Halogenated rhenacarboranes: optoelectronic behavior of the iodinated rhenacarborane complex anion [3,3,3-(CO) 3-8-I- closo-3,1,2-ReC 2B 9H 10] −

Abstract

Treatment of the long-known compound Cs[3,3,3-(CO) 3- closo-3,1,2-ReC 2B 9H 11] with [N(C 6H 4Br-4) 3][SbCl 6] in the presence of Me 3NO in THF (tetrahydrofuran) has led to the formation of [HNMe 3][3,3-(CO) 2-3,3-Cl 2- closo-3,1,2-ReC 2B 9H 11] in good yield. Structural characterization of this compound has identified it as a four-legged piano stool half-sandwich complex anion resulting from oxidation of rhenium by both the aminium and hexachloroantimonate ions and CO displacement promoted by Me 3NO in the presence of by-product chloride ions. Direct iodination of Cs[3,3,3-(CO) 3- closo-3,1,2-ReC 2B 9H 11] has yielded [3,3,3-(CO) 3-3-I- closo-3,1,2-ReC 2B 9H 11], which undergoes iodide migration in donor solvents from the metal to the β-B vertex in the coordinating ▪ face of the cage. The resulting complex anion, [3,3,3-(CO) 3-8-I- closo-3,1,2-ReC 2B 9H 10] −, whose structure has been confirmed by X-ray diffraction, has been shown to be luminescent in MeTHF at 77 K ( λ em = 455 nm) and electroactive in solution at ambient temperatures, undergoing a quasi-reversible two-electron oxidation to a proposed Re III cationic rhenacarborane species in MeCN solutions. By contrast, two fully reversible sequential one-electron oxidations have been observed in CH 2Cl 2 solutions.