Abstract
The zerovalent metal in [Mo(CO)4(bmiq)] binds the two imidazole-N-imine donors of 2,3-bis(1-methylimidazol-2-yl)quinoxaline (bmiq), resulting in a seven-membered chelate ring coordinated in cis configuration. DFT calculations confirm the preference for a seven-membered vs five-membered ring chelation alternative as well as the experimental structural parameters. The complex is reversibly reduced in CH2Cl2 at −2.08 V and reversibly oxidized at −0.14 V vs ferrocenium/ferrrocene. The facilitated oxidation to a stable cation is attributed to the donor effect from the imidazole rings. In agreement with the DFT-calculated characteristics of the HOMO and LUMO, the in situ EPR studies at a Pt electrode reveal a MoI signature for the cation (g1 = 1.967, g2 = 1.944, g3 = 1.906; Aiso(95,97 Mo) = 50 G) and a quinoxaline radical-type EPR spectrum with dominant 14N coupling (2 N) of 6.0 G for the anion. IR spectroelectrochemistry confirms these assignments, showing small (Δν ≤ 20 cm–1) low-energy shifts of carbonyl str...
Published Version
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