Nickel tetracarbonyl

Nickel tetracarbonyl
IUPAC name	Tetracarbonylnickel
Other names	Nickel carbonyl
Identifiers
CAS number	13463-39-3 Y
PubChem	26039
EC number	236-669-2
UN number	1259
ChEBI	30372
RTECS number	QR6300000
Properties
Molecular formula	Ni(CO)4
Molar mass	170.73 g/mol
Appearance	colorless liquid diamagnetic
Density	1.319 g/cm3
Melting point	-17.2 °C, 256 K, 1 °F
Boiling point	43 °C, 316 K, 109 °F
Solubility in water	.018 g/100 mL (10 °C)
Solubility	miscible in most organic solvents soluble in nitric acid, aqua regia
Viscosity	3.05 x 10-4 Pa s
Structure
Coordination geometry	Tetrahedral
Molecular shape	Tetrahedral
Dipole moment	zero
Thermochemistry
Std enthalpy of formation ΔfHo298	−632 kJ/mol
Std enthalpy of combustion ΔcHo298	−1180 kJ/mol
Standard molar entropy So298	320 J K−1 mol−1
Hazards
MSDS	ICSC 0064
EU Index	028-001-00-1
EU classification	Flammable ('F) Carc. Cat. 3 Repr. Cat. 2 Very Toxic (T+) Dangerous for the environment (N)
R-phrases	R61, R11, R26, R40, R50/53
S-phrases	S53, S45, S60, S61
NFPA 704	3 4 3
Flash point	4 °C
Autoignition temperature	60 °C
Explosive limits	2–34%
Related compounds
Related metal carbonyls	Iron pentacarbonyl Dicobalt octacarbonyl
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Nickel carbonyl (IUPAC name: tetracarbonylnickel) is a colorless organometallic complex that is a versatile reagent, first described in 1890 by Ludwig Mond. It was the first metal simple carbonyl complex to be reported. Its volatility at room temperature and toxicity have earned the compound the nickname "liquid death."

Structure and bonding

Having the molecular formula Ni(CO)₄, nickel carbonyl is composed of a central nickel atom surrounded by four carbonyl (carbon monoxide) ligands in a tetrahedral arrangement. The CO ligands, in which the C and the O are connected by triple bonds (often depicted as double bonds), are covalently bonded to the nickel atom via the carbon ends. The structures of these compounds baffled chemists for many years, and most publications before 1950 depicted chains of CO chelated to the metal.

Nickel carbonyl has 18 valence electrons, like many other metal carbonyls such as iron pentacarbonyl and molybdenum hexacarbonyl. These metal carbonyls have symmetrical structures and are charge-neutral, resulting in their high volatility. In Ni(CO)₄, the nickel atom has a formal oxidation number of zero.

Preparation

Ni(CO)₄ was first synthesised in 1890 by Ludwig Mond by the direct reaction of nickel metal with CO. This pioneering work foreshadowed the existence of many other metal carbonyl compounds, including those of V, Cr, Mn, Fe, and Co.

At 323 K (50 °C (122 °F)), carbon monoxide is passed over impure nickel. On moderate heating, such as contact with a hot glass surface, Ni(CO)₄ decomposes back to carbon monoxide and nickel metal. These two reactions form the basis for the Mond process for the purification of nickel.^[1]

Chemical reactions

Like other low-valent metal carbonyls, Ni(CO)₄ undergoes CO substitution reactions and can be oxidized. Donor ligands such as triphenylphosphine react to give Ni(CO)₃(PPh₃) and Ni(CO)₂(PPh₃)₂(bipy) and related ligands behave similarly.

Chlorine oxidizes nickel carbonyl into NiCl₂, releasing CO gas. Other halogens behave analogously. This reaction provides a convenient method for destroying unwanted portions of the toxic compound.

Reduction or treatment with hydroxides brings about clusters such as [Ni₅(CO)₁₂]²⁻ and [Ni₆(CO)₁₂]²⁻.

Reactions of Ni(CO)₄ with alkyl and aryl halides often result in carbonylated organic products. Vinyl 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 Ni(CO)₃, which undergoes oxidative addition.

Metal carbonyls are also susceptible to attack by nucleophiles. Thus, treatment of Ni(CO)₄ with some nucleophiles (Nu⁻) results in acyl derivatives including [Ni(CO)₃C(O)Nu)]⁻.

Toxicology and safety considerations

Ni(CO)₄ is highly hazardous, much more so than implied by its CO content, reflecting the effects of the nickel if it was 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 since the compound is so exceedingly toxic its smell provides no reliable warning against a potentially fatal exposure. [1] Historically, laboratories that used Ni(CO)₄ would keep a canary in the lab as an indicator of nickel carbonyl toxicity, due to the higher sensitivity of birds to this toxin.^{[citation needed]}

The vapours of Ni(CO)₄ can autoignite.

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 renal failure. 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.

External links

• International Chemical Safety Card 0064
• National Pollutant Inventory - Nickel carbonyl fact sheet
• NIOSH Pocket Guide to Chemical Hazards
• European Chemicals Bureau
• IARC Monograph "Nickel and Nickel compounds"
• NIST Standard Reference Database

References

1. ^ Mond, L; Langer, K; Quincke, F (1890). "Action of carbon monoxide on nickel". J. Chem. Soc. 57: 749–53. doi:10.1039/CT8905700749. 

• Lascelles,Keith; Morgan, Lindsay G.; & Nicholls, David (1991). "Nickel Compounds". Ullmann's Encyclopedia of Industrial Chemistry A17 (5): 235–249. 
• EROS Encyclopedia of Reagents for Organic Synthesis, John Wiley & Sons, 2003.
• C. Elschenbroich, A. Salzer ”Organometallics : A Concise Introduction” (2nd Ed) (1992) from Wiley-VCH: Weinheim. ISBN 3-527-28165-7
• Shi Z (1991). "Nickel carbonyl: toxicity and human health". The Science of The Total Environment 148: 293–298. doi:10.1016/0048-9697(94)90406-5. DOI
• Sunderman FW (1989). "A Pilgrimage into the Archive of Nickel Toxicology". Annals of Clinical and Lalboratory Science 19: 1–16. 
• Armit HW (1908). "The toxicology of nickel carbonyl. Part II.". Journal of Hygiene 8: 565–610. 
• Armit HW (1907). "The toxicology of nickel carbonyl". Journal of Hygiene 7: 525–551. 
• Barceloux DG (1999). "Nickel". Journal of Toxicology-Clinical Toxicology 37: 239–258. doi:10.1081/CLT-100102423.  DOI