Cr鈥揅r Quintuple Bonds: Ligand Topology and Interplay Between Metal鈥揗etal and Metal鈥揕igand Bonding

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• 作者：Andr茅s Falceto ; Klaus H. Theopold ; Santiago Alvarez
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：November 16, 2015
• 年：2015
• 卷：54
• 期：22
• 页码：10966-10977
• 全文大小：575K
• ISSN：1520-510X

文摘

Chromium鈥揷hromium quintuple bonds seem to be approaching the lower limit for their bond distances, and this computational density functional theory study tries to explore the geometrical and electronic factors that determine that distance and to find ways to fine-tune it via the ligand choice. While for monodentate ligands the Cr鈥揅r distance is predicted to shorten as the Cr鈥揅r鈥揕 bond angle increases, with bridging bidentate ligands the trend is the opposite, since those ligands with a larger number of spacers between the donor atoms favor larger bond angles and longer bond distances. Compared to Cr鈥揅r quadruple bonds, the quintuple bonding in Cr₂L₂ compounds (with L a bridging bidentate N-donor ligand) involves a sophisticated mechanism that comprises a positive pyramidality effect for the 蟽 and one 蟺 bond, but a negative effect for one of the 未 bonds. Moreover, the shorter Cr鈥揅r distances produce a mismatch of the bridging ligand lone pairs and the metal acceptor orbitals, which results in a negative correlation of the Cr鈥揅r and Cr鈥揘 bond distances in both experimental and calculated structures.