Related Experiment Video
Updated: Aug 7, 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
N4 ring as a square planar ligand in novel MN4 species
1School of Chemical Engineering, Shanghai Institute of Technology, Shanghai 200235, People's Republic of China. chengliping@sit.edu.cn
Abstract:
Ab initio (MP2) and density functional theory (DFT) methods are used to examine a series of MN4 compounds, where M is an alkaline-earth cation (Mg2+, Ca2+, Sr2+, Ba2+), and N4(2-) is a six--electron ring. All pyramidal structures except MgN4 are the most energetically favored for all singlet MN4 systems considered here. For MgN4, the CS structure with dicoordinated Mg out of the N4 ring plane is the most stable of all. Among these systems, the pyramidal CaN4, SrN4, BaN4 and the planar C(S) structure containing dicoordinated Ba are stable as singlet molecules due to their significant isomerization or dissociation barriers (21.3-94.1 kcal/mol). Structural, natural bond orbital (NBO), and molecular orbital (MO) analyses indicate that the bonding in the BaN4 system has a larger covalent character as compared with other MN4 systems. In addition, substantial d character is found in the bonding of the MN4 (M = Ca2+, Sr2+, Ba2+) species.
More Related Videos
Related Concept Videos
Coordination Number and Geometry
Valence Bond Theory
Crystal 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,...
Coordination Compounds and Nomenclature
Metal-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...
Crystal 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...

