Charge Distribution Within 1,2-Dicarba-closo-dodecaborane: Dipole Moments of Its Phenyl Derivatives

Abstract

The dipole moment of 1,2-dicarba-closo-dodecaborane is oriented with the positive end towards the carbon atoms as follows from measurements on phenyl derivatives with variable substituents. Towards the phenyl group, the substituent 1,2-C 2 B 10 H 11 behaves as a weak electron acceptor.Hofmann and Lipscomb proposed in their pioneer work 1 the experimental availability of three positional isomers of icosahedral clusters C 2 B 10 H 12 . On the basis of LCAO-MO calculations, they argued that the atomic charge on carbon atoms is positive, although simple atomic concepts such as electronegativity would have implied the opposite. The dipole moment of 1,2-C 2 B 10 H 12 (1) was determined 2 to be 4.53 D in agreement with our present measurement (4.50 D). It lies in the C 2 axis but the positions of the positive and negative ends are not evident. A comparison with the dipole moments of the bromo derivatives 3 1,2-Br 2 -1,2-C 2 B 10 H 10 and 9,12-Br 2 -1,2-C 2 B 10 H 10 should confirm qualitatively the above proposal but there is an inherent weakness that the electron distribution can be affected by the immediately bonded substituents.Our intention in this work was to gain more information about the electron distribution in the molecule of 1 by the method common in organic chemistry 4,5 -introducing, at a greater distance, non-interacting substituents with known partial dipole moments viz., in the para position of the benzene ring. Our first task was thus confirming the direction of the vector

Adsorption of oriented carborane dipoles on a silver surface

“…Our experimental measurements of the dipole moments of A , B , and of the parent 1,2‐dicarba‐ closo ‐dodecaborane (3.04 D, 4.40 D, and 3.86 D, respectively [experimental details are provided in the Supporting Information]) as well as the respective calculated values (3.7 D, 5.5 D, and 4.3 D, respectively ) show that B is a stronger dipole than A . It is worth noting that some earlier studies show the experimental value for the parent 1,2‐dicarba‐ closo ‐dodecaborane very close to the calculated one, ∼4.5 D . Despite the higher dipole moment of the isomer B compared to A , it shifts the surface potential for only ∼300 mV higher than is the reference bare Ag film.…”

Dihalogen and Pnictogen Bonding in Crystalline Icosahedral Phosphaboranes

“…The electron distribution is in disagreement with the classical electronegativity concept in multicenter bonding [5,6] and it results in areas of highly positive electrostatic potential, called σ-holes [7], on phosphorus atoms [8]. The concept of σ-hole, developed by Politzer et al, was originally used to describe halogen (X) bonds, where the σ-hole was centered on the carbon-halogen σ-bond axis.…”

Influence of Antipodally Coupled Iodine and Carbon Atoms on the Cage Structure of 9,12-I2-closo-1,2-C2B10H10: An Electron Diffraction and Computational Study

“…The 1,2-isomer (the so-called ocarbaborane with C 2v symmetry; see Figure 1 for the molecular structure) is the least stable isomer and the one with the largest dipole moment. 6 Consequently, terminal hydrogens bonded to the atoms B(9) and B(12) [antipodally coupled with C(1,2)] 7 are quite hydridic and can be easily replaced by, for example, halogens atoms or SH groups. 8 Figure 1.…”