Linear MgCp∗2 vs Bent CaCp∗2: London Dispersion, Ligand-Induced Charge Localizations, and Pseudo-Pregostic C-H⋯Ca Interactions

Rumpa Pal, Stefan Mebs, Ming W. Shi, Dylan Jayatilaka, Joanna M. Krzeszczakowska, Lorraine A. Malaspina, Michal Wiecko, Peter Luger, Malte Hesse, Yu Sheng Chen, Jens Beckmann, Simon Grabowsky

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


In the family of metallocenes, MgCp∗2 (Cp∗ = pentamethylcyclopentadienyl) exhibits a regular linear sandwich structure, whereas CaCp∗2 is bent in both the gas phase and solid state. Bending is typically observed for metal ions which possess a lone pair. Here, we investigate which electronic differences cause the bending in complexes lacking lone pairs at the metal atoms. The bent gas-phase geometry of CaCp∗2 suggests that the bending must have an intramolecular origin. Geometry optimizations with and without dispersion effects/d-type polarization functions on MCp2 and MCp∗2 gas-phase complexes (M = Ca, Mg) establish that attractive methyl⋯methyl London dispersion interactions play a decisive role in the bending in CaCp∗2. A sufficient polarizability of the metal to produce a shallow bending potential energy curve is a prerequisite but is not the reason for the bending. Concomitant ligand-induced charge concentrations and localizations at the metal atoms are studied in further detail, for which real-space bonding and orbital-based descriptors are used. Low-temperature crystal structures of MgCp∗2 and CaCp∗2 were determined which facilitated the identification and characterization of intermolecular pseudo-pregostic interactions, C-H⋯Ca, in the CaCp∗2 crystal structure.

Original languageEnglish
Pages (from-to)4906-4920
Number of pages15
JournalInorganic Chemistry
Issue number9
Publication statusPublished - 7 May 2018


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