After extensive trials, we discovered that excluding the D3 correction from the calculation resolved the problem, resulting in the structure optimizing to H2-NiKur- , where no ill-behaved frequencies were detected (Figure , top). Additionally, in the correct H2-NiKur-(1) structure, the H2 molecule is closer to the binding atom by approximately 0.1 Å, while the H-H bond is longer by approximately 0.03 Å. This indicates more significant activation of the dihydrogen bond and, thus, a stronger interaction between Ni I and H2.