Reactivity of Lewis acids towards nitriles; crystal structure and electron deformation density of C2N2·SbF5 and photoelectron spectrum of AsF5

Abstract

The reactivity of nitriles and dinitriles HCN, C₂N₂, CCl₂(CN)₂ and CH₂(CN)₂ towards AsF₅ and SbF₅ has been investigated. The new compounds HCN·AsF₅1, HCN·SbF₅2, C₂N₂·AsF₅3, C₂N₂·SbF₅4, CH₂(CN)₂·AsF₅5, CH₂(CN)₂·(2AsF₅)6 and CCl₂(CN)₂·AsF₅7 have been characterized by chemical analysis, IR, Raman, ¹H, ¹⁹F and ¹⁴N NMR spectroscopy. The crystal structure of the first example of a cyanogen adduct C₂N₂·SbF₅4 has been determined. Compound 4 crystallizes in the orthorhombic space group C222₁ with cell parameters a= 6.579(1), b= 16.245(1) and c= 6.389(1)Å. The deformation density of the molecule was examined. The reactivities of HCN and C₂N₂ towards the strong Lewis acid AsF₅ are discussed on the basis of the hard–soft acid–base principle. The hitherto unknown ionization potential of AsF₅(15.57 eV) was obtained by photoelectron spectroscopy. A semiquantitative molecular orbital scheme for AsF₅ is presented.