Proton Affinities of Cationic Carbone Adducts [AC(PPh3)2]+ (A=Halogen, Hydrogen, Methyl) and Unusual Electronic Structures of the Cations and Dications [AC(H)(PPh3)2]2+

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• 作者：Prof. Dr. Wolfgang Petz ; Dr. Istemi Kuzu ; Prof. Dr. Gernot Frenking ; Dr. Diego M. Andrada ; Prof. Dr. Bernhard Neumü ; ller ; Maximilian Fritz and Jö ; rn E. Mü ; nzer
• 刊名：Chemistry - A European Journal
• 出版年：2016
• 出版时间：June 13, 2016
• 年：2016
• 卷：22
• 期：25
• 页码：8536-8546
• 全文大小：2406K
• ISSN：1521-3765

文摘

This work reports the syntheses and the first crystal structures of the cationic carbone adducts [FC(PPh₃)₂]⁺ and [BrC(PPh₃)₂]⁺ and the protonated dication [FC(H)(PPh₃)₂]²⁺, which are derived from the carbone C(PPh₃)₂. Quantum chemical calculations and bonding analyses were carried out for the series of cations [AC(PPh₃)₂]⁺ and dications [AC(H)(PPh₃)₂]²⁺, where A=H, Me, F, Cl, Br, I. The bonding analysis suggests that the cations are best described as phosphane complexes L→(CA)⁺←L (L=PPh₃), which are related to the neutral borylene adducts L→(BA)←L (L=cyclic carbene; A=H, aryl) that were recently isolated. The carbone adducts [AC(PPh₃)₂]⁺ possess a π electron lone pair at carbon and they can easily be protonated to the dications [AC(H)(PPh₃)₂]²⁺. The calculations of the dications indicate that the molecules are best represented as complexes L→(CHA)²⁺←L (L=PPh₃) where a carbene dication is stabilized by the ligands. The central carbon atom in the cations and even in the dications carries a negative partial charge, which is larger than the negative charge at fluorine. There is also the peculiar situation in which the carbon–fluorine bonds in [FC(PPh₃)₂]⁺ and [FC(H)(PPh₃)₂]²⁺ exhibit the expected polarity with the negative end at fluorine, but the carbon atom has a larger negative charge than fluorine. Given the similarity of carbodiphosphorane C(PPh₃)₂ and carbodicarbene C(NHC)₂, we expect that analogous compounds [AC(NHC)₂]⁺ and [AC(H)(NHC)₂]²⁺ with similar features as [AC(PPh₃)₂]⁺ and [AC(H)(PPh₃)₂]²⁺ can be isolated.