinkowicz, Dawid; Dunbar, Kim R. (2016-09-12). "The Heptacyanotungstate(IV) Anion: A New 5 d Transition-Metal Member of the Rare Heptacyanometallate Family of Anions". Angewandte Chemie International Edition. 55 (38): 11368–11371. doi:10.1002/anie.201602949. hdl: 2027.42/137239 . ISSN   1433-7851.
  17. 1 2 3 Kobylarczyk, Jedrzej; Pinkowicz, Dawid; Srebro-Hooper, Monika; Hooper, James; Podgajny, Robert (2019-02-06). "Anion-π Architectures of HAT(CN) 6 and 5d Polycyanidometalates: [W(CN) 8 ] 3– , [Re(CN) 7 ] 3– , and [Pt(CN) 6 ] 2–". Crystal Growth & Design. 19 (2): 1215–1225. doi:10.1021/acs.cgd.8b01653. ISSN   1528-7483.
  18. ↑ Korkmaz, Şengül Aslan; Karadağ, Ahmet; Aydın, Ali; Yerli, Yusuf; Soylu, Mustafa Serkan (November 2016). "Binuclear cyanido complexes containing [Pt(CN)4]2− building block: Synthesis, crystal structures, magnetic properties and anticancer activities". Inorganica Chimica Acta. 453: 154–168. doi:10.1016/j.ica.2016.08.002.
  19. ↑ Matsushita, Nobuyuki; Noguchi, Wataru; Tanaka, Rikako (2017-03-28). "Potassium tetracyanidoaurate(III) monohydrate: a redetermination". IUCrData. 2 (3): x170382. Bibcode:2017IUCrD...270382M. doi: 10.1107/S2414314617003820 . ISSN   2414-3146.
  20. ↑ Fehlhammer, W. P. Fritz, M., "Emergence of a CNH and Cyano Complex Based Organometallic Chemistry", Chemical Reviews, 1993, volume 93, pp. 1243-80. doi : 10.1021/cr00019a016
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.