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

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.