Density functional B3LYP/6-311+G(3df,2p)//B3LYP/6-31G** calculations show that strong η 1 - and η 2 -coordinated complexes, HScOH-N 2 ( 2 A ' ) and N 2 Sc(H)OH ( 2 A''), bound 28.1 and 31.0 kcal/mol, respectively, can be formed in the ScO/N 2 /H 2 system. The calculations reveal interesting interplay between the H 2 and N 2 ligands, as an addition of H 2 increases the reactivity of ScO with respect to N 2 and vice versa. ScO is demonstrated to enhance the reaction of nitrogen hydrogenation through the ScO ( 2 Σ + )+N 2 +H 2 ->TS2->N 2 ScO ( 2 A'')+H 2 ->N 2 ScO-H 2 ( 2 A'')->TS3->N 2 Sc(H)OH ( 2 A'')->TS5->NN(H)ScOH TS6->N 2 H 2 ScO ( 2 A ' ) mechanism.