Transition metal nitrile complexes

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[Cu(MeCN)4] , often encountered as its PF6 salt, is a common transition metal nitrile complex. Tetrakis(acetonitrile)copper(I) hexafluorophosphate.png
[Cu(MeCN)4] , often encountered as its PF6 salt, is a common transition metal nitrile complex.

Transition metal nitrile complexes are coordination compounds containing nitrile ligands. Because nitriles are weakly basic, the nitrile ligands in these complexes are often labile. [1]

Contents

Scope of nitriles

Typical nitrile ligands are acetonitrile, propionitrile, and benzonitrile. The structures of [Ru(NH3)5(NCPh)]n+ have been determined for the 2+ and 3+ oxidation states. Upon oxidation the Ru-NH3 distances contract and the Ru-NCPh distances elongate, consistent with amines serving as pure-sigma donor ligands and nitriles functioning as pi-acceptors. [2]

Structural comparisons of [Ru(NH3)5(NCPh)] for 2+ and 3+ salts (distance in picometers) A5Ru(NCPh).png
Structural comparisons of [Ru(NH3)5(NCPh)] for 2+ and 3+ salts (distance in picometers)

Synthesis and reactions

Acetonitrile, propionitrile and benzonitrile are also popular solvents. Because nitrile solvents have high dielectric constants, cationic complexes containing a nitrile ligand are often soluble in a solution of that nitrile.

Some complexes can be prepared by dissolving an anhydrous metal salt in the nitrile. In other cases, a suspension of the metal is oxidized with a solution of NOBF4 in the nitrile: [3]

Ni + 6 MeCN + 2 NOBF4 → [Ni(MeCN)6](BF4)2 + 2 NO

Heteroleptic complexes of molybdenum and tungsten can by synthesized from their respective hexacarbonyl complexes. [4]

M(CO)6 + 4 MeCN + 2 NOBF4 → [M(NO)2(MeCN)4](BF4)2
Portion of the structure of the tetrachlorozincate (ZnCl4 ) salt of [Ni(MeCN)6] ACNNIZ.png
Portion of the structure of the tetrachlorozincate (ZnCl4 ) salt of [Ni(MeCN)6]

For the synthesis of some acetonitrile complexes, the nitrile serves as a reductant. This method is illustrated by the conversion of molybdenum pentachloride to the molybdenum(IV) complex: [6]

2 MoCl5 + 5 CH3CN → 2 MoCl4(CH3CN)2 + ClCH2CN + HCl

Reactions

Transition metal nitrile complexes are usually employed because the nitrile ligand is labile and relatively chemically inert. Cationic nitrile complexes are however susceptible to nucleophilic attack at carbon. Consequently some nitrile complexes catalyze the hydrolysis of nitriles to give the amides. [7]

Fe- and Co-nitrile complexes are intermediates in nitrile hydratase enzymes. N-coordination activates the sp-hybridized carbon center toward attack by nucleophiles, including water. [8] [9] Thus coordination of the nitrile to a cationic metal center is the basis for the catalytic hydration:

M-NCR + H2O → M-O=C(NH2)R
M-O=C(NH2)R + NCR → O=C(NH2)R + M-NCR

Nitrile ligands in electron-rich complexes are susceptible to oxidation, e.g. by iodosylbenzene. [10] Nitriles undergo coupling with alkenes, also involving electron-rich complexes. [11]

Examples

[M(NCMe)6]n+

[M(NCMe)4]n+

[M(NCMe)4 or 5]2n+

[M(NCMe)2]+

Mixed ligand examples

Complexes of η2-nitrile ligands

In some of its complexes, nitriles function as η2-ligands. This bonding mode is more common for complexes of low-valence metals, such as Ni(0). Complexes of η2-nitriles are expected to form as transient intermediates in certain metal-catalyzed reactions of nitriles, such as the Hoesch reaction and the hydrogenation of nitriles. In some cases, η2-nitrile ligands are intermediates that preceded oxidative addition. [29]

Structure of Ni(diphosphine)(e -PhCN) ACEKAU.png
Structure of Ni(diphosphine)(η -PhCN)

See also

Related Research Articles

Anions that interact weakly with cations are termed non-coordinating anions, although a more accurate term is weakly coordinating anion. Non-coordinating anions are useful in studying the reactivity of electrophilic cations. They are commonly found as counterions for cationic metal complexes with an unsaturated coordination sphere. These special anions are essential components of homogeneous alkene polymerisation catalysts, where the active catalyst is a coordinatively unsaturated, cationic transition metal complex. For example, they are employed as counterions for the 14 valence electron cations [(C5H5)2ZrR]+ (R = methyl or a growing polyethylene chain). Complexes derived from non-coordinating anions have been used to catalyze hydrogenation, hydrosilylation, oligomerization, and the living polymerization of alkenes. The popularization of non-coordinating anions has contributed to increased understanding of agostic complexes wherein hydrocarbons and hydrogen serve as ligands. Non-coordinating anions are important components of many superacids, which result from the combination of Brønsted acids and Lewis acids.

<span class="mw-page-title-main">Palladium(II) chloride</span> Chemical compound

Palladium(II) chloride, also known as palladium dichloride and palladous chloride, are the chemical compounds with the formula PdCl2. PdCl2 is a common starting material in palladium chemistry – palladium-based catalysts are of particular value in organic synthesis. It is prepared by the reaction of chlorine with palladium metal at high temperatures.

<span class="mw-page-title-main">Molybdenum(V) chloride</span> Chemical compound

Molybdenum(V) chloride is the inorganic compound with the empirical formula MoCl5. This dark volatile solid is used in research to prepare other molybdenum compounds. It is moisture-sensitive and soluble in chlorinated solvents.

<span class="mw-page-title-main">Sandwich compound</span> Chemical compound made of two ring ligands bound to a metal

In organometallic chemistry, a sandwich compound is a chemical compound featuring a metal bound by haptic, covalent bonds to two arene (ring) ligands. The arenes have the formula CnHn, substituted derivatives and heterocyclic derivatives. Because the metal is usually situated between the two rings, it is said to be "sandwiched". A special class of sandwich complexes are the metallocenes.

<span class="mw-page-title-main">Tungsten hexacarbonyl</span> Chemical compound

Tungsten hexacarbonyl (also called tungsten carbonyl) is an organometallic compound with the formula W(CO)6. This complex gave rise to the first example of a dihydrogen complex.

<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.

<span class="mw-page-title-main">Molybdenum tetrachloride</span> Chemical compound

Molybdenum tetrachloride is the inorganic compound with the empirical formula MoCl4. The material exists as two polymorphs, both being dark-colored paramagnetic solids. These compounds are mainly of interest as precursors to other molybdenum complexes.

<span class="mw-page-title-main">Sodium tetraphenylborate</span> Chemical compound

Sodium tetraphenylborate is the organic compound with the formula NaB(C6H5)4. It is a salt, wherein the anion consists of four phenyl rings bonded to boron. This white crystalline solid is used to prepare other tetraphenylborate salts, which are often highly soluble in organic solvents. The compound is used in inorganic and organometallic chemistry as a precipitating agent for potassium, ammonium, rubidium, and caesium ions, and some organic nitrogen compounds.

<span class="mw-page-title-main">Tetrakis(acetonitrile)copper(I) hexafluorophosphate</span> Chemical compound

Tetrakis(acetonitrile)copper(I) hexafluorophosphate is a salt with the formula [Cu(CH3CN)4]PF6. It is a colourless solid that is used in the synthesis of other copper complexes. The cation [Cu(CH3CN)4]+ is a well-known example of a transition metal nitrile complex.

<span class="mw-page-title-main">Sodium tetrachloropalladate</span> Chemical compound

Sodium tetrachloropalladate is an inorganic compound with the chemical formula Na2PdCl4. This salt, and the analogous alkali metal salts of the form M2PdCl4, may be prepared simply by reacting palladium(II) chloride with the appropriate alkali metal chloride in aqueous solution. Palladium(II) chloride is insoluble in water, whereas the product dissolves:

<span class="mw-page-title-main">Tetrakis(3,5-bis(trifluoromethyl)phenyl)borate</span> Chemical compound

Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate is an anion with chemical formula [{3,5-(CF3)2C6H3}4B]−, which is commonly abbreviated as [BArF4]−, indicating the presence of fluorinated aryl (ArF) groups. It is sometimes referred to as Kobayashi's anion in honour of Hiroshi Kobayashi who led the team that first synthesised it. More commonly it is affectionately nicknamed "BARF." The BARF ion is also abbreviated BArF24−, to distinguish it from the closely related BArF−
20, [(C6F5)4B]−. However, for a small group of chemists, the anion is abbreviated as TFPB otherwise, short for Tetrakis[3,5-bis(triFluoromethyl)Phenyl]Borate.

In organometallic chemistry, bent metallocenes are a subset of metallocenes. In bent metallocenes, the ring systems coordinated to the metal are not parallel, but are tilted at an angle. A common example of a bent metallocene is Cp2TiCl2. Several reagents and much research is based on bent metallocenes.

<span class="mw-page-title-main">Brookhart's acid</span> Chemical compound

Brookhart's acid is the salt of the diethyl ether oxonium ion and tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BAr′4). It is a colorless solid, used as a strong acid. The compound was first reported by Volpe, Grant, and Brookhart in 1992.

<span class="mw-page-title-main">Molybdenum(III) chloride</span> Chemical compound

Molybdenum(III) chloride is the inorganic compound with the formula MoCl3. It forms purple crystals.

<span class="mw-page-title-main">Bis(dinitrogen)bis(1,2-bis(diphenylphosphino)ethane)molybdenum(0)</span> Chemical compound

trans-Bis(dinitrogen)bis[1,2-bis(diphenylphosphino)ethane]molybdenum(0) is a coordination complex with the formula Mo(N2)2(dppe)2. It is a relatively air stable yellow-orange solid. It is notable as being the first discovered dinitrogen containing complex of molybdenum.

<span class="mw-page-title-main">Bis(benzonitrile)palladium dichloride</span> Chemical compound

Bis(benzonitrile)palladium dichloride is the coordination complex with the formula PdCl2(NCC6H5)2. It is the adduct of two benzonitrile (PhCN) ligands with palladium(II) chloride. It is a yellow-brown solid that is soluble in organic solvents. The compound is a reagent and a precatalyst for reactions that require soluble Pd(II). A closely related compound is bis(acetonitrile)palladium dichloride.

<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 dithiocarbamate complexes</span>

Transition metal dithiocarbamate complexes are coordination complexes containing one or more dithiocarbamate ligand, which are typically abbreviated R2dtc−. Many complexes are known. Several homoleptic derivatives have the formula M(R2dtc)n where n = 2 and 3.

<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.

References

  1. ↑ Rach, S. F.; Kühn, F. E. (2009). "Nitrile Ligated Transition Metal Complexes with Weakly Coordinating Counteranions and Their Catalytic Applications". Chemical Reviews. 109 (5): 2061–2080. doi:10.1021/cr800270h. PMID   19326858.
  2. ↑ Shin, Yeung-gyo K.; Szalda, David J.; Brunschwig, Bruce S.; Creutz, Carol; Sutin, Norman (1997). "Electronic and Molecular Structures of Pentaammineruthenium Pyridine and Benzonitrile Complexes as a Function of Oxidation State". Inorganic Chemistry. 36 (14): 3190–3197. doi:10.1021/ic9700967. PMID   11669976.
  3. ↑ Heintz, Robert A.; Smith, Jennifer A.; Szalay, Paul S.; Weisgerber, Amy; Dunbar, Kim R. (2002). "Homoleptic Transition Metal Acetonitrile Cations with Tetrafluoroborate or Trifluoromethanesulfonate Anions". Inorg. Synth. 33: 75–83. doi:10.1002/0471224502.ch2.
  4. ↑ Thomas, Richard R.; Sen, Ayusman (2007). "Acetonitrile Complexes of Selected Transition Metal Cations". Inorganic Syntheses . 28: 63–67. doi:10.1002/9780470132593.ch14. ISBN   9780470132593.
  5. ↑ I. Sotofte; R. G. Hazell; S. E. Rasmussen (1976). "Hexaacetonitrilenickel(II) Tetrachlorozincate. A Crystal Structure with Serious Overlap in the Patterson Function". Acta Crystallographica Section B. 32 (6): 1692–1696. doi: 10.1107/S0567740876006249 .
  6. ↑ Maria, Sébastien; Poli, Rinaldo (2014). "Ether Complexes of Molybdenum(III) and Molybdenum(IV) chlorides". Inorganic Syntheses: Volume 36 (PDF). Inorganic Syntheses. Vol. 36. pp. 15–18. doi:10.1002/9781118744994.ch03. ISBN   9781118744994.
  7. ↑ Pombeiro, A.J.L.; Kukushkin, V.Yu. (2003). "Reactivity of Coordinated Nitriles". Comprehensive Coordination Chemistry II. pp. 639–660. doi:10.1016/B0-08-043748-6/01248-2. ISBN   9780080437484.
  8. ↑ Curtis, Neville J.; Sargeson, Alan M. (1984). "Synthesis and base hydrolysis of pentaammine N,N-dimethylformamide and acetonitrile complexes of rhodium(III) and iridium(III)". Journal of the American Chemical Society. 106 (3): 625–630. doi:10.1021/ja00315a029.
  9. ↑ Kovacs, Julie A. (2004). "Synthetic Analogues of Cysteinate-Ligated Non-Heme Iron and Non-Corrinoid Cobalt Enzymes". Chemical Reviews. 104 (2): 825–848. doi:10.1021/cr020619e. PMC   4487544 . PMID   14871143.
  10. ↑ Cross, Jeffrey L.; Garrett, Andrew D.; Crane, Todd W.; White, Peter S.; Templeton, Joseph L. (2004). "Coordination and reactivity of acetonitrile in tungsten(IV) complexes: Oxidation, methylation and dimerization of coordinated acetonitrile". Polyhedron. 23 (17): 2831–2840. doi:10.1016/j.poly.2004.09.008.
  11. ↑ Cohen, Steven A.; Bercaw, John E. (1985). "Titanacycles derived from reductive coupling of nitriles, alkynes, acetaldehyde, and carbon dioxide with bis(pentamethylcyclopentadienyl)(ethylene)titanium(II)". Organometallics. 4 (6): 1006–1014. doi:10.1021/om00125a008.
  12. ↑ Clemente, Dore Augusto (2005). "A Study of the 8466 Structures Reported in Inorganica Chimica Acta: 52 Space Group Changes and Their Chemical Consequences". Inorganica Chimica Acta. 358 (6): 1725–1748. doi:10.1016/j.ica.2004.10.037.
  13. ↑ Thangavel, Arumugam; Wieliczko, Marika; Scarborough, Christopher; Dittrich, Birger; Bacsa, John (2015). "An Investigation of the Electron Density of a Jahn–Teller-Distorted CrII Cation: The Crystal Structure and Charge Density of Hexakis(acetonitrile-κN)chromium(II) Bis(tetraphenylborate) Acetonitrile Disolvate". Acta Crystallographica Section C: Structural Chemistry. 71 (11): 936–943. doi:10.1107/S2053229615015739. PMID   26524164.
  14. ↑ Hatlevik, Øyvind; Arif, Atta M.; Miller, Joel S. (2004). "Synthesis and Characterization of Hexakis(acetonitrile)chromium(III) Tetrafluoroborate, [CrIII(NCMe)6][BF4]3. A Nonaqueous CrIII Source". Journal of Physics and Chemistry of Solids. 65: 61–63. doi:10.1016/j.jpcs.2003.08.020.
  15. ↑ Musgrave, Rebecca A.; Hailes, Rebekah L. N.; Schäfer, André; Russell, Andrew D.; Gates, Paul J.; Manners, Ian (2018). "New Reactivity at the Silicon Bridge in Sila[1]ferrocenophanes" (PDF). Dalton Transactions. 47 (8): 2759–2768. doi:10.1039/C7DT04593J. hdl: 1983/9e6d6454-2797-41d2-a75f-ed90363b5bed . PMID   29417116. S2CID   3406313.
  16. ↑ Hijazi, Ahmed K.; Al Hmaideen, Akef; Syukri, Syukri; Radhakrishnan, Narayanan; Herdtweck, Eberhardt; Voit, Brigitte; Kühn, Fritz E. (2008). "Synthesis and Characterization of Acetonitrile-Ligated Transition-Metal Complexes with Tetrakis(pentafluorophenyl)borate as Counteranions". European Journal of Inorganic Chemistry. 2008 (18): 2892–2898. doi: 10.1002/ejic.200800201 .
  17. ↑ Hijazi, Ahmed K.; Yeong, Hui Y.; Zhang, Yanmei; Herdtweck, Eberhardt; Nuyken, Oskar; Kühn, Fritz E. (2007). "Isobutene Polymerization Using [CuII(NCMe)6]2+ with Non-Coordinating Anions as Catalysts". Macromolecular Rapid Communications. 28 (5): 670–675. doi:10.1002/marc.200600139.
  18. ↑ Underwood, Christopher C.; Stadelman, Bradley S.; Sleeper, Mark L.; Brumaghim, Julia L. (2013). "Synthesis and Electrochemical characterization of [Ru(NCCH3)6]2+, Tris(acetonitrile) Tris(pyrazolyl)borate, and Tris(acetonitrile) Tris(pyrazolyl)methane Ruthenium(II) Complexes". Inorganica Chimica Acta. 405: 470–476. doi:10.1016/j.ica.2013.02.027.
  19. 1 2 Prater, M. E.; Pence, L. E.; Clérac, R.; Finniss, G. M.; Campana, C.; Auban-Senzier, P.; Jérome, D.; Canadell, E.; Dunbar, K. R. (1999). "A Remarkable Family of Rhodium Acetonitrile Compounds Spanning Three Oxidation States and with Nuclearities Ranging from Mononuclear and Dinuclear to One-Dimensional Chains". Journal of the American Chemical Society. 121 (35): 8005–8016. doi:10.1021/ja991130e.
  20. 1 2 Bolliger, Robin; Blacque, Olivier; Braband, Henrik; Alberto, Roger (2022). "One Electron Changes Everything: Synthesis, Characterization, and Reactivity Studies of [Re(NCCH3)6]3+". Inorganic Chemistry. 61 (46): 18325–18334. doi:10.1021/acs.inorgchem.2c02056. PMC   9682483 . PMID   36169602. S2CID   252565929.
  21. ↑ Henriques, Rui T.; Herdtweck, Eberhardt; Kühn, Fritz E.; Lopes, André D.; Mink, Janos; Romão, Carlos C. (1998). "Synthesis, characterization, and reactions of tetrakis(nitrile)chromium(II) tetrafluoroborate complexes †". Journal of the Chemical Society, Dalton Transactions (8): 1293–1298. doi:10.1039/A708988K.
  22. ↑ Thomas, Richard R.; Sen, Ayusman (1990). "Acetonitrile Complexes of Selected Transition Metal Cations". Inorganic Syntheses. Inorganic Syntheses. pp. 63–67. doi:10.1002/9780470132593.ch14. ISBN   9780470132593.
  23. ↑ Cotton, F. Albert.; Wiesinger, Kenneth J. (1991). "Synthesis and characterization of octaacetonitriledimolybdenum(II) tetrafluoroborate". Inorganic Chemistry. 30 (4): 871–873. doi:10.1021/ic00004a055.
  24. ↑ Bryan, Jeffrey C.; Cotton, F. Albert; Daniels, Lee M.; Haefner, Steven C.; Sattelberger, Alfred P. (1995). "Preparation and Characterization of the Fully Solvated Ditechnetium Cation [Tc2(CH3CN)10]4+". Inorganic Chemistry. 34 (7): 1875–1883. doi:10.1021/ic00111a040.
  25. ↑ Bera, Jitendra K.; Schelter, Eric J.; Patra, Sanjib K.; Bacsa, John; Dunbar, Kim R. (2006). "Syntheses and Reactivity Studies of Solvated Dirhenium Acetonitrile Complexes". Dalton Transactions (33): 4011–9. doi:10.1039/b601463a. PMID   17028710.
  26. ↑ Zhang, Yanmei; Santos, Ana M.; Herdtweck, Eberhardt; Mink, Janos; Kühn, Fritz E. (2005). "Organonitrile ligated silver complexes with perfluorinated weakly coordinating anions and their catalytic application for coupling reactions" (PDF). New J. Chem. 29 (2): 366–370. doi:10.1039/b414060e.
  27. ↑ Willner, H.; Schaebs, J.; Hwang, G.; Mistry, F.; Jones, R.; Trotter, J.; Aubke, F. (1992). "Bis(carbonyl)gold(I) undecafluorodiantimonate(V), [Au(CO)2][Sb2F11]: Synthesis, vibrational, and carbon-13 NMR study and the molecular structure of bis(acetonitrile)gold(I) hexafluoroantimonate(V), [Au(NCCH3)2][SbF6]". Journal of the American Chemical Society. 114 (23): 8972–8980. doi:10.1021/ja00049a030.
  28. ↑ Kubas, Gregory J.; van der Sluys, Lori Stepan (1990). "Tricarbonyltris(Nitrile) Complexes of Cr, Mo, and W". Inorganic Syntheses. Inorganic Syntheses. Vol. 28. pp. 29–33. doi:10.1002/9780470132593.ch6. ISBN   9780470132593.
  29. ↑ Churchill, D.; Shin, J. H.; Hascall, T.; Hahn, J. M.; Bridgewater, B. M.; Parkin, G. (1999). "The Ansa Effect in Permethylmolybdenocene Chemistry: A [Me2Si] Ansa Bridge Promotes Intermolecular C−H and C−C Bond Activation". Organometallics. 18 (13): 2403–2406. doi:10.1021/om990195n.
  30. ↑ García, J. J.; Arévalo, A.; Brunkan, N. M.; Jones, W. D. (2004). "Cleavage of Carbon−Carbon Bonds in Alkyl Cyanides Using Nickel(0)". Organometallics. 23 (16): 3997–4002. doi:10.1021/om049700t.
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