Related Experiment Video
Updated: May 17, 2026
Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of Chalcogenidoplumbates(II or IV)
Published on: December 29, 2016
(2.2.2-Cryptand)potassium tetra-kis-(η(2)-ethyl-ene)cobaltate(-I)
William W Brennessel1, John E Ellis
1Department of Chemistry, 207 Pleasant Street SE, University of Minnesota, Minneapolis, MN 55455, USA.
Abstract:
The title salt, [K(C(18)H(36)N(2)O(6))][Co(C(2)H(4))(4)], is one of only two known homoleptic ethyl-enemetalates. The cation and anion are well separated, which gives an unperturbed tetra-hedral anion as is expected for a formally Co(-I)d(10) metal center. The considerable elongation of the C=C bonds of the ethyl-ene ligands [average 1.401 (6) Å], relative to that of free ethyl-ene (1.333 Å), is consistent with metal→π* back-bonding models. One arm of the 2.2.2-cryptand (4,7,13,16,21,24-hexa-oxa-1,10-diaza-bicyclo-[8.8.8]hexa-cosa-ne) complexant is disordered and was modeled over two positions with a refined occupancy ratio of 0.559 (2):0.441 (2). In the crystal, the cationic K(2.2.2-cryptand) units are linked via C-H⋯O hydrogen bonds, forming inversion dimers. There are no other significant inter-molecular inter-actions in the crystal structure.
Related Concept Videos
02:36Crown Ethers
03:02Colors and Magnetism
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.
02:42Valence Bond Theory
02:34Structural Isomerism
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
02:46Crystal Field Theory - Tetrahedral and Square Planar 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,...