State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing, 100081, P.R. China.
Dalton Trans. 2012 May 21;41(19):5869-78. doi: 10.1039/c2dt12149b. Epub 2012 Mar 28.
Density functional theory studies on the all non-metal homodinuclear and heterodinuclear sandwich-like compounds C(2)(η(3)-L(3))(2) and BN(η(3)-L(3))(2) (L = BCO, BNN and CBO) have been performed. The staggered conformations of both C(2)(η(3)-L(3))(2) and BN(η(3)-L(3))(2) are predicted to be stable. The non-metal direct C-C and B-N bonds are covalent with σ interactions, which are formed by the interactions of s and p(z) orbitals of the center atoms. Different from the ionic metal-ligand bond in the traditional metal center sandwich-like compounds, the C-L, B-L, and N-L bonds are covalent in these all non-metal sandwich-like compounds. The NICS values indicate that the ligands of C(2)(η(3)-L(3))(2) and BN(η(3)-L(3))(2), as well as their bare rings, display multiple aromaticity (σ and π aromaticity). Both σ and π aromaticity of the ring ligands towards the center atoms become stronger after complexation with the center atoms, while the π aromaticity against the center atoms is reduced. The π aromaticity of the ligands bonded to different center atoms follows a trend of B > C > N, and the (CBO)(3)(+) ligands bonded to B possess the strongest π aromaticity. The dissociation reactions and possible synthetic reactions analysis show that these all non-metal sandwich-like compounds are stable, and the homodinuclear species are more stable than the heterodinuclear ones. These all non-metal binuclear sandwich-like compounds can be regarded as potential synthetic targets according to the highly negative free energies of the possible synthetic reactions. The isomerization reactions demonstrate that the CBO-based compounds should be more possible to synthesize in experiments than their BCO-based isomers.
已对全非金属同核和异核夹心型化合物 C(2)(η(3)-L(3))(2)和 BN(η(3)-L(3))(2)（L = BCO、BNN 和 CBO）进行了密度泛函理论研究。预测 C(2)(η(3)-L(3))(2)和 BN(η(3)-L(3))(2)的交错构象都是稳定的。非金属直接 C-C 和 B-N 键是具有 σ 相互作用的共价键，由中心原子的 s 和 p(z)轨道相互作用形成。与传统金属中心夹心型化合物中的离子金属-配体键不同，C-L、B-L 和 N-L 键在这些全非金属夹心型化合物中是共价的。NICS 值表明，C(2)(η(3)-L(3))(2)和 BN(η(3)-L(3))(2)的配体及其裸露环具有多种芳香性（σ 和 π 芳香性）。配体与中心原子配位后，对中心原子的 σ 和 π 芳香性增强，而对中心原子的 π 芳香性减弱。与不同中心原子键合的配体的 π 芳香性遵循 B > C > N 的趋势，与 B 键合的 (CBO)(3)(+)配体具有最强的 π 芳香性。离解反应和可能的合成反应分析表明，这些全非金属夹心型化合物是稳定的，同核物种比异核物种更稳定。根据可能的合成反应的高度负自由能，这些全非金属双核夹心型化合物可以被视为潜在的合成目标。互变异构反应表明，在实验中应该更容易合成基于 CBO 的化合物，而不是基于 BCO 的异构体。
