Cyclopentadienylcobalt dicarbonyl

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Cyclopentadienyl cobalt dicarbonyl
Identifiers
3D model (
JSmol
)
ChemSpider
ECHA InfoCard
 100.031.933 Edit this at Wikidata
EC Number
  • 235-139-8
  • InChI=1S/C5H5.2CO.Co/c1-2-4-5-3-1;2*1-2;/h1-5H;;;/q-1;;; ☒N
    Key: AEVRNKXPLOTCBW-UHFFFAOYSA-N ☒N
  • InChI=1/C5H5.2CO.Co/c1-2-4-5-3-1;2*1-2;/h1-5H;;;/q-1;;;
    Key: AEVRNKXPLOTCBW-UHFFFAOYAD
SMILES
  • [cH-]1cccc1.[O+]#C[Co-](C#[O+])
Properties
CpCo(CO)2
Molar mass 180.05 g/mol
Appearance Dark red to black liquid
Density 1.35 g/cm3
Melting point −22 °C (−8 °F; 251 K)
Boiling point 139 to 140 °C (282 to 284 °F; 412 to 413 K) (710 mmHg)
37-38.5 °C (2 mmHg)
Insoluble
Hazards
GHS labelling:
GHS02: FlammableGHS06: ToxicGHS08: Health hazard
Danger
H226, H301, H311, H331, H334, H341, H351, H412
Flash point 26.7 °C (80.1 °F; 299.8 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Cyclopentadienylcobalt dicarbonyl is an

sandwich complex. It is a dark red air sensitive liquid. This compound features one cyclopentadienyl ring that is bound in an η5-manner and two carbonyl ligands. The compound is soluble in common organic solvents.[1]

Preparation

CpCo(CO)2 was first reported in 1954 by Piper,

cobalt carbonyl with cyclopentadiene.[2]
It is prepared commercially by the same method:

Co2(CO)8 + 2 C5H6 → 2 C5H5Co(CO)2 + H2 + 4 CO

Alternatively, it is generated by the high pressure carbonylation of bis(cyclopentadienyl)cobalt (cobaltocene) at elevated temperature and pressures:[1]

Co(C5H5)2 + 2 CO → C5H5Co(CO)2 + "C5H5"

The compound is identified by strong bands in its

IR spectrum at 2030 and 1960 cm−1.[3]

Reactions

CpCo(CO)2 catalyzes the cyclotrimerization of alkynes.[4][5] The catalytic cycle begins with dissociation of one CO ligand forming bis(alkyne) intermediate.[6]

CpCo(CO)2 + 2 R2C2 → CpCo(R2C2)2 + 2 CO

This reaction proceeds by formation of

metal-alkyne complexes by dissociation of CO. Although monoalkyne complexes CpCo(CO)(R1C2R2) have not been isolated, their analogues, CpCo(PPh3)(R1C2R2) are made by the following reactions:[6]

CpCo(CO)2 + PR3 → CO + CpCo(CO)(PR3)
CpCoL(PR3) + R2C2 → L + CpCo(PR3)(R2C2) (where L = CO or PR3)

CpCo(CO)2 catalyzes the formation of pyridines from a mixture of alkynes and nitriles. Reduction of CpCo(CO)2 with sodium yields the dinuclear radical [Cp2Co2(CO)2]−, which reacts with alkyl halides to give the dialkyl complexes [Cp2Co2(CO)2R2]. Ketones are produced by carbonylation of these dialkyl complexes, regenerating CpCo(CO)2.[6]

The

pentamethylcyclopentadienyl
analogue Cp*Co(CO)2 (CAS RN#12129-77-0) is well studied. The Rh and Ir analogues, CpRh(CO)2 (CAS RN#12192-97-1) and CpIr(CO)2 (CAS RN#12192-96-0), are also well known.

References

  1. ^
    doi:10.1002/9780470132388.ch31
    .
  2. doi:10.1016/0022-1902(55)80053-X
    .
  3. ^ "Cobalt, dicarbonyl(η5-2,4-cyclopentadien-1-yl)-".
  4. doi:10.1002/ange.19840960804
    .
  5. doi:10.1002/ejic.200500394
    .
  6. ^
    doi:10.1002/047084289X.rd078
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