The BIAN ligand 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene: An electron sponge or a “normal” α-diimine ligand?

Abstract The compounds [ fac -Re(CO) 3 Cl(L)] and [M(CO) 4 (L)], M = Cr, Mo, W and L = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene, have been studied electrochemically and spectroelectrochemically (IR, UV–vis-NIR, EPR). The neutral rhenium complex contains an isopropyl-shielded chloride ligand; its reversible oxidation was shown to involve a largely metal-based HOMO. One electron could be added reversibly to the diimine-based LUMO of all complexes, as evident from EPR spectroscopy. However, there was no evidence for the reversible acquisition of more than one electron by L in these complexes, ruling out an electron reservoir functionality with multielectron reactivity. DFT and TD-DFT calculations were performed for the [Re(CO) 3 Cl(L)] n redox series (n = +, 0, −).