Departamento de Física y Química Teórica, DEPg. Facultad de Química, Universidad Nacional Autónoma de México, México D. F., C. P. 04510, México.
J Phys Chem A. 2010 Dec 30;114(51):13303-12. doi: 10.1021/jp1086174. Epub 2010 Dec 8.
Using the gradient-corrected BPW91 method and 6311++G(2d,2p) basis sets, it was found that adsorption of benzene by iron atoms forms a multiple-decker sandwich (MDS) geometry for the ground state (GS) of Fe(2)-(C(6)H(6))(3), as Fe(2) is broken. Though decoordination occurs, the ligands are bonded symmetrically to the Fe sites by η(6) (for the two external rings) and two η(3) (for the central ring) Fe-C coordinations; this big amount of Fe-C bonds enhances the stability of the MDS GS. This is unexpected, as the experiment suggests MDS for TM(n)-(C(6)H(6))(m) species of earlier transition metals (TMs) and clusters covered with benzene, i.e., rice-ball (RB) structures, for late 3d atoms. However, preserving Fe(2), an RB state was found, quasi-degenerate with the GS, with a smaller amount of Fe-C contacts and a stronger Fe(2) bond. The MDS shows higher stability for electron attachment and deletion events, but its adiabatic electron affinity, 1.11 eV, differs more from the experiment (0.80 ± 0.1 eV) than the one (0.97 eV) for RB. Thus, MDS and RB states can appear in a sample of Fe(2)-(C(6)H(6))(3). Like the electron affinity, the ionization energy of the complex is also smaller than those of the metal and benzene moieties, but closer to the former, signifying that the electron, delocalized through the 3d-π bonds, is mainly deleted from the metallic units.
使用梯度校正 BPW91 方法和 6-311++G(2d,2p)基组，发现铁原子吸附苯形成了多层夹心（MDS）几何形状，这是 Fe(2)-(C(6)H(6))(3)基态（GS）的特征，因为 Fe(2)被破坏。尽管配位发生了，但配体通过η(6)（对于两个外部环）和两个η(3)（对于中心环）Fe-C 配位对称地键合到 Fe 位点上；这种大量的 Fe-C 键增强了 MDS GS 的稳定性。这是出乎意料的，因为实验表明，对于早期过渡金属（TMs）和被苯覆盖的团簇的 TM(n)-(C(6)H(6))(m)物种，MDS 是稳定的，而对于较晚的 3d 原子，则是饭团（RB）结构。然而，保留 Fe(2)，发现了一个准简并的 RB 态，与 GS 相比，Fe-C 接触较少，Fe(2)键更强。MDS 对电子附加和删除事件表现出更高的稳定性，但它的绝热电子亲和能为 1.11 eV，与实验值（0.80±0.1 eV）的差异比 RB 的（0.97 eV）更大。因此，MDS 和 RB 态可能同时存在于 Fe(2)-(C(6)H(6))(3)样品中。与电子亲和能一样，该络合物的电离能也小于金属和苯部分的电离能，但更接近金属部分，这表明电子通过 3d-π 键离域，主要从金属单元中删除。
