Structure−Function−Performance Relationship of Bis(cyclopentadienyl)-Based Group 4 Metallocenes: A DFT Study

In this work a DFT study of the structure−function−performance relationship of bis(cyclopentadienyl)-based (Cp 2 -based) group 4 metallocenes is presented. In particular, the effects of (1) the metal, (2) the ansa -bridge, and (3) the π-ligand on steric and electronic parameters, as well as on energetic values, were investigated. In addition, the transition states of the activation reaction of the metallocenes with an alkyllithium compound (i.e., MeLi) were computed. The calculated ΔΔ G values confirm that the accessibility of the reaction center and, thus, the reactivity of the metallocenes are generally improved by increasing the Cp′−M and M−Cl distances and by decreasing Cp′−M−Cp′ angles (M = Ti, Zr, Hf; Cp′ = centroid of the five-membered ring for any Cp-based ligand). Furthermore, the activation process is enhanced when the metallocenes show small gaps between the HOMO of MeLi and the LUMO of the metallocene, as well as high NPA charges on the metal. Additionally, the presented results show that the introduction of an ansa -bridge and withdrawing substituents on the Cp ring enhance the activation process of the metallocenes with MeLi. Thus, structural and electronic parameters may serve as guidance for the design of new high-performance metallocenes for hydrogenation and hydrosilylation reactions.