Center for Computational Quantum Chemistry, South China Normal University, Guangzhou 510631, P.R. China.
Inorg Chem. 2010 Feb 1;49(3):1046-55. doi: 10.1021/ic901964f.
The fluoroborylene ligand (BF), isoelectronic with CO, was recently (2009) realized experimentally by Vidović and Aldridge in Cp(2)Ru(2)(CO)(4)(mu-BF). In this research the related iron carbonyl fluoroborylene complexes Fe(BF)(CO)(n) (n = 4, 3), Fe(2)(BF)(CO)(8), and Fe(2)(BF)(2)(CO)(n) (n = 7, 6) are compared with the isoelectronic Fe(CO)(n+1) and Fe(2)(CO)(n+2) as well as the thiocarbonyls Fe(CS)(CO)(n) and Fe(2)(CS)(2)(CO)(n) using density functional theory. For Fe(BF)(CO)(4) the axially and equatorially substituted trigonal bipyramidal structures are predicted to be nearly degenerate as is the case for Fe(CS)(CO)(4). The lowest energy structures for Fe(BF)(CO)(3) are derived from the trigonal bipyramidal Fe(BF)(CO)(4) structures by removal of CO groups. For the binuclear derivatives Fe(2)(BF)(CO)(8) and Fe(2)(BF)(2)(CO)(n) (n = 7, 6) structures with BF bridges are preferred energetically over structures with CO bridges. However, no structures for the unsaturated Fe(2)(BF)(2)(CO)(6) are found with four-electron donor eta(2)-mu-BF groups. This differs from the corresponding Fe(2)(CS)(2)(CO)(6) where structures with eta(2)-mu-CS groups and formal Fe-Fe single bonds are preferred over structures with only two electron donor CO and CS groups and formal Fe=Fe double bonds. The lowest energy structure for Fe(2)(BF)(2)(CO)(7) is thus predicted to be similar to the well-known triply bridged Fe(2)(CO)(9) structure but with two bridging BF groups and one bridging CO group. However, the dissociation energy of Fe(2)(BF)(2)(CO)(7) into mononuclear fragments is much higher than that of Fe(2)(CO)(9). Removal of the bridging CO group from this lowest energy Fe(2)(BF)(2)(CO)(7) structure leads to the doubly BF-bridged global minimum structure for Fe(2)(BF)(2)(CO)(6).
氟硼烯配体（BF）与 CO 等电子，最近（2009 年）由 Vidović 和 Aldridge 在 Cp(2)Ru(2)(CO)(4)(μ-BF)中实验实现。在这项研究中，相关的铁羰基氟硼烯配合物 Fe(BF)(CO)(n)（n=4,3）、Fe(2)(BF)(CO)(8)和 Fe(2)(BF)(2)(CO)(n)（n=7,6）与等电子的 Fe(CO)(n+1)和 Fe(2)(CO)(n+2)以及硫代羰基 Fe(CS)(CO)(n)和 Fe(2)(CS)(2)(CO)(n)进行了比较，使用密度泛函理论。对于 Fe(BF)(CO)(4)，轴向和赤道取代的三角双锥结构被预测为几乎简并，与 Fe(CS)(CO)(4)的情况相同。Fe(BF)(CO)(3)的最低能量结构源自三角双锥 Fe(BF)(CO)(4)结构，通过去除 CO 基团。对于双核衍生物 Fe(2)(BF)(CO)(8)和 Fe(2)(BF)(2)(CO)(n)（n=7,6），具有 BF 桥的结构在能量上优于具有 CO 桥的结构。然而，对于不饱和的 Fe(2)(BF)(2)(CO)(6)，没有发现具有四电子供体 eta(2)-mu-BF 基团的结构。这与相应的 Fe(2)(CS)(2)(CO)(6)不同，其中具有 eta(2)-mu-CS 基团和形式 Fe-Fe 单键的结构优先于仅具有两个电子供体 CO 和 CS 基团和形式 Fe=Fe 双键的结构。因此，预测 Fe(2)(BF)(2)(CO)(7)的最低能量结构类似于众所周知的三桥接 Fe(2)(CO)(9)结构，但具有两个桥接 BF 基团和一个桥接 CO 基团。然而，Fe(2)(BF)(2)(CO)(7)分解为单核片段的离解能远高于 Fe(2)(CO)(9)。从这个最低能量的 Fe(2)(BF)(2)(CO)(7)结构中去除桥接 CO 基团会导致 Fe(2)(BF)(2)(CO)(6)的双 BF 桥接全局最小结构。
