Key Laboratory of Cluster Science, Ministry of Education of China, Department of Chemistry, Beijing Institute of Technology, Beijing, 100081, PR China.
Dalton Trans. 2011 Jul 14;40(26):6922-8. doi: 10.1039/c1dt10508f. Epub 2011 Jun 2.
The first binuclear sandwich-like complexes based on the aromatic tetraatomic species with formula M(2)(η(4)-E(4))(2) (M = Al, Ga; E = N, P, As) have been studied by density functional theory (DFT). The stable conformer for each M(2)(η(4)-E(4))(2) is the staggered one with D(4d) symmetry except for Ga(2)(η(2)-N(4))(2) with C(2v) symmetry. Natural bonding orbital (NBO) analysis indicates that the metal-metal bonds of Al(2)(η(4)-E(4))(2) (E = N, P, As) and Ga(2)(η(4)-E(4))(2) (E = P, As) are all σ single bonds, which are derived mostly from the s and p(z) orbitals of the metal atoms by molecular orbital (MO) analysis. For M(2)(η(4)-E(4))(2) (M = Al, Ga; E = P, As), the metal-ligand interactions are covalent, while for Al(2)(η(4)-N(4))(2) the interactions between the Al atoms and the N(4)(2-) ligands are ionic. According to the calculated dissociation energies for breaking metal-metal bonds, the Al-Al and Ga-Ga bonds are very strong indicating that these stable sandwich-like compounds Al(2)(η(4)-E(4))(2) (E = N, P, As) and Ga(2)(η(4)-E(4))(2) (E = P, As) may be synthesized in future experiments. The nitrogen-rich compounds Al(2)(η(4)-N(4))(2) and Ga(2)(η(2)-N(4))(2) may be used as potential candidates of high energy density materials (HEDMs). Nucleus-independent chemical shifts (NICS) values reveal that the E(4)(2-) rings in the Al(2)(η(4)-E(4))(2) (E = N, P, As) and Ga(2)(η(4)-E(4))(2) (E = P, As) species possess conflicting aromaticity (σ antiaromaticity and π aromaticity) and with the same ligands, the E(4)(2-) ligands in Ga(2)(η(4)-E(4))(2) have more aromaticity than those in Al(2)(η(4)-E(4))(2).
基于具有公式 M(2)(η(4)-E(4))(2)（M = Al、Ga；E = N、P、As）的芳香四原子物种的第一个双核夹心型配合物已通过密度泛函理论（DFT）进行了研究。每个 M(2)(η(4)-E(4))(2)的稳定构象均为交错构象，具有 D(4d)对称性，除 Ga(2)(η(2)-N(4))(2)具有 C(2v)对称性。自然键轨道（NBO）分析表明，Al(2)(η(4)-E(4))(2)（E = N、P、As）和 Ga(2)(η(4)-E(4))(2)（E = P、As）的金属-金属键均为 σ 单键，这主要是由金属原子的 s 和 p(z)轨道通过分子轨道（MO）分析衍生而来。对于 M(2)(η(4)-E(4))(2)（M = Al、Ga；E = P、As），金属-配体相互作用是共价的，而对于 Al(2)(η(4)-N(4))(2)，Al 原子和 N(4)(2-)配体之间的相互作用是离子的。根据金属-金属键断裂的计算解离能，Al-Al 和 Ga-Ga 键非常强，表明这些稳定的夹心型化合物 Al(2)(η(4)-E(4))(2)（E = N、P、As）和 Ga(2)(η(4)-E(4))(2)（E = P、As）可能在未来的实验中合成。富氮化合物 Al(2)(η(4)-N(4))(2)和 Ga(2)(η(2)-N(4))(2)可能可用作高能密度材料（HEDM）的潜在候选物。核独立化学位移（NICS）值表明，Al(2)(η(4)-E(4))(2)（E = N、P、As）和 Ga(2)(η(4)-E(4))(2)（E = P、As）物种中的 E(4)(2-)环具有矛盾的芳香性（σ 反芳香性和 π 芳香性），并且在具有相同配体的情况下，Ga(2)(η(4)-E(4))(2)中的 E(4)(2-)配体比 Al(2)(η(4)-E(4))(2)中的 E(4)(2-)配体具有更多的芳香性。
