Research news, Oct. 28th, 2015
Lithium Aluminate Complexes and Alumoles from 1,4-Dilithio-1,3-Butadienes and AlEt2Cl
Yongliang Zhang, Junnian Wei, Wen-Xiong Zhang, and Zhenfeng Xi*
Inorg. Chem. 2015, DOI: 10.1021/acs.inorgchem.5b01551
Aluminum ate complexes and alumoles (aluminacyclopentadienes) are synthetically useful and structurally interesting. However, due to their variable coordination modes and complicated structures, their synthesis and structural characterization are challenging.
In this work, a series of lithium aluminate complexes and alumoles were synthesized from 1,4-dilithio-1,3-butadienes 1 (dilithio reagents) 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 Csp2 atoms and two ethyl Csp3 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 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 equivalent of AlEt2Cl. Preliminary reaction chemistry and synthetic applications of the lithium aluminate complex were also investigated.