Synthesis, Characterization, and Reactivity of Aluminum Alkyl/Amide Complexes Supported by Guanidinate and Monoanionic OCO-Pincer Ligands

The synthesis and characterization of mixed alkyl/amide Al complexes supported by guanidinate and monoanionic OCO-pincer ligands are described. In situ generation of the lithium-guanidinate reagents via reaction of carbodiimides and lithium-amide reagents, followed by reaction with the corresponding AlMexCl3−x reagents, resulted in the formation of compounds 1−3. Subsequent reaction with lithium arylamide reagents provided access to mixed alkyl/amide- and bis-amide-substituted complexes 4−6, which were characterized by multinuclear NMR spectroscopy and elemental analysis. Single-crystal X-ray diffraction of compounds 5a and 6a confirmed the monomeric nature of these complexes and revealed the influence of the alkyl/amide functionalities on the bonding of the guanidinate ligands. A similar synthetic approach resulted in isolation of an OCO-pincer-supported Al dialkyl complex, which was also fully characterized. In contrast to the guanidinate compounds, complex 8 showed activity toward intramolecular hydroamination of 2,2-diphenylpent-4-en-1-amine.