Related Experiment Video
Updated: Jul 14, 2026
06:31
Preparation of SNS Cobalt(II) Pincer Model Complexes of Liver Alcohol Dehydrogenase
Published on: March 19, 2020
A study of (binap)(enyne)tetracarbonyldicobalt(0) complexes
Susan E Gibson1, David J Hardick, Peter R Haycock
1Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AY, UK. s.gibson@imperial.ac.uk
Chemistry (Weinheim an Der Bergstrasse, Germany)
|June 28, 2007
Summary
Four dicobalt(0) complexes containing binaphthyl and enyne ligands were synthesized. Their reactivity was monitored, revealing the formation of a cobalt(-1) hydride species at moderate temperatures, confirmed by X-ray crystallography and NMR.
Area of Science:
- Organometallic Chemistry
- Cobalt Complexes
- Catalysis
Background:
- Cobalt complexes are crucial in organic synthesis, particularly in reactions like the Pauson-Khand reaction.
- Understanding the reactivity of tetracarbonyldicobalt(0) complexes with chiral ligands is key to developing new catalytic systems.
Purpose of the Study:
- To synthesize and characterize novel (binap)(enyne)tetracarbonyldicobalt(0) complexes.
- To investigate the reactivity and thermal stability of these complexes using variable temperature NMR spectroscopy.
- To elucidate the structure of key reaction intermediates and confirm their presence under reaction conditions.
Main Methods:
- Synthesis of four distinct (binap)(enyne)tetracarbonyldicobalt(0) complexes.
- Variable temperature 31P NMR spectroscopy to monitor reaction progress and intermediate formation.
- X-ray crystallography for structural determination of the cobalt(-1) hydride species.
- NMR spectroscopy to verify the presence of the intermediate under Pauson-Khand reaction conditions.
Main Results:
- Successful synthesis of four (binap)(enyne)tetracarbonyldicobalt(0) complexes.
- Formation of a (binap)dicarbonylhydridocobalt(-1) species (12) observed between 35-55°C.
- Temperature-dependent formation of 12, influenced by the enyne substrate.
- Structural confirmation of complex 12 via X-ray crystallography.
- Verification of 12's presence during Pauson-Khand reaction conditions.
Conclusions:
- The synthesized dicobalt(0) complexes exhibit reactivity leading to the formation of a cobalt(-1) hydride intermediate.
- The formation temperature of this intermediate is substrate-dependent, offering insights into reaction control.
- The structural characterization and verification under reaction conditions provide a foundation for understanding cobalt-mediated alkyne-alkene coupling reactions.
More Related Videos
Related Concept Videos
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
02:51Metal-Ligand Bonds
The hemoglobin in the blood, the chlorophyll in green plants, vitamin B-12, and the catalyst used in the manufacture of polyethylene all contain coordination compounds. Ions of the metals, especially the transition metals, are likely to form complexes.
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
02:57Coordination Number and Geometry
For transition metal complexes, the coordination number determines the geometry around the central metal ion. Table 1 compares coordination numbers to molecular geometry. The most common structures of the complexes in coordination compounds are octahedral, tetrahedral, and square planar.
02:54Coordination Compounds and Nomenclature
In most main group element compounds, the valence electrons of the isolated atoms combine to form chemical bonds that satisfy the octet rule. For instance, the four valence electrons of carbon overlap with electrons from four hydrogen atoms to form CH4. The one valence electron leaves sodium and adds to the seven valence electrons of chlorine to form the ionic formula unit NaCl (Figure 1a). Transition metals do not normally bond in this fashion. They primarily form coordinate covalent bonds, a...