Knowledge Bank

In order to determine experimentally the character of metal-ligand bonds in $tris-2,21-dipyridyl-complexes$ of transition metals in low oxidation states the electron paramagnetic resonance of the ions $[Cr1dip3]+,[V0dip3]$ and $[Ti-1dip3]$- was studied. The positions of the lines in the EPR spectra are given by the spin hamiltonian $H=g\beta S\cdot H+aS\cdot I+\Sigma NaNS\cdot IN$, where the last term describes the interaction with the nitrogen nuclei of the ligands. Isotropic hyperfine constants and g factors are given. The HFS is mainly accounted for by the exchange polarization of inner core s electrons. Contributions of 4s electrons to the HFS are discussed. The numerical results obtained indicate strong $\sigma -bonding$ between metal 4s and ligand $\Sigma 0+$ orbitals which increases in the order $Ti-,V0,Cr+$.