Related Experiment Video
Updated: Jun 23, 2026
Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents
Published on: May 28, 2014
Novel bispidine ligands and their first-row transition metal complexes: trigonal bipyramidal and trigonal prismatic
Peter Comba1, Christina Haaf, Hubert Wadepohl
1Universität Heidelberg, Anorganisch-Chemisches Institut, INF 270, D-69120 Heidelberg, Germany. peter.comba@aci.uni-heidelberg.de
Abstract:
Four very rigid second generation bispidine-based ligands (bispidine = 3,7-diazabicyclo[3.3.1]nonane; tetra-, penta- and hexadentate; exclusively tertiary amine donors except for one of the pentadentate ligands, where one of the donors is a pyridyl group) and their Co(II), Ni(II), Cu(II), and Zn(II) complexes are reported. The experimentally determined X-ray crystal structures and computational data, based on empirical force field (MM) and approximate density functional theory (DFT) calculations, indicate that these new ligands, which are based on a modular system and therefore allow for a wide range of donor sets and coordination geometries, have rather large cavities (i.e., lead to a preference for +II over +III oxidation states and induce relatively low ligand fields), enforce trigonal geometries (pentacoordinate systems: preference for trigonal bipyramidal, hexacoordinate complexes: preference for trigonal prismatic), and lead, especially for Cu(II), to very high complex stabilities.
Related Concept Videos
02:57Coordination Number and Geometry
02:42Valence Bond Theory
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...
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,...
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...