Synthesis and reactivity of o-carboranyl-I(OTf)2 and -I(X)(OTf) reagents: triflation of C1 chlorocarbons, arene iodo-o-carboranylation, and unsaturation of n-alkanes

Abstract

Investigation of the recently reported ortho-carboranyl iodine(III) compound, 1I(OTf)₂ (1I = 1-iodo-2-methyl-8,9,10,12-tetrachloro-o-carborane), a species previously only observed in solution, has resulted in an improved synthesis via Si(OTf)₄ and 1IF₂ allowing its isolation as a stable solid, with the intermediate complex 1I(F)(OTf) also isolable. Further study of 1I(OTf)₂ revealed it abstracts chloride from C₁ halocarbons (CH₂Cl₂, CHCl₃) to form previously unknown triflate esters, TfO-CHCl₂ and TfO-CH₂Cl. Computational and reactivity studies suggest the intermediacy of unstable 1I(Cl)(OTf), and show abstracted chloride is ultimately oxidized to Cl₂. 1I(OTf)₂ is later found to react with an arene (BrPh) to form a C-I⁺-C aryl-carboranyl iodonium salt, and with C_≥3 alkanes under ambient temperature and pressure (1–72 h) to form mixed unsaturated products through a predicted –I(Alk)(OTf) intermediate.