The reactivity of cationic [trioxo-(1,4,7-triazacyclononane) rhenium(VII)] and oxorhenium(V) complexes containing triazamacrocycles

The reduction of colourless LRe^VIIO₃]Br in an acetone-water mixture (6: 1) with zinc amalgam affords green, air-sensitive LRe^VO₂Br] which forms a violet complex LReO(μ-O)₂ReOBr₂]in aqueous solution (L = 1,4,7-triazacyclononane; C₆H₁₅N₃). From a similar reduction of LReO₃]ReO₄ the violet neutral complex LReO(μ-O)₂ReO(ReO₄)₂] was obtained. LReO₃]⁺ is deprotonated in alkaline solution (pK_a = 10.3 + 0.2, 25°C) and (C₆H₁₄N₃)ReO₃] was isolated as a yellow solid. The latter amido rhenium(VII) compound reacted in dimethylformamide with R---X (R = CH₃, benzyl; X = Cl), affording at the cyclic amine, N,N′,N″-trisalkylated complexes of the type L′ReO₃]X. The monomeric rhenium(V) complexes LReOX₂]X (X = Cl, Br, I) were obtained from the reaction of n-Butyl₄N]ReOX₄ and L in acetonitrile. IR, UV-vis, ¹⁷O NMR spectra of these compounds are reported.