Lithium Aluminate Complexes and Alumoles from 1,4-Dilithio-1,3-Butadienes and AlEt2Cl

Article abstract of DOI:10.1021/acs.inorgchem.5b01551

A series of lithium aluminate complexes and alumoles were synthesized from 1,4-dilithio-1,3-butadienes 1 and AlEt₂Cl. Their structures were characterized using single-crystal X-ray structural analysis and NMR spectroscopy. The structure of the lithium aluminate complex 2-TMEDA showed that the Al atom adopted a tetra-coordinated mode bonded with two butadienyl C_sp2 atoms and two ethyl C_sp3 atoms. The lithium cation was located above the alumole ring. The structure of 3a revealed a dimeric 1-ethylalumole in the solid state. Diffusion ordered spectroscopy NMR spectra showed that 3a was also a dimer in C₆D₆ solvent. However, in tetrahydrofuran (THF) solution, the dimeric 3a dissociated into the 1-ethylalumole-THF adduct. The lithium aluminate complex 2 transformed into 3a-THF when treated with 1.0 equiv of AlEt₂Cl. Preliminary reaction chemistry and synthetic applications of the lithium aluminate complex were also investigated.