Revisiting the origin of the bending in group 2 metallocenes AeCp (Ae = Be-Ba).

Metallocenes are well-established compounds in organometallic chemistry, and can exhibit either a coplanar structure or a bent structure according to the nature of the metal center (E) and the cyclopentadienyl ligands (Cp). Herein, we re-examine the chemical bonding to underline the origins of the geometry and stability observed experimentally. To this end, we have analysed a series of group 2 metallocenes [Ae(CR)] (Ae = Be-Ba and R = H, Me, F, Cl, Br, and I) with a combination of computational methods, namely energy decomposition analysis (EDA), polarizability model (PM), and dispersion interaction densities (DIDs).

Understanding Trends in Molecular Bond Angles.

Trends in bond angle are identified in a systematic study of more than a thousand symmetric triatomic molecules. We show that, in series where atoms and are each varied within a group, the following trends hold: (1) the bond angle decreases for more polarizable central atoms , and (2) the angle increases for more polarizable outer atoms . The physical underpinning is provided by the extended Debye polarizability model for the chemical bond angle, hence our present findings also serve as validation of this simple classical model.

Periodic Hartree-Fock and hybrid density functional calculations on the metallic and the insulating phase of (EDO-TTF)2PF6.

The insulating and conducting phases of (EDO-TTF)2PF6 were studied by all electron, periodic Hartree-Fock and hybrid density functional calculations. Electronic properties, such as the electronic band structure, the density of states and the Fermi surface are discussed in relation to the metal-insulator transition in this material. The nature of conduction is confirmed in both phases from their band structures and density of states.

Off-planar geometry and structural instability of EDO-TTF explained by using the extended debye polarizability model for bond angles.

The geometry of ethylenedioxy-tetrathiafulvalene, EDO-TTF, plays an important role in the metal-insulator transition in the charge transfer salt (EDO-TTF)(2)PF(6). The planar and off-planar geometrical conformations of the EDO-TTF molecules are explained using an extended Debye polarizability model for the bond angle. The geometrical structure of EDO-TTF is dictated by its four sulfur bond angles and these are, in turn, determined by the polarizability of the sulfur atoms.