In the K2[M(CN)4]·xH2O (M = Ni, Pd, Pt) series, the CN ligand is found to donate electron density to the K ion, which is detected as a decrease in the K 2p BE. The charge donated is proportional to that removed from the inner metal (M) via π-back bonding.
19 November 2019 in European Journal of Inorganic Chemistry
The charge density accumulated at the CN 5σ orbital, via π-back bonding interaction, determines the crystal field splitting for the Fe(ii) atom and the temperature where the spin transition is observed.