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Chemical compound From Wikipedia, the free encyclopedia
Cyclopentadienylcobalt dicarbonyl is an organocobalt compound with formula (C5H5)Co(CO)2, abbreviated CpCo(CO)2. It is an example of a half-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]
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ChemSpider | |
ECHA InfoCard | 100.031.933 |
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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 | |
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GHS labelling: | |
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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CpCo(CO)2 was first reported in 1954 by Piper, Cotton, and Wilkinson who produced it by the reaction of cobalt carbonyl with cyclopentadiene.[2] It is prepared commercially by the same method:
Alternatively, it is generated by the high pressure carbonylation of bis(cyclopentadienyl)cobalt (cobaltocene) at elevated temperature and pressures:[1]
The compound is identified by strong bands in its IR spectrum at 2030 and 1960 cm−1.[3]
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]
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 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.
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