Low spin-high spin planar Ni(II) complexes with phosphinic amidato ligands

The bis(di-tert-butylphosphinic-N-tert-pentyl-amidato-N, O) Ni(II) complex is planar and has a spin triplet of low energy (300–400 cm−1) close to the singlet ground state. The measured absorption spectrum exhibits two ligand field bands in the near-infrared and some other features in the visible which in part are strongly temperature dependent. The fit of angular overlap model parameters to experiment supplies parameter values which are comparable to those derived for similar ligands with equal donor atoms. As is usual for a planar configuration, the model is extended by including s-orbital mixing into the dσ-orbital set inferred from each ligand separately. The appropriate choice of esd(N) and esd(O) energy parameters resulting from this intermixing is important for reproducing the spectra and the measured paramagnetism which also strongly changes with temperature.