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+. Issue 25 (11th May 2016)

• Record Type: Journal Article
• Authors: Petz, Wolfgang; Kuzu, Istemi; Frenking, Gernot; Andrada, Diego M.; Neumüller, Bernhard; Fritz, Maximilian; Münzer, Jörn E.
• Is Part Of: Chemistry. Volume 22:Issue 25(2016)
• Page Start: 8536
• Page End: 8546
• Publication Date: 2016-05-11
• Subjects: bonding analysis -- carbone adducts -- proton affinities -- quantum chemical calculations; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201600525
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: 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. Abstract : Cationic carbone adducts : The structurally characterized cations [FC(PPh3 )2 ] + and [BrC(PPh3 )2 ] + and the protonated dication [FC(H)(PPh3 )2 ] 2+ possess unusual electronic structures and peculiar charge distributions (see scheme).