The Role of C–H···H–B Interactions in Establishing Rotamer Configurations in Metallabis(dicarbollide) Systems

Abstract

The aim of this work is to explore the self-interaction capability of the anion [3,3Ј-Co(1,2-C 2 B 9 H 11 ) 2 ] -through C cluster -H···H-B (C c -H···H-B) dihydrogen bonds. A set of theoretical and empirical data aiming to establish the main rules that account for the binding mode between the negatively charged borane framework made by [3,3Ј-Co(1,2-C 2 B 9 H 11 ) 2 ] -and the [NMe 4 ] + ions have been compiled. The interaction between cation and anion is mainly electrostatic but the covalent contribution is also proven and quantified. The exi-

Atomistic Simulations of COSAN: Amphiphiles without a Head‐and‐Tail Design Display “Head and Tail” Surfactant Behavior

“…The transoid rotamer is the one with lower energy “in vacuo”, as shown by quantum chemical calculations . However, a previous study conducted by some of us found that this rotamer is only present at about 8 % in crystal structures with the composition M[Co(C 2 B 9 H 11 ) 2 ]. Largely, the most abundant rotamer in the solid state is the cis rotamer (Table ).…”

“…However, it is also known that one of the specific rotameric forms of COSAN (the cisoid rotamer, see Figure ) has a charge distribution resembling that of an anionic surfactant, with a polar region (concentrating most of the anion charge) and an apolar region. Another key aspect is that small changes in the structure of COSAN that block particular rotameric forms lead to different self‐assembled structures .…”

Nonclassical Hydrophobic Effect in Micellization: Molecular Arrangement of Non‐Amphiphilic Structures

“…[15] In the solid state, however, the cisoid form was preferred due to the mutual contacts of the metallacarborane clusters surrounded by innocent counterions. [16] The rotational profiles of the clusters in the matrix composed of "soft matter" (e.g., proteins or synthetic polymers) emphasize the eminent role of the environment in determining the rotamer preferences. [11,17] Thus, all of the isomers (cisoid, gauche, and transoid) should be taken into consideration in aqueous solutions.…”

Metallacarboranes and their interactions: theoretical insights and their applicability

“…Concerning hydrogen atoms, when these are bonded to carbon atoms are more acidic than when are bonded to boron atoms, which are found to be hydridic, despite their atomic charge is near zero. 43 There have been attempts to rationalize the reactivity of different boron vertices by considering the atomic charges. However, many reactions in boranes can be better interpreted considering that the attack takes place on the B-H bond and not on the H or B atoms.…”

“…However, theoretical calculations predict the transoid rotamer as the most stable, while in the solid-state crystallographic structures show a clear tendency for the cisoid arrangement. 43 This anomaly is probably caused by the fact that cobaltabisdicarbollide anions interact with each other using the positively and negatively charged regions on the cluster. The cisoid rotamer would be stabilized via electrostatic dihydrogen bonding, intermolecular C-H···H-B interactions where the partial charge of the proton in C-H could be a good indicator to discern the rotamer disposition found in the solid state.…”