Abstract: Three isomers of the allyl cation C3H5+ were obtained in salts with the carborane anion CHB11Cl11-. Two of them, angular CH3-CH═CH+ (I) and linear CH3-C+═CH2 (II), were characterized by X-ray crystallography, and the third one, (CH2CHCH2)+ (III), is formed in an amorphous salt. The stretch vibration of the charged double bond C═C+ of I and II is decreased by 162 cm-1 (I) or 76 cm-1 (II) as compared to that of neutral propene. This result contradicts the prediction of DFT and MP2 calculations with the 6-311G++(d,p) basis set that the appearance of the positive charge on the C═C bond should increase its stretch vibration by 200 cm-1 (I) or 210 cm-1 (II). According to infrared spectra, the CC bonds in isomer III have one-and-a-half bond status. Isomers I and II in the crystal lattice are stabilized due to uniform ionic interactions with neighboring anions with partial transfer of a positive charge to them. Additional stabilization of II is provided by a weak hyperconjugation effect. Isomer III is stabilized in the amorphous phase due to ion paring with a counterion and a strong intramolecular hyperconjugation effect. © 2021 The Authors. Published by American Chemical Society.

Cite: Stoyanov E.S. , Bagryanskaya I.Y. , Stoyanova I.V.
Isomers of the Allyl Carbocation C3H5+in Solid Salts: Infrared Spectra and Structures
ACS Omega. 2021. V.6. N37. P.23691–23699. DOI: 10.1021/acsomega.1c01316 WOS Scopus РИНЦ

Identifiers:

Web of science	WOS:000699954000006
Scopus	2-s2.0-85115647024
Elibrary	47104808
OpenAlex	W3200912306

Altmetrics: