Research news, Sep. 27th, 2017

 Formation and Ligand-Based Reductive Chemistry of Bridged Bis-alkylidene Scandium(III) Complexes

Wangyang Ma, Chao Yu, Yue Chi, Tianyang Chen, Lianjun Wang, Jianhao Yin,

Baosheng Wei, Ling Xu, Wen-Xiong Zhang,* and Zhenfeng Xi

Chem. Sci. 2017, 8, 6852-6856.

The chemistry of rare-earth carbene and alkylidene complexes including their synthesis, structure and reaction is a challenging issue because of their high reactivity (or instability) and the lack of synthetic methods. In this work, we will report the first synthesis of the bridged bis-alkylidene complexes which feature a 2-butene-1,1,4,4-tetraanion and four Sc−C(sp3) bonds by the reaction of 1,4-dilithio-1,3-butadienes with ScCl3. This reaction proceeds via two key intermediates: an isolable scandacyclopentadiene and a proposed scandacyclopropene. The scandacyclopentadiene undergoes β,β′-C−C bond cleavage to generate the scandacyclopropene, which then dimerizes to afford the bridged bis-alkylidene complex via a cooperative double metathesis reaction. Reaction chemistry study of the bridged bis-alkylidene complex reveals their ligand-based reductivity towards different oxidants such as hexachloroethane, disulfide and cyclooctatetraene.