Organoaluminum Cation Catalyzed Selective Hydrosilylation of Carbonyls, Alkenes, and Alkynes

The N,N’-chelated β-diketiminate analogue i. e., conjugated bis-guanidine (CBG) ligand L(3H) [L= {(ArHN)(ArN)−C=N−C=(NAr)(NHAr)}; Ar=2,6-Et2-C6H3], has been used to synthesize mono- and dinuclear Al(III) dimethyl complexes, [L(2H) AlMe2] (1) and [L(H)(AlMe2)2] (2). Compounds 1 and 2 are synthesized by deprotonation method using free ligand and appropriate stoichiometric amounts of AlMe3 and are structurally characterized by a single-crystal X-ray diffraction technique. Moreover, the reaction of compound 1 with B(C6F5)3 afforded a three-coordinate aluminum methyl cation [L(2H)AlMe]+ [MeB(C6F5)3]− 3 in good yield. Compound 3 was thermally stable and characterized by multinuclear NMR spectroscopy. Furthermore, we demonstrated that compound 3 catalyzed hydrosilylation of carbonyls, alkenes, and alkyne with triethylsilane (HSiEt3) under solvent-free conditions. We found that catalyst 3 is also effective for large-scale hydrosilylation reactions. Additionally, we have shown that compound 3 catalyzed benzaldehyde's intermolecular chemoselective hydrosilylation over other reducible functional groups.