Related Experiment Video
Updated: Sep 6, 2026
Preparation of SNS Cobalt(II) Pincer Model Complexes of Liver Alcohol Dehydrogenase
Published on: March 19, 2020
Hexa- and hepta-coordinate cobalt(II) complexes bearing bis(2-pyridylmethyl)ether
Ryo Toriba1, Takuya Miyazaki1, Tomoyo Misawa-Suzuki1
1Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554, Japan. t_misawa@sophia.ac.jp.
Abstract:
Hexa- and hepta-coordinate cobalt(II) complexes bearing bis(2-pyridylmethyl)ether (bpme) as a tridentate supporting ligand were synthesized and structurally characterized by single crystal X-ray diffraction (SCXRD). The reactions of the penta-coordinate dichloridocobalt(II) complex, [CoIICl2(bpme)], with a molar equivalent of AgX (X = NO3 and CH3CO2) afforded hexa-coordinate octahedral complexes, fac-[CoIICl(L)(bpme)] (L = nitrato-κ2O1,O2; [1] and acetato-κ2O1,O2; [2]), whereas those with two molar equivalents of AgNO3 resulted in the isolation of the hepta-coordinate pentagonal bipyramidal complex, [CoII(nitrato-κ2O1,O2)2(bpme)] ([3]). When 2,2'-bipyridine (bpy) was reacted with [CoIICl2(bpme)], one bpy-coordinated octahedral complex, mer-[CoIICl(bpy)(bpme)]+ ([4]+), was formed. Furthermore, it has been suggested that the reactions with a molar equivalent of AgClO4 in acetonitrile could afford octahedral complexes with meridional geometry, concomitant with [CoIICl2(bpme)] and mer-[CoII(bpme)2]2+: a perchlorato-coordinated monomer, mer-[CoII(NCCH3)(OH2)(OClO3)(bpme)]ClO4 ([5]ClO4), and a doubly chlorido-bridged dimer, mer-[{CoII(NCCH3)(bpme)}2(μ-Cl)2](ClO4)2 ([6](ClO4)2), both of which were identified only by SCXRD analysis. The electronic structures of the mononuclear complexes [1]-[3], all having the Co(II) centre (S = 3/2) at 296-298 K, are discussed comprehensively with respect to electrochemical, spectroscopic, and theoretical investigations.
Related Concept Videos
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...
02:51Metal-Ligand Bonds
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...
02:52Stereoisomerism
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
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.
02:57Coordination Number and Geometry
01:19Complexation Equilibria: The Chelate Effect