Nickel tetracarbonyl | |
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Tetracarbonylnickel |
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Other names
Nickel carbonyl |
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Identifiers | |
CAS number | 13463-39-3 |
PubChem | 26039 |
ChemSpider | 21865021 |
EC number | 236-669-2 |
UN number | 1259 |
ChEBI | CHEBI:30372 |
RTECS number | QR6300000 |
Jmol-3D images | Image 1 |
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Properties | |
Molecular formula | Ni(CO)4 |
Molar mass | 170.73 g/mol |
Appearance | colorless or very-pale-yellow 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 ΔfH |
−632 kJ/mol |
Std enthalpy of combustion ΔcH |
−1180 kJ/mol |
Standard molar entropy S |
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
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Flash point | 4 °C |
Autoignition temperature |
60 °C |
Explosive limits | 2–34% |
Related compounds | |
Related metal carbonyls | Iron pentacarbonyl Dicobalt octacarbonyl |
(verify) (what is: / ?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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Infobox references |
Nickel carbonyl (IUPAC name: tetracarbonylnickel) is the organonickel compound with the formula Ni(CO)4. This pale-yellow liquid is the principal carbonyl of nickel. It is an intermediate in the Mond process for the purification of nickel and a reagent in organometallic chemistry. Nickel carbonyl is the most toxic substance encountered in industrial processes.[1]
Contents |
Nickel tetracarbonyl contains nickel in the zero oxidation state. It has 18 valence electron, and is a tetrahedral molecule with four carbonyl (carbon monoxide) ligands attached to nickel. 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. 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.[2]
Ni(CO)4 was first synthesised in 1890 by Ludwig Mond by the direct reaction of nickel metal with CO.[3] 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.[4]
At 323 K (50 °C (122 °F)), carbon monoxide is passed over impure nickel. The optimal rate occurs at 130 °C.[5]
Ni(CO)4 is not readily available commercially. It is conveniently generated in the laboratory by carbonylation of commercially available bis(cyclooctadiene)nickel(0).
On moderate heating, Ni(CO)4 decomposes to carbon monoxide and nickel metal. Combined with the easy formation from CO and even impure nickel, this decomposition is the basis for the Mond process for the purification of nickel. Thermal decomposition commences near 180 °C and increases at higher temperature[5]
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.[6] 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.
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)]−.[7]
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 destroying unwanted portions 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 pi-allyl nickel compounds, such as (allyl)2Ni2Cl2:[8]
Ni(CO)4 is highly hazardous, much more so than implied by its CO content, reflecting the effects of the nickel if it were 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.[9] 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 poison.
Human systemic effects by inhalation: somnolence, fever, and other pulmonary changes. Vapors may cause coughing, dyspnea (difficult breathing), irritation, congestion and edema of the lungs, tachycardia (rapid pulse), cyanosis, headache, dizziness, and weakness. Toxicity by inhalation is believed to be caused by both the nickel and carbon monoxide liberated in the lungs. Chronic exposure may cause cancer of lungs or nasal sinuses. Sensitization dermatitis is fairly common. It is considered the most hazardous compound of nickel in the workplace. It is lipid soluble and can cross biological membranes (e.g., lung alveolus, blood-brain barrier, placental barrier).
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.
Nickel carbonyl vapor decomposes quickly in air, lasting only about a minute.[10]
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