Nickel tetracarbonyl

Nickel carbonyl (IUPAC name: tetracarbonylnickel) is the organonickel compound with the formula Ni(CO)4. This colorless liquid is the principal carbonyl of nickel. It is an intermediate in the Mond process for producing very high-purity nickel and a reagent in organometallic chemistry, although the Mond Process has fallen out of common usage due to the health hazards in working with the compound. Nickel carbonyl is one of the most dangerous substances yet encountered in nickel chemistry due to its very high toxicity, compounded with high volatility and rapid skin absorption.[3]

Nickel tetracarbonyl
Nickel carbonyl
Nickel carbonyl
Names
IUPAC name
Tetracarbonylnickel
Other names
Nickel tetracarbonyl
Nickel carbonyl
Identifiers
3D model (JSmol)
6122797
ChEBI
ChemSpider
ECHA InfoCard 100.033.322
EC Number
  • 236-669-2
3135
RTECS number
  • QR6300000
UNII
UN number 1259
Properties
Ni(CO)4
Molar mass 170.73 g/mol
Appearance colorless liquid[1]
Odor musty,[1] like brick dust
Density 1.319 g/cm3
Melting point −17.2 °C (1.0 °F; 256.0 K)
Boiling point 43 °C (109 °F; 316 K)
0.018 g/100 mL (10 °C)
Solubility miscible in most organic solvents
soluble in nitric acid, aqua regia
Vapor pressure 315 mmHg (20 °C)[1]
Viscosity 3.05 x 10−4 Pa s
Structure
Tetrahedral
Tetrahedral
zero
Thermochemistry
320 J K−1 mol−1
−632 kJ/mol
−1180 kJ/mol
Hazards
Safety data sheet ICSC 0064
GHS pictograms
H225, H300, H310, H330, H351, H360D, H400, H410
P201, P202, P210, P233, P240, P241, P242, P243, P260, P271, P273, P280, P281, P284, P303+361+353, P304+340, P308+313, P310, P320, P370+378, P391, P403+233, P403+235, P405, P501
NFPA 704 (fire diamond)
Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineHealth code 4: Very short exposure could cause death or major residual injury. E.g. VX gasReactivity code 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g. hydrogen peroxideSpecial hazards (white): no code
3
4
3
Flash point 4 °C (39 °F; 277 K)
60 °C (140 °F; 333 K)
Explosive limits 2–34%
Lethal dose or concentration (LD, LC):
266 ppm (cat, 30 min)
35 ppm (rabbit, 30 min)
94 ppm (mouse, 30 min)
10 ppm (mouse, 10 min)[2]
360 ppm (dog, 90 min)
30 ppm (human, 30 min)
42 ppm (rabbit, 30 min)
7 ppm (mouse, 30 min)[2]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 0.001 ppm (0.007 mg/m3)[1]
REL (Recommended)
 TWA 0.001 ppm (0.007 mg/m3)[1]
IDLH (Immediate danger)
 Ca [2 ppm][1]
Related compounds
Iron pentacarbonyl
Dicobalt octacarbonyl
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Structure and bonding

In nickel tetracarbonyl, the oxidation state for nickel is assigned as zero. The formula conforms to 18-electron rule. The molecule is tetrahedral, with four carbonyl (carbon monoxide) ligands. Electron diffraction studies have been performed on this molecule, and the Ni–C and C–O distances have been calculated to be 1.838(2) and 1.141(2) angstroms respectively.[4]

Preparation

Ni(CO)4 was first synthesised in 1890 by Ludwig Mond by the direct reaction of nickel metal with CO.[5] This pioneering work foreshadowed the existence of many other metal carbonyl compounds, including those of V, Cr, Mn, Fe, and Co. It was also applied industrially to the purification of nickel by the end of the 19th century.[6]

At 323 K (50 °C; 122 °F), carbon monoxide is passed over impure nickel. The optimal rate occurs at 130 °C.[7]

Laboratory routes

Ni(CO)4 is not readily available commercially. It is conveniently generated in the laboratory by carbonylation of commercially available bis(cyclooctadiene)nickel(0).[8] It can also be prepared by reduction of ammoniacal solutions of nickel sulfate with sodium dithionite under an atmosphere of CO.[9]

Reactions
Spheres of nickel made by the Mond process

Thermal decarbonylation

On moderate heating, Ni(CO)4 decomposes to carbon monoxide and nickel metal. Combined with the easy formation from CO and even very impure nickel, this decomposition is the basis for the Mond process for the purification of nickel or plating onto surfaces. Thermal decomposition commences near 180 °C and increases at higher temperature.[7]

Reactions with nucleophiles and reducing agents

Like other low-valent metal carbonyls, Ni(CO)4 is susceptible to attack by nucleophiles. Attack can occur at nickel center, resulting in displacement of CO ligands, or at CO. Thus, donor ligands such as triphenylphosphine react to give Ni(CO)3(PPh3) and Ni(CO)2(PPh3)2. Bipyridine and related ligands behave similarly.[10] The monosubstitution of nickel tetracarbonyl with other ligands can be used to determine the Tolman electronic parameter, a measure of the electron donating or withdrawing ability of a given ligand.

Structure of Ni(PPh3)2(CO)2.

Treatment with hydroxides gives clusters such as [Ni5(CO)12]2− and [Ni6(CO)12]2−. These compounds can also be obtained by reduction of nickel carbonyl.

Thus, treatment of Ni(CO)4 with carbon nucleophiles (Nu−) results in acyl derivatives such as [Ni(CO)3C(O)Nu)]−.[11]

Reactions with electrophiles and oxidizing agents

Nickel carbonyl can be oxidized. Chlorine oxidizes nickel carbonyl into NiCl2, releasing CO gas. Other halogens behave analogously. This reaction provides a convenient method for precipitating the nickel portion of the toxic compound.

Reactions of Ni(CO)4 with alkyl and aryl halides often result in carbonylated organic products. Vinylic halides, such as PhCH=CHBr, are converted to the unsaturated esters upon treatment with Ni(CO)4 followed by sodium methoxide. Such reactions also probably proceed via oxidative addition. Allylic halides give the π-allylnickel compounds, such as (allyl)2Ni2Cl2:[12]

2 Ni(CO)4 + 2 ClCH2CH=CH2 → Ni2(μ-Cl)2(η3-C3H5)2 + 8 CO

Toxicology and safety considerations

The hazards of Ni(CO)4 are far greater than that implied by its CO content, reflecting the effects of the nickel if released in the body. Nickel carbonyl may be fatal if absorbed through the skin or more likely, inhaled due to its high volatility. Its LC50 for a 30-minute exposure has been estimated at 3 ppm, and the concentration that is immediately fatal to humans would be 30 ppm. Some subjects exposed to puffs up to 5 ppm described the odour as musty or sooty, but because the compound is so exceedingly toxic, its smell provides no reliable warning against a potentially fatal exposure.[13]

The vapours of Ni(CO)4 can autoignite. The vapor decomposes quickly in air, with a half-life of about 40 seconds.[14]

Nickel carbonyl poisoning is characterized by a two-stage illness. The first consists of headaches and chest pain lasting a few hours, usually followed by a short remission. The second phase is a chemical pneumonitis which starts after typically 16 hours with symptoms of cough, breathlessness and extreme fatigue. These reach greatest severity after four days, possibly resulting in death from cardiorespiratory or acute kidney injury. Convalescence is often extremely protracted, often complicated by exhaustion, depression and dyspnea on exertion. Permanent respiratory damage is unusual. The carcinogenicity of Ni(CO)4 is a matter of debate, but is presumed to be significant.

It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.[15]

"Requiem for the Living" (1978), an episode of Quincy, M.E., features a poisoned, dying crime lord who asks Dr. Quincy to autopsy his still-living body. Quincy identifies the poison—nickel carbonyl.

References
  1. NIOSH Pocket Guide to Chemical Hazards. "#0444". National Institute for Occupational Safety and Health (NIOSH).
  2. "Nickel carbonyl". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  3. The Merck Index (7th ed.). Merck.
  4. Hedberg, L.; Iijima, T.; Hedberg, K. (1979). "Nickel tetracarbonyl, Ni(CO)4. I. Molecular Structure by Gaseous Electron Diffraction. II. Refinement of Quadratic Force Field". The Journal of Chemical Physics. 70 (7): 3224–3229. doi:10.1063/1.437911.
  5. Mond, L.; Langer, C.; Quincke, F. (1890). "Action of Carbon Monoxide on Nickel". J. Chem. Soc. Trans. 57: 749–753. doi:10.1039/CT8905700749.
  6. "The Extraction of Nickel from its Ores by the Mond Process". Nature. 59 (1516): 63–64. 1898. doi:10.1038/059063a0.
  7. Lascelles, K.; Morgan, L. G.; Nicholls, D.; Beyersmann, D. "Nickel Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a17_235.pub2.
  8. Jolly, P. W. (1982). "Nickel Tetracarbonyl". In Abel, Edward W.; Stone, F. Gordon A.; Wilkinson, Geoffrey (eds.). Comprehensive Organometallic Chemistry. I. Oxford: Pergamon Press. ISBN 0-08-025269-9.
  9. F. Seel (1963). "Nickel Carbonyl". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry. 2 (2nd ed.). NY: Academic Press. pp. 1747–1748.
  10. Elschenbroich, C.; Salzer, A. (1992). Organometallics: A Concise Introduction (2nd ed.). Weinheim: Wiley-VCH. ISBN 3-527-28165-7.
  11. Pinhas, A. R. (2003). "Tetracarbonylnickel". Encyclopedia of Reagents for Organic Synthesis, 8 Volume Set. Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. doi:10.1002/047084289X.rt025m. ISBN 0471936235.
  12. Semmelhack, M. F.; Helquist, P. M. (1972). "Reaction of Aryl Halides with π-Allylnickel Halides: Methallylbenzene". Organic Syntheses. 52: 115.; Collective Volume, 6, p. 722
  13. Board on Environmental Studies and Toxicology (2008). "Nickel Carbonyl: Acute Exposure Guideline Levels". Acute Exposure Guideline Levels for Selected Airborne Chemicals. 6. National Academies Press. pp. 213–259.
  14. Stedman, D. H.; Hikade, D. A.; Pearson, R. Jr.; Yalvac, E. D. (1980). "Nickel Carbonyl: Decomposition in Air and Related Kinetic Studies". Science. 208 (4447): 1029–1031. doi:10.1126/science.208.4447.1029. PMID 17779026.
  15. "40 C.F.R.: Appendix A to Part 355—The List of Extremely Hazardous Substances and Their Threshold Planning Quantities" (PDF) (July 1, 2008 ed.). Government Printing Office. Archived from the original (PDF) on February 25, 2012. Retrieved October 29, 2011. Cite journal requires |journal= (help)

Further reading
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