The nature of the metal–nitric oxide bond in the [M(CN)5(NO)]q (M=Cr, Mn, Fe, Ru, Os, and Co) and trans-[Ru(NH3)4L(NO)]q (L=pyrazine, pyridine, N2, H2O, Cl−, CN−, NO2-) complexes: A bond-energy decomposition analysis

A bond-energy decomposition analysis (EDA) has been carried out to investigate the nature of the MNO bonding in the pentacyanonitrosyl [Cr(CN)5(NO)]4−, [Mn(CN)5(NO)]3−, [M(CN)5(NO)]2− (M=Fe, Ru, Os), [Co(CN)5(NO)]3− complexes and in the trans-nitrosyltetraammineruthenium [Ru(NH3)4L(NO)]q (L=pyrazine, pyridine, N2, H2O (q=3); and L=Cl−, CN−, NO2- (q=2)) complexes. For the pentacyanonitrosyl complexes of Fe, Ru, and Os three fragmentation models have been considered: {M(CN)5}3−⋯{NO}+, {M(CN)5}2−⋯{NO}0, and {M(CN)5}−⋯{NO}−. The results of the EDA show that the linear MNO bonds are predominantly covalent with a significant (∼70%) contribution of π orbital interaction between unpaired electrons on the dπ and π∗(NO0) orbitals. EDA results point to the correlation between MNO and ML binding interactions in the trans-[Ru(NH3)4L(NO)]q complexes.