Redox non-innocent bis-silylene aluminium complexes with a carborane backbone

Abstract

The redox non-innocent bis-silylenyl ortho-carborane ligands [Si^II(CC_cage)Si^II] (CC_cage = o-C₂B₁₀H₁₀, Si^II = ArC(N^tBu)₂Si; Ar = C₆H₅, p-^tBuC₆H₄), with their particular chelating and electronic properties, have been employed for the synthesis of new donor-stabilized Si^II → Al^III complexes, potential precursors to low oxidation state aluminium complexes. Due to the redox non-innocence of the carborane backbone, [AlI₂⁺] complexes with three ligand oxidation states were characterized: with neutral and radical anionic closo- as well as dianionic nido-C₂B₁₀ cores. Reduction at the aluminium center could also be enacted with potassium/naphthalene leading to {K[Si^II(CC_cage)Si^II]Al(C₁₀H₈)} derivatives from [1 + 4] cycloaddition reaction. The mechanism of this dearomatization reaction is proposed to occur via the formation of transient low oxidation state aluminium intermediates (radicals and/or aluminylenes) that are trapped by naphthalene.