Stacking of cyclopentadienyl organometallic sandwich and half-sandwich compounds. Strong interactions of sandwiches at large offsets

Abstract

73% of stacking of Cp sandwiches in the CSD is at large offsets, since these interactions are relatively strong. Much weaker stacking between Cp half-sandwiches is surprising 60% of all stacks, due to more simultaneous interactions.

New Type of Aromatic π‐Systems for Anion Recognition: Strong Anion‐π and C−H⋅⋅⋅Anion Interactions Between Halides and Aromatic Ligands in Half‐Sandwich Compounds

“…We show that these ligands can form some of the strongest anion-π interactions with halides, since the electrostatic potential surfaces above their ring centres can be positive. [36,51,52] Moreover, aromatic ligands in half-sandwich compounds are capable of forming even stronger CÀ H•••X À hydrogen bonds with halide anions, as well as σ-complexes, since electrostatic potentials at hydrogen atoms of aromatic rings are even more positive.…”

Influence of Solvent in Crystal Engineering: A Significant Change to the Order–Disorder Transition in Ferrocene

“…Understanding these weak interactions has particular importance in the pharmaceutical sector, where a variety of fluorinated active pharmaceutical ingredients have been developed . This study is of special interest to the crystal engineering − and structure simulation − communities, as it highlights and scrutinizes some of the fundamental weak interactions that hold molecules together in solid materials.…”

Stacking Interactions between Indenyl Ligands of Transition Metal Complexes: Crystallographic and Density Functional Study

“…The increased dispersion interactions due to transition metal coordination make the ferrocene dimer (−3.37 kcal/mol) more stable than the benzene dimer (−2.76 kcal/mol). 28 If the other ligands of the Cp complex are electron-withdrawing (as CO and CN − ), the electrostatic potential surface above the Cp ring in a half-sandwich compound becomes positive, causing very strong stacking interaction between the Cp half-sandwich and benzene (−4.46 kcal/mol) and significantly weaker stacking between two Cp half-sandwich compounds (−2.87 kcal/mol). 28 Stacking with large offsets also depends on both transition metal coordination and the electrostatic potential surface of the Cp ligand.…”

“…28 If the other ligands of the Cp complex are electron-withdrawing (as CO and CN − ), the electrostatic potential surface above the Cp ring in a half-sandwich compound becomes positive, causing very strong stacking interaction between the Cp half-sandwich and benzene (−4.46 kcal/mol) and significantly weaker stacking between two Cp half-sandwich compounds (−2.87 kcal/mol). 28 Stacking with large offsets also depends on both transition metal coordination and the electrostatic potential surface of the Cp ligand. It was shown that stacking at large offset is relatively strong if the overlapping edges of molecules have a gradient of electrostatic potential, so that the opposite ends of the potentials overlay.…”

“…18,19 These interactions are particularly important in the field of medicinal chemistry; [20][21][22][23] metal-arene complexes (in particular of ruthenium) are known to exhibit anticancer activity by disrupting the structure of DNA through stacking interactions. 19,[24][25][26] The works of our group later showed that stacking interactions between two coordinated benzenes and between two coordinated Cp anions 28 are also stronger than stacking between uncoordinated benzenes.…”