Vibrational blue shift of coordinated N2 in [Fe3O(OAc)6(N2)n]+: "non-classical" dinitrogen complexes

We present "non-classical" dinitrogen Fe(iii) oxo acetate complexes in vacuo utilizing Infrared Photodissociation (IR-PD) at cryo temperatures. The IR-PD spectra reveal a blue shift of the N2 stretching vibration frequencies in the complexes. Density Functional Theory (DFT) calculations confirm the experiments and indicate strengthened N-N bonds due to pronounced σ bonding and a lack of π back donation.