Hydride Abstraction from a BH₄– Anion in a Carbazolyl Lanthanum Boranate

Lanthanum borohydride complexes were synthesized by introducing a sterically demanding carbazole ligand (dtbpCbz = 1,8-bis(3,5-di-tert-butylphenyl)-3,6-di-tert-butylcarbazolyl) into the coordination sphere of the lanthanide. Compound 1 (dtbpCbzLa(η3-BH4)2(THF)2) was obtained by a straightforward borohydride metathesis approach. We further investigated the coordination behavior toward abstraction of the solvent molecules. Removal of one THF molecule results in the dimeric structure of complex 2 ([dtbpCbzLa(BH4)2(THF)]2). However, the reaction with tris(pentafluorophenyl)borane does not lead to a second abstraction of THF. Instead, we observed borohydride decomposition and the formation of a π-coordinated lanthanum carbazolyl complex, (dtbpCbzBH3)La(BH4)[HB(C6F5)3](THF) (3).