Reactivity of boryllithium with AlMe3, AlEt3, and GaMe3, including the synthesis of a lanthanum heterogallate complex

Abstract

Treatment of boryllithium (THF)₂Li[B(NDippCH)₂] (Dipp = 2,6-diisopropylphenyl) with various amounts of AlMe₃ or GaMe₃ leads to the formation of inter group 13 compounds. Equimolar reactions result in ate complexes of the type (THF)_nLi(Me₃M)[B(NDippCH)₂] (M = Al, Ga) with discrete (n = 2, 3) or eight-membered ring structures (n = 1). We reported previously that use of excessive amounts of group 13 metal methyl compounds can result in four-coordinate THF-adducts (THF)(Me₂M)[B(NDippCH)₂] or unsolvated complexes {(Me₂M)[B(NDippCH)₂]}_x (M = Al, x = 2; M = Ga, x = 1) via separation of LiMMe₄. Polymeric [(THF)Li(Et₃Al){B(NDippCH)₂}]_n is formed when boryllithium is reacted with an equimolar amount of AlEt₃. The discrete THF-adduct (THF)Et₂Al[B(NDippCH)₂] can be isolated when using a boryllithium/AlEt₃ ratio of 1 : 5. The reaction of THF-adduct (THF)Me₂Ga[B(NDippCH)₂] with La(AlMe₄)₃ affords the heterogallate complex La[(Me₃Ga){B(NDippCH)₂}]₃, according to a donor-assisted tetramethylaluminate/alkylgallate exchange. The obtained complexes feature rare examples of crystallographically characterized non-cluster compounds with unsupported B–Al and B–Ga contacts.