The ubiquitous icosahedral B<SUB>12</SUB> in boron chemistry

Though boranes exhibit a wide variety of polyhedral structures, all the three polymorphs of elemental boron essentially contain icosahedral B12 units as the predominant building block in their unit cell. Theoretical and experimental studies on boranes show that the icosahedral arrangement leads to most stable boranes and borane anions. This paper attempts to explain the phenomenal stability associated with the icosahedral B12 structure. Using fragment molecular orbital theory, the remarkable stability of B12H2-12 amongcloso boranes are explained. The preferential selection icosahedral B12 unit by elemental boron is explained by improvising a contrived B84 sub-unit of the &#946;-rhombohedron, the most stable polymorph. This also leads to a novel covalent way of stuffing fullerenes with icosahedral symmetry

Ab initio predictions on novel stuffed polyhedral boranes

This article does not have an abstract

Electronic requirements of polycondensed polyhedral boranes

This article does not have an abstract

Alternatives for Epoxides in Graphene Oxide

All input geometries corresponding to "Alternatives for epoxides in Graphene Oxide " are given here

A unifying electron-counting rule for macropolyhedral boranes, metallaboranes, and metallocenes

A generally applicable electron-counting rule-the mno rule-that integrates macropolyhedral boranes, metallaboranes, and metallocenes and any combination thereof is presented. According to this rule, m+n+o number of electron pairs are necessary for a macropolyhedral system to be stable. Here, m is the number of polyhedra, n is the number of vertices, and o is the number of single-vertex-sharing condensations. For nido and arachno arrangements, one and two additional pairs of electrons are required. Wade's n+1 rule is a special case of the mno rule, where m = 1 and o = 0. B20H16, for example has m = 2 and n = 20, leading to 22 electron pairs. Ferrocene, with two nido polyhedral fragments, has m = 2, n = 11, and o = 1, making the total 2+11+1+2 = 16. The generality of the mno rule is demonstrated by applying it to a variety of known macropolyhedral boranes and heteroboranes. We also enumerate the various pathways for condensation by taking icosahedral B12 as the model. The origin of the mno rule is explored by using fragment molecular orbitals. This clearly shows that the number of skeletal bonding molecular orbitals of two polyhedral fragments remains unaltered during exohedral interactions. This is true even when a single vertex is shared, provided the common vertex is large enough to avoid nonbonding interactions of adjacent vertices on either side. But the presence of more than one common vertex results in the sharing of surface orbitals thereby, reducing the electronic requirements

Missing hydrogens in B<SUB>19</SUB>H<SUB>20</SUB><SUP>-</SUP>? application of electron counting rule for edge-sharing macropolyhedral boranes

This article does not have an abstract

Nature of Interactions between Boron Clusters: Extended Delocalization and Retention of Aromaticity post Oxidation

Polyhedral boron clusters are lauded as 3D-aromatic that frequently form interconnected periodic networks in boron-rich borides with metal and non-metals having high thermodynamic stability and hardness. This leads to the question of whether the spherical delocalization of electrons in these clusters is extended across the network as in organic aromatic networks. These borides also frequently show partial oxidation, having fewer electrons than that is mandated by electron counting rules, whose impact on their aromatic stability and geometry remains mysterious. Understanding the nature of electronic communication between polyhedra in polyhedral borides is largely unknown though it is crucial for the rational design of advanced materials with desirable mechanical, electronic and optical properties. Here we show that electronic delocalization across polyhedral clusters has a significant impact on their structure and stability. Our computational inquiry on closo borane dimers shows substantial variation in conjugation with the ideal electron count. Upon two-electron oxidation, instead of forming exohedral multiple bonding that disrupts the aromaticity, it undergoes subtle geometric transformations that conserve aromaticity. The nature of geometric transformation depends on the HOMO that is decided locally on the polyhedral degree of the interacting vertices. The prevalence of π-type interactions as HOMO in tetravalent vertices encourage conjugation across clusters and turn into a macropolyhedral system hosting a rhombic linkage between clusters upon oxidation. In contrast, the σ-type interactions dominate the HOMO of pentavalent vertices that prefers to confine aromaticity within the polyhedra by separating them with localized 3c-2e bonds. Our findings expose the fundamental bonding principles that govern the interaction between boron clusters and will provide chemical guidance for the design and analysis of polyhedral boride networks with desired properties