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)3Cl(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)3Cl(L)]n redox series (n=+, 0, −).