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Dicobalt octacarbonyl
Co 2 CO )8 hexanes
Names
IUPAC name
Octacarbonyldicobalt(Co—Co )
Other names
Cobalt carbonyl (2:8), di-mu-Carbonylhexacarbonyldicobalt, Cobalt octacarbonyl, Cobalt tetracarbonyl dimer, Dicobalt carbonyl, Octacarbonyldicobalt
Identifiers
CAS Number
3D model (JSmol )
Interactive image
ChemSpider
ECHA InfoCard 100.030.454
EC Number
PubChem CID
RTECS number
UNII
UN number
3281
CompTox Dashboard (EPA )
InChI=1S/8CO.2Co/c8*1-2;;/q;;;;;;;;2*+2 Y
Key: MQIKJSYMMJWAMP-UHFFFAOYSA-N Y
InChI=1/8CO.2Co/c8*1-2;;/q;;;;;;;;2*+2
Key: MQIKJSYMMJWAMP-UHFFFAOYAG
O=C=[Co ]1(=C=O)(=C=O)C(=O)[Co ](=C=O)(=C=O)(=C=O)C1=O
O=C=[Co-4](=C=O)(=C=O)(=C=O)[Co-4](=C=O)(=C=O)(=C=O)=C=O
Properties
Chemical formula
Co 2 CO )8
Molar mass
341.95 g/mol
Appearance
red-orange crystals
Density
1.87 g/cm3
Melting point
51 to 52 °C (124 to 126 °F; 324 to 325 K )
Boiling point
52 °C (126 °F; 325 K ) decomposes
Solubility in water
insoluble
Vapor pressure
0.7 mmHg (20 °C)[1]
Structure
Dipole moment
1.33 D C 2v isomer)D D 3d isomer)
Hazards
Occupational safety and health
Main hazards
Potential carcinogen
GHS labelling
Pictograms
Signal word
Danger
Hazard statements
H251 , H302 , H304 , H315 , H317 , H330 , H351 , H361 , H412
Precautionary statements
P201 , P260 , P273 , P280 , P304+P340+P310 , P403+P233
NFPA 704
Flash point
-23 °C (-9.4 °F)[1]
Lethal dose or concentration (LD, LC):
LD 50 median dose )
15 mg/kg (oral, rat)
NIOSH
PEL (Permissible)
none[1]
REL (Recommended)
TWA 0.1 mg/m3 [1]
IDLH (Immediate danger)
N.D.[1]
Safety data sheet (SDS)
External SDS
Related compounds
Related metal carbonyls
Iron pentacarbonyl Diiron nonacarbonyl Nickel tetracarbonyl
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
Chemical compound
Dicobalt octacarbonyl is an organocobalt compound with composition Co 2 CO )8 metal carbonyl is used as a reagent and catalyst in organometallic chemistry and organic synthesis , and is central to much known organocobalt chemistry .[2] [3] hydroformylation catalysts.[4] molecule consists of two cobalt atoms bound to eight carbon monoxide ligands , although multiple structural isomers are known.[5] labile .
Synthesis, structure, properties [ edit ]
Dicobalt octacarbonyl an orange-colored, pyrophoric solid.[6] carbonylation of cobalt(II ) salts :[6]
2 (CH 3 2 2 2 CO )8 3
The preparation is often carried out in the presence of cyanide , converting the cobalt(II ) salt into a pentacyanocobaltate (II ) complex that reacts with carbon monoxide to yield K[Co(CO )4 . Acidification produces cobalt tetracarbonyl hydride , HCo(CO )4 , which degrades near room temperature to dicobalt octacarbonyl and hydrogen.[3] [7] carbon monoxide gas at about 200 to 300 atm :[3]
2 Co + 8 CO → Co2 CO )8
It exist as a mixture of rapidly interconverting isomers .[2] [3] [5]
The major isomer (on the left in the above equilibrium process) contains two bridging carbonyl ligands linking the cobalt centres and six terminal carbonyl ligands, three on each metal.[5] (CO )3 2 CO )3 and has C2v symmetry . This structure resembles diiron nonacarbonyl (Fe 2 CO )9 terminal and Co–CObridge distances are 1.80 and 1.90 Å, respectively.[8] [9]
The minor isomer has no bridging carbonyl ligands, but instead has a direct bond between the cobalt centres and eight terminal carbonyl ligands, four on each metal atom.[5] (CO )4 CO )4 and has D4d symmetry. It features an unbridged cobalt–cobalt bond that is 2.70 Å in length in the solid structure when crystallized together with C 60 [10]
Isomers of dicobalt octacarbonyl
non-bridged D3d isomer
nonbridged D2d isomer
Reactions [ edit ]
Reduction [ edit ]
Dicobalt octacarbonyl is reductively cleaved by alkali metals and related reagents, such as sodium amalgam . The resulting salts protonate to give tetracarbonyl cobalt hydride :[3]
Co 2 CO )8 CO )4
Na[Co(CO )4 + → H[Co(CO )4 +
Salts of this form are also intermediates in the cyanide synthesis pathway for dicobalt octacarbonyl.[7]
Reactions with electrophiles [ edit ]
Halogens and related reagents cleave the Co–Co bond to give pentacoordinated halotetracarbonyls:
Co 2 CO )8 2 CO )4
Cobalt tricarbonyl nitrosyl is produced by treatment of dicobalt octacarbonyl with nitric oxide:
Co 2 CO )8 CO )3
Reactions with alkynes [ edit ]
The Nicholas reaction is a substitution reaction whereby an alkoxy group located on the α-carbon of an alkyne is replaced by another nucleophile . The alkyne reacts first with dicobalt octacarbonyl, from which is generated a stabilized propargylic cation that reacts with the incoming nucleophile and the product then forms by oxidative demetallation .[11] [12]
The Nicholas reaction
The Pauson–Khand reaction ,[13] alkyne , an alkene, and carbon monoxide cyclize to give a cyclopentenone , can be catalyzed by Co 2 CO )8 [3] [14] [15] [16]
Co 2 CO )8 alkynes to form a stable covalent complex, which is useful as a protective group for the alkyne. This complex itself can also be used in the Pauson–Khand reaction.[13]
Intramolecular Pauson–Khand reactions, where the starting material contains both the alkene and alkyne moieties, are possible. In the asymmetric synthesis of the Lycopodium alkaloid huperzine-Q , Takayama and co-workers used an intramolecular Pauson–Khand reaction to cyclise an enyne containing a tert -butyldiphenylsilyl (TBDPS) protected primary alcohol.[17] conformation .[18]
Dicobalt octacarbonyl can catalyze alkyne trimerisation of diphenylacetylene and its derivatives to hexaphenylbenzenes .[19] [20]
Symmetric diphenylacetylene cyclotrimerization using dicobalt octacarbonyl Asymmetric diphenylacetylene cyclotrimerization using dicobalt octacarbonyl
Hydroformylation [ edit ]
Catalytic cycle for the hydroformylation of a terminal alkene (RCH=CH2 ) to an aldehyde (RCH2 CH 2 ):[4]
1
Carbon monoxide dissociates from cobalt tetracarbonyl hydride to form the active catalyst, HCo(CO )3
2
The cobalt centre π bonds to the alkene
3
The alkene ligand inserts into the cobalt–hydride bond
4
An additional carbonyl ligand coordinates
5
A carbonyl ligand migrates into the cobalt–alkyl bond[21]
6
Dihydrogen adds to the acyl complex
7
The dihidrydo complex eliminates the aldehyde product,[22]
8
An unproductive and reversible side reaction
Hydrogenation of Co 2 CO )8 cobalt tetracarbonyl hydride H[Co(CO )4 :[23]
Co 2 CO )8 2 CO )4
This hydride is a catalyst for hydroformylation – the conversion of alkenes to aldehydes .[4] [23] catalytic cycle for this hydroformylation is shown in the diagram.[4] [21] [22]
Substitution reactions [ edit ]
The CO ligands can be replaced with tertiary phosphine ligands to give Co 2 CO )− 8 x PR 3 x [3] Hard " Lewis bases, e.g. pyridine , cause disproportionation :
12 C5 H 5 2 CO )8 C 5 H 5 N )6 CO )4 2
Methylidynetricobaltnonacarbonyl , HCCo3 CO )9 organocobalt cluster compound structurally related to tetracobalt dodecacarbonyl
Conversion to higher carbonyls [ edit ]
Heating causes decarbonylation and formation of tetracobalt dodecacarbonyl :[3] [24]
2 Co2 CO )8 4 CO )12
Like many metal carbonyls, dicobalt octacarbonyl abstracts halides from alkyl halides. Upon reaction with bromoform , it converts to methylidynetricobaltnonacarbonyl , HCCo3 CO )9 , by a reaction that can be idealised as:[25]
9 Co2 CO )8 3 3 CO )9 2
Co 2 CO )8 pyrophoric and releases carbon monoxide upon decomposition.[26] National Institute for Occupational Safety and Health has recommended that workers should not be exposed to concentrations greater than 0.1 mg/m3 [27]
References [ edit ]
^ a b Pauson, Peter L. ; Stambuli, James P.; Chou, Teh-Chang; Hong, Bor-Cherng (2014). "Octacarbonyldicobalt". Encyclopedia of Reagents for Organic Synthesis John Wiley & Sons . pp. 1–26. doi :10.1002/047084289X.ro001.pub3 . ISBN 9780470842898
^ a b c d e f g h Donaldson, John Dallas; Beyersmann, Detmar (2005). "Cobalt and Cobalt Compounds". Ullmann's Encyclopedia of Industrial Chemistry doi :10.1002/14356007.a07_281.pub2 . ISBN 3527306730
^ a b c d Elschenbroich, C.; Salzer, A. (1992). Organometallics: A Concise Introduction (2nd ed.). Weinheim: Wiley-VCH . ISBN 3-527-28165-7
^ a b c d Sweany, Ray L.; Brown, Theodore L. (1977). "Infrared spectra of matrix-isolated dicobalt octacarbonyl. Evidence for the third isomer". Inorganic Chemistry 16 2 ): 415–421. doi :10.1021/ic50168a037 .
^ a b Gilmont, Paul; Blanchard, Arthur A. (1946). Dicobalt Octacarbonyl, Cobalt Nitrosyl Tricarbonyl, and Cobalt Tetracarbonyl Hydride . Inorganic Syntheses. Vol. 2. pp. 238–243. doi :10.1002/9780470132333.ch76 . ISBN 9780470132333
^ a b Orchin, Milton (1953). "Hydrogenation of Organic Compounds with Synthesis Gas" . Advances in Catalysis . Vol. 5. Academic Press . pp. 385–415. ISBN 9780080565095
^ Sumner, G. Gardner; Klug, Harold P.; Alexander, Leroy E. (1964). "The crystal structure of dicobalt octacarbonyl" . Acta Crystallographica 17 6 ): 732–742. doi :10.1107/S0365110X64001803
^ Green, Jennifer C.; Green, Malcolm L. H. ; Parkin, Gerard (2012). "The occurrence and representation of three-centre two-electron bonds in covalent inorganic compounds". Chemical Communications 2012 (94 ): 11481–11503. doi :10.1039/c2cc35304k . PMID 23047247 .
^ Garcia, Thelma Y.; Fettinger, James C.; Olmstead, Marilyn M.; Balch, Alan L. (2009). "Splendid symmetry: Crystallization of an unbridged isomer of Co2 CO )8 2 CO )8 · C 60 Chemical Communications 2009 (46 ): 7143–7145. doi :10.1039/b915083h . PMID 19921010 .
^ Nicholas, Kenneth M. (1987). "Chemistry and synthetic utility of cobalt-complexed propargyl cations". Acc. Chem. Res. 20 6 ): 207–214. doi :10.1021/ar00138a001 .
^ Teobald, Barry J. (2002). "The Nicholas reaction: The use of dicobalt hexacarbonyl-stabilised propargylic cations in synthesis". Tetrahedron 58 21 ): 4133–4170. doi :10.1016/S0040-4020(02 )00315-0 .
^ a b Pauson, P. L. ; Khand, I. U. (1977). "Uses of Cobalt-Carbonyl Acetylene Complexes in Organic Synthesis". Ann. N. Y. Acad. Sci. 295 (1 ): 2–14. Bibcode :1977NYASA.295....2P . doi :10.1111/j.1749-6632.1977.tb41819.x . S2CID 84203764 .
^ Blanco-Urgoiti, Jaime; Añorbe, Loreto; Pérez-Serrano, Leticia; Domínguez, Gema; Pérez-Castells, Javier (2004). "The Pauson–Khand reaction, a powerful synthetic tool for the synthesis of complex molecules". Chem. Soc. Rev. 33 1 ): 32–42. doi :10.1039/b300976a . PMID 14737507 .
^ Schore, Neil E. (1991). "The Pauson–Khand Cycloaddition Reaction for Synthesis of Cyclopentenones". Org. React. 40 doi :10.1002/0471264180.or040.01 . ISBN 0471264180
^ Gibson, Susan E.; Stevenazzi, Andrea (2003). "The Pauson–Khand Reaction: The Catalytic Age Is Here!". Angew. Chem. Int. Ed. 42 16 ): 1800–1810. doi :10.1002/anie.200200547 . PMID 12722067 .
^ Nakayama, Atsushi; Kogure, Noriyuki; Kitajima, Mariko; Takayama, Hiromitsu (2011). "Asymmetric Total Synthesis of a Pentacyclic Lycopodium Alkaloid: Huperzine-Q". Angew. Chem. Int. Ed. 50 35 ): 8025–8028. doi :10.1002/anie.201103550 . PMID 21751323 .
^ Ho, Tse-Lok (2016). "Dicobalt Octacarbonyl" . Fiesers' Reagents for Organic Synthesis . Vol. 28. John Wiley & Sons . pp. 251–252. ISBN 9781118942819
^ Vij, V.; Bhalla, V.; Kumar, M. (8 August 2016). "Hexaarylbenzene: Evolution of Properties and Applications of Multitalented Scaffold". Chemical Reviews 116 (16 ): 9565–9627. doi :10.1021/acs.chemrev.6b00144 .
^ Xiao, W.; Feng, X.; Ruffieux, P.; Gröning, O.; Müllen, K.; Fasel, R. (18 June 2008). "Self-Assembly of Chiral Molecular Honeycomb Networks on Au(111)". Journal of the American Chemical Society 130 (28 ): 8910–8912. doi :10.1021/ja7106542 .
^ a b Heck, Richard F. ; Breslow, David S. (1961). "The Reaction of Cobalt Hydrotetracarbonyl with Olefins". Journal of the American Chemical Society 83 19 ): 4023–4027. doi :10.1021/ja01480a017 .
^ a b Halpern, Jack (2001). "Organometallic chemistry at the threshold of a new millennium. Retrospect and prospect" . Pure and Applied Chemistry 73 2 ): 209–220. doi :10.1351/pac200173020209
^ a b Pfeffer, M.; Grellier, M. (2007). "Cobalt Organometallics". Comprehensive Organometallic Chemistry III . Vol. 7. Elsevier . pp. 1–119. doi :10.1016/B0-08-045047-4/00096-0 . ISBN 9780080450476
^ Chini, P. (1968). "The closed metal carbonyl clusters". Inorganica Chimica Acta Reviews 2 doi :10.1016/0073-8085(68 )80013-0 .
^ Nestle, Mara O.; Hallgren, John E.; Seyferth, Dietmar; Dawson, Peter; Robinson, Brian H. (2007). "μ3 3 Inorg. Synth. 20 doi :10.1002/9780470132517.ch53 . ISBN 9780470132517
^ Cole Parmer MSDS
^ CDC - NIOSH Pocket Guide to Chemical Hazards
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