Bis‐Silylene‐Supported Aluminium Atoms with Aluminylene and Alane Character

The suitability of electron‐rich bis‐silylenes, specifically the neutral chelating [Si II (Xant)Si II ] ligand (Si II =PhC(N t Bu) 2 Si, Xant=9,9‐dimethylxanthene) and the anionic [Si II (N Acrid )Si II )] − pincer ligand (N Acrid =2,7,9,9‐tetramethylacridane), has been successfully probed to stabilize monovalent bis‐silylene‐supported aluminium complexes (aluminylenes). At first, the unprecedented aluminium(III) iodide precursors [Si II (Xant)Si II ]AlI 2 + I − 1 and [Si II (N Acrid )Si II )]AlI 2 2 were synthesized using AlI 3 and [Si II (Xant)Si II ] or [Si II (N Acrid )Si II )]Li(OEt 2 )], respectively, and structurally characterized. While reduction of 1 with KC 8 led merely to unidentified products, the dehalogenation of 2 afforded the dimer of the desired {[Si II (N Acrid )Si II )]Al:} aluminylene with a four‐membered Si IV 2 Al III 2 ring. Remarkably, the proposed aluminylene intermediates [Si II (Xant)Si II ]Al I I and {[Si II (N Acrid )Si II )]Al:} could be produced through reaction of 1 and 2 with Collman's reagent, K 2 Fe(CO) 4 , and trapped as Al I :→Fe(CO) 4 complexes 5 and 6 , respectively. While 6 is stable in solution, 5 loses one CO ligand in solution to afford the silylene‐ and aluminylene‐coordinated iron(0) complex 7 from an intramolecular substitution reaction. The electronic structures of the novel compounds were investigated by Density Functional Theory calculations.