Arylazoimidazole compounds of rhenium nitrosyl: Synthesis, spectral characterization and reactivity

Abstract

Reductive nitrosylation of ReO 4 - in aqueous alkaline medium by NH 2OH · HCl furnishes the Re(NO) 3+ moiety which reacts with arylazoimidazoles to give hitherto unknown arylazoimidazole (RaaiR′) complexes of rhenium nitrosyl, [Re(NO)(OH) 3(RaaiR′)]. The complexes are non-electrolytes in CH 3CN. They exhibit υ(NO) at ca. 1700 cm −1 and are magnetically active. The ESR profiles in the polycrystalline state at 298 K show 〈 g av〉 ≈ 2.0. A spin forbidden ESR transition (Δ M s = 2, g ∼ 4) is observed at <1600 Gauss. A well defined sextet due to the metal hyperfine structure is observed. The complexes exhibit a moderately intense visible band at 440–450 nm which may be ascribed to a metal-to-ligand charge transfer transition, along with intraligand charge transfer, π → π∗ and n → π∗, transitions at <400 nm. Cyclic voltammetry exhibits quasireversible to irreversible metal oxidation and ligand reductions. The reaction of [Re(NO)(OH) 3(RaaiR′)] with camphor in alkaline medium has assisted C–N bond fusion by synthesizing a camphorquinone monoxime complex.