Striking Borane Planarization in the Thermal Rearrangement (η-CH)Fe(η-BH)→(η-CH)Fe(η-BH).

In 1977 Weiss and Grimes, by means of mass spectrometry and H and B NMR spectroscopy, proposed two structures (I and II) for the ferraborane (η-CH)Fe(BH), isoelectronic with ferrocene. In this work, by means of high-level quantum-chemical computations, we confirm the experimental structures of the two isomers with their corresponding energies, and assign the reported H and B NMR chemical shifts. A striking result from this study is the planarization (3D→2D) of the BH ligand - an unknown isolated anion, isoelectronic with aromatic cyclopentadienyl anion CH - when attached to the (η-CH)Fe moiety, thus resulting in a more stable ferraborane isomer II.

Bowl-shaped Cluster CuB : A Viable Global Minimum with Twofold Aromaticity.

A low-lying structure is revealed for the CuB cluster, which is bowl-shaped. It consists of a triangular CuB base and a B rim. Molecular dynamics simulations indicates its structural robustness; at an elevated temperature (600 K), the base rotates reversibly within the B perimeter.