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The resonance energy for hexazine was calculated to be 97.8 kJ mol −1 and was greater than the corresponding value for benzene (81.4 kJ mol −1). The results indicated that all homonuclear structures, including hexazine, resemble benzene and are characterized with resonance between two Kekulé structures. Magnetic properties for the studied structures were obtained at the coupled HF level, within the CTOCD-DZ formalism, using the 6-3IG(d,p) basis set, leading to maps for the α, π and the (α + π) contributions to the current density. The valence bond calculations were conducted at the VB/6-31G(d,p) level of theory, on B3LYP optimized structures, using TURTLE as implemented in the GAMESS-UK package. Valence bond theory and ring current maps were used to study the electronic structure of several homo- or heterocyclic benzene analogs, including hexazine N 6 (D 6h). Benin, in Comprehensive Heterocyclic Chemistry III, 2008 9.13.13 Further Developments 4 + adopts a trigonal prismatic structure (D 3h) similar to that of prismane, C 6H 6, an isomer of benzene. Match the AOs on nickel with the appropriate SALCs of the two allyl groups, looking for the best match from those available. Identify the symmetry labels for the 4 s-, 4 p- and 3 d-AOs on nickel. (Hint : since the SALCs have a or b labels, this can be done by treating each SALC as a complete unit, counting 1, 0, -1 if it is unmoved, moves or is reversed for each operation).
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The bonding in the bis-allyl complex η 3-(C 3H 5) 2Ni (C 2h) is complex due to a large degree of mixing between AOs and SALCs.
![gaussview 6 point group symmetry gaussview 6 point group symmetry](https://i.ytimg.com/vi/17QpHFoQKMM/maxresdefault.jpg)
It should, however, be emphasized that while it is didactically useful to formulate the bonding of actinide-arene complexes in terms of well-defined electron transfer to the arene, the resulting actinide-arene bonding interactions exhibit appreciable covalency, so such book-keeping should be recognized as being a formal exercise rather than a literal manifestation while assigning oxidation states to metal ions in such bonding scenarios is useful to rationalizing their bonding and reactivity, it becomes a somewhat moot point. The accessibility of the ψ 4 and ψ 5 arene orbitals allows various levels of reduction of arenes, to formally monoanionic (7 π-electron), dianionic (8π-electron) and tetranionic (10π-electron) species, with the formal 8π- and 10π-electron ligand charge states being the most common for actinide-arene complexes, as found in inverse sandwich complexes (see below). Since the principal metal-ligand bonding interactions of actinide-arene complexes tends to be dominated by δ-bonding character, σ- and π-bonding combinations tend to play a lesser role than for smaller ring sizes. Unlike in C 4-ligands, where the vacant δ-symmetry ψ 4 is energetically high-lying, the vacant ψ 4 and ψ 5 orbitals of C 6 arenes are relatively low-lying and energetically reasonably well-suited to bonding with early actinide frontier orbitals thus, as will become clear in this Chapter, arene δ-bonding to actinides plays a major role in actinide-arene chemistry. Unique to the actinides, φ bonding is also possible through the high-lying, vacant ψ 6 orbital, though for generally poor energetic matching reasons this bonding mode plays a lesser role in actinide-arene chemistry. The frontier orbitals of C 6 arenes are of the correct symmetry to participate in σ (ψ 1), π (ψ 2 and ψ 3), and δ (ψ 4 and ψ 5) bonding with a metal center, Fig. The symmetry of C 6 arenes can be described using the D 6h point group, and in the neutral form contains 6π-electrons, thus satisfying Huckel's rule (4n + 2 π-electrons) for aromaticity.