Looking at the contributions given in Table 4 and Table S6 in the ESI, it can be noted that in complex 1 the contribution to the bond order coming from σ-NLMOs ranges from 70-91% denoting a high predominance of the σ-character of the bond. On the other hand, for complex 2 a similar predominance for Bk–OCO3 bonds is observed (74-87%) but significantly deviates for Bk–OH bonds (56%). This means that the bond order in the latter bonds is increased by π contributions.