Reactivity of Aluminum Complexes of Redox-Active Ligand toward N-Heterocyclic Carbene and Its Thione

The reaction of dialane (dpp-Bian)Al–Al(dpp-Bian) (1) (dpp-Bian is dianion of 1,2-bis[(2,6-diisopropylphenyl)imino]-acenaphthene) with 1 mol equiv of 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (iPr2ImMe) results in the Al-carbene adduct (dpp-Bian)(iPr2ImMe)Al–Al(dpp-Bian) (3). In the course of the reaction of dialane 1 with 2 mol equiv of 1,3-diisopropyl-4,5-dimethylimidazol-2-thione (iPr2ImtMe) a half of the thione amount undergoes a cleavage of sulfur–carbon double bond. In the product (dpp-Bian)(iPr2ImMe)Al(μ-S)Al(iPr2ImtMe)(dpp-Bian) (4) aluminum atoms coordinate carbene as well as thione ligands. Compound 4 is thermally robust: no reduction of C═S bond in thione moiety by the dpp-Bian ligands could be observed in toluene for 24 h at 100 °C. Complex {(dpp-Bian)(iPr2ImMe)Al}2(μ-S) (5) was isolated from the reaction of dialane 1, iPr2ImMe, and iPr2ImtMe (1:1:1). The reaction of mononuclear (dpp-Bian)AlH(THF) (2) (THF = tetrahydrofuran) affords compound (dpp-Bian)AlH(iPr2ImMe) (6). Compounds 3–6 were...