The singlet–triplet gap of the halonitrenium ions NHX+, NX2+ and the halocarbenes CHX, CX2(X = F, Cl, Br, I)

Abstract

Ab initio studies at the MP4/6–311 G(2df)//MP2/6–31 G(D) level of theory using effective core potentials for Br and I predict, that halonitrenium ions Nx₂⁺ and NHX⁺(X = F, Cl, Br, I) have a (¹A₁) singlet ground state and a singlet-triplet gap between 57–12 for NX₂⁺ and 8–4 kcal mol^–1(1 cal = 4.184 J) for NHX⁺; a comparison of experimental and theoretical results of the isoelectronic carbenes shows that the theoretical level is quite reliable.