Department of Chemistry, University of Calgary, Calgary, Alberta, Canada T2N1N4.
Inorg Chem. 2012 Jul 16;51(14):7794-800. doi: 10.1021/ic300824u. Epub 2012 Jun 25.
The nature of the putative Cr-Cr quintuple bond in Ar'CrCrAr' (Ar' = C(6)H(3)-2,6(C(6)H(3)-2,6-Pr(i)(2))(2)) is investigated with the help of a newly developed energy and density decomposition scheme. The new approach combines the extended transition state (ETS) energy decomposition method with the natural orbitals for chemical valence (NOCV) density decomposition scheme within the same theoretical framework. The results show that in addition to the five bonding components (σ(2)π(2)π'(2)δ(2)δ'(2)) of the Cr-Cr bond, the quintuple bond is augmented by secondary Cr-C interactions involving the Cr-ipso-carbon of the flanking aryl rings. The presence of isopropyl groups (Pr(i)) is further shown to stabilize Ar'CrCrAr' by 20 kcal/mol compared to the two Ar'Cr monomers through stabilizing van der Waals dispersion interactions.
在 Ar'CrCrAr'(Ar' = C(6)H(3)-2,6(C(6)H(3)-2,6-Pr(i)(2))(2)) 中,假定的 Cr-Cr 五重键的性质是通过新开发的能量和密度分解方案来研究的。新方法将扩展过渡态(ETS)能量分解方法与自然轨道化学价(NOCV)密度分解方案结合在同一个理论框架内。结果表明,除了 Cr-Cr 键的五个成键分量(σ(2)π(2)π'(2)δ(2)δ'(2))外,五重键还通过涉及侧翼芳环的 Cr-ipso-碳原子的次级 Cr-C 相互作用得到增强。进一步表明,与两个 Ar'Cr 单体相比,异丙基(Pr(i))的存在通过稳定范德华色散相互作用将 Ar'CrCrAr'稳定 20 kcal/mol。