Institute of Chemical Physics, Beijing Institute of Technology, Beijing, 100081, People's Republic of China.
J Mol Model. 2012 Aug;18(8):3577-86. doi: 10.1007/s00894-012-1362-y. Epub 2012 Feb 16.
A series of all-metal binuclear sandwich-like complexes with the formula M(2)(η(4)-E(4))(2) (M=Al, Ga, In; E=Sb, Bi) was studied by density functional theory (DFT). The most stable conformer for each of the M(2)(η(4)-E(4))(2) species is the staggered one with D (4d) symmetry. The centred metal-metal bond in each M(2)(η(4)-E(4))(2) species is a covalent single bond, with the main contributors to these covalent bonds being the a(1) and e orbitals. For all these species, the interactions between the centred metal atoms and the all-metal ligands are covalent; η(4)-Sb (4) (2-) has a stronger ability to stabilize metal-metal bonds than η(4)-Bi (4) (2-). Nucleus-independent chemical shifts (NICS) values and molecular orbital (MO) analysis reveal that the all-metal η(4)-Sb (4) (2-) and η(4)-Bi (4) (2-) ligands in M(2)(η(4)-E(4))(2) possess conflicting aromaticity (σ antiaromaticity and π aromaticity), which differs from the all-metal multiple aromatic unit Al (4) (2-). In addition, all of these M(2)(η(4)-E(4))(2) species are stable according to the dissociation energies of M(2)(η(4)-E(4))(2) → 2 M(η(4)-E(4)) and M(2)(η(4)-E(4))(2) → 2 M + 2E(4), and these stable species can be synthesized by two-step substitution reactions: CpZnZnCp + 2E (4) (2-) → E(4)ZnZnE(4) + 2Cp(-) and E(4)ZnZnE(4) + 2 M (2) (+) → E(4)MME(4) + 2Zn(+).
一系列通式为 M(2)(η(4)-E(4))(2)(M=Al、Ga、In;E=Sb、Bi)的全金属双核夹心型配合物,采用密度泛函理论(DFT)进行了研究。每个 M(2)(η(4)-E(4))(2)物种最稳定的构象是具有 D (4d)对称性的交错构象。每个 M(2)(η(4)-E(4))(2)物种的中心金属-金属键是一个共价单键,这些共价键的主要贡献者是 a(1)和 e 轨道。对于所有这些物种,中心金属原子与全金属配体之间的相互作用是共价的;η(4)-Sb (4) (2-)比 η(4)-Bi (4) (2-)具有更强的稳定金属-金属键的能力。核独立化学位移(NICS)值和分子轨道(MO)分析表明,全金属 η(4)-Sb (4) (2-)和 η(4)-Bi (4) (2-)配体在 M(2)(η(4)-E(4))(2)中具有相互矛盾的芳香性(σ反芳香性和π芳香性),这与全金属多芳香单元 Al (4) (2-)不同。此外,根据 M(2)(η(4)-E(4))(2)→2 M(η(4)-E(4))和 M(2)(η(4)-E(4))(2)→2 M(+) + 2 E(4)的离解能,所有这些 M(2)(η(4)-E(4))(2)物种都是稳定的,这些稳定的物种可以通过两步取代反应合成:CpZnZnCp + 2 E (4) (2-)→E(4)ZnZnE(4) + 2 Cp(-)和E(4)ZnZnE(4) + 2 M (2) (+)→E(4)MME(4) + 2Zn(+)。