An Aluminum Telluride with a Terminal Al=Te Bond and its Conversion to an Aluminum Tellurocarbonate by CO₂ Reduction

Facile access to dimeric heavier aluminum chalcogenides [(NHC)Al(Tipp)-μ-Ch]₂ (NHC=IiPr (1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene, IMe₄ (1,3,4,5-tetramethylimidazol-2-ylidene); Tipp=2,4,6-iPr₃C₆H₂; Ch=Se, Te) by treatment of NHC-stabilized aluminum dihydrides with elemental Se and Te is reported. The higher affinity of IMe₄ in comparison with IiPr toward the Al center in [(NHC)Al(Tipp)-μ-Ch]₂ can be used for ligand exchange. Additionally, the presence of excess IMe₄ allows for cleavage of the dimers to form a rare example of a neutral multiply bonded heavier aluminum chalcogenide in the form of a tetracoordinate aluminum complex, (IMe₄)₂(Tipp)Al=Te. This species reacts with three equivalents of CO₂ across two Al−C^NHC and the Al=Te bond affording a pentacoordinate aluminum complex containing a dianionic tellurocarbonate ligand [CO₂Te]²⁻, which is the first example of tellurium analogue of a carbonate [CO₃]²⁻.