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-iPr₃ C₆ H₂ ; 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 [CO₂ Te]^2- , which is the first example of tellurium analogue of a carbonate [CO₃ ]^2- .

Mesoionic Dithiolates (MIDts) Derived from 1,3-Imidazole-Based Anionic Dicarbenes (ADCs)

Mesoionic dithiolates [(MIDtAr )Li(LiBr)2 (THF)3 ] (MIDtAr ={SC(NDipp)}2 CAr; Dipp=2,6-iPr2 C6 H3 ; Ar=Ph 3 a, 3-MeC6 H4 (3-Tol) 3 b, 4-Me2 NC6 H4 (DMP) 3 c) and [(MIDtPh )Li(THF)2 ] (4) are readily accessible (in≥90 % yields) as crystalline solids on treatments of anionic dicarbenes Li(ADCAr ) (2 a-c) (ADCAr ={C(NDipp)2 }2 CAr) with elemental sulfur. 3 a-c and 4 are monoanionic ditopic ligands with both the sulfur atoms formally negatively charged, while the 1,3-imidazole unit bears a formal positive charge. Treatment of 4 with (L)GeCl2 (L=1,4-dioxane) affords the germylene (MIDtPh )GeCl (5) featuring a three-coordinated Ge atom. 5 reacts with (L)GeCl2 to give the Ge-Ge catenation product (MIDtPh )GeGeCl3 (6). KC8 reduction of 5 yields the homoleptic germylene (MIDtPh )2 Ge (7). Compounds 3 a-c and 4-7 have been characterized by spectroscopic studies and single-crystal X-ray diffraction. The electronic structures of 4-7 have been analyzed by DFT calculations.

Chalcogen complexes of anionic N-heterocyclic carbenes

Chalcogen complexes of anionic N-heterocyclic carbenes were isolated as lithium salts and their protonation and oxidation were studied.