| Abstract
| - Various structures of complexes of the cluster Ni3 with 3 to 12 N2 ligands were modeled with a gradient-corrected density functional method. The stability of different types of bonding was considered and the moststable structures of Ni3(N2)x complexes (x = 3−9, 12) were determined for neutral, cationic, and anionicsystems. For the most stable structure of the neutral complex with three and six N2 ligands, we calculatedaverage ligand binding energies of 116 and 98 kJ/mol, respectively; the binding energy per ligand decreaseswith increasing number of ligand molecules. For canonical ensembles of mono- and trinuclear complexeswith N2 ligands at varying molar ratio k = [N2]:[Ni3], our results suggest that, in agreement with experiment,the complex Ni3(N2)6 is among the dominating species at saturation; yet, at sufficiently large molar ratios k,the trinuclear complex with seven ligands, not observed in experiment, also plays an important role in thesimulated distributions. It is unclear whether this partial discrepancy in the product distribution originatesfrom complications to simulate the experimental situation or from some aspects of the experimental procedure.Coordination of more than seven N2 ligands is predicted to lead to a partial or full destruction of the Ni3moieties into mononuclear N2 ligated complexes. The type of bonding of the N2 ligands (end-on, side-on,hapticity) was found to affect the characteristics of the complexes, e.g. the binding energy, the charge of theNi3 moiety, and the activation of the ligands. End-on coordination of N2 molecules to a Ni atom of the Ni3unit entails the most stable type of bonding, whereas side-on coordination causes a stronger elongation ofN−N bonds. The ionization potential and the electron affinity of a Ni3 cluster were calculated to increaseafter association of ligands.
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