Analysis of NMR shifts of high-spin cobalt(II) pyrazolylborate complexes

We present a detailed study on the correlation of the nuclear magnetic resonance (NMR) parameters with the results of density functional theory (DFT) calculations performed for paramagnetic high-spin cobalt(II) complexes with trispyrazolylborate ligands. This work is a first attempt to calculate dipolar and contact shifts in high-spin cobalt(II) pyrazolylborate systems. The calculation results show frontier orbitals that may be responsible for the contact shift. The contact shift values are compared with the dipolar shift ones. The latter shift values were both obtained from experimental data and calculated using DFT methods. We attempt to explain the dipolar effect, which may have a great share in NMR chemical shift of paramagnetic compounds.