Synthetic and structural studies of donor-functionalized alkoxy derivatives of gallium.

The synthesis of a range of alkyl/chloro-gallium alkoxide and amido/alkoxide compounds was achieved via a series of protonolysis and alcoholysis steps. The initial reaction involved the synthesis of Me(Cl)Ga{N(SiMe(3))(2)} (1) via methyl group transfer from the reaction of GaCl(3) with two equivalents of LiN(SiMe(3))(2). Reaction of 1 with varying amounts of ROH resulted in the formation of Me(Cl)Ga(OR) (2, R = CH(2)CH(2)OMe; 3, CH(CH(3))CH(2)NMe(2)), [Me(Cl)Ga{N(SiMe(3))(2)}(μ(2)-OR)Ga(Cl)Me] (4, R = CH(2)CH(2)NMe(2)), or [MeGa(OR)(2)] (5, R = CH(CH(3))CH(2)NMe(2)). Compound 4 represents an intermediate in the formation of dimeric complexes, of the type Me(Cl)Ga(OR), when formed from compound Me(Cl)Ga{N(SiMe(3))(2)}. A methylgallium amido/alkoxide complex MeGa{N(SiMe(3))(2)}(OCH(2)CH(2)OMe) (6) was isolated when 2 was further reacted with LiN(SiMe(3))(2). In addition, reaction of 2 with HO(t)Bu resulted in a simple alcohol/alkoxide exchange and formation of Me(Cl)Ga(O(t)Bu) (7). In contrast to the formation of 1, the in situ reaction of GaCl(3) with one equivalent of LiN(SiMe(3))(2) yielded Cl(2)Ga{N(SiMe(3))(2)} in low yield, where no methyl group transfer has occurred. Reaction of alcohol with Cl(2)Ga{N(SiMe(3))(2)} was then found to yield Cl(2)Ga(OR) (8, R = CH(2)CH(2)NMe(2)), and further reaction of 8 with LiN(SiMe(3))(2) yielded the gallium amido alkoxide complex, ClGa{N(SiMe(3))(2)}(OR) (9, R = CH(2)CH(2)NMe(2)), similar to 6. The structures of compounds 4, 5, 7, and 8 have been determined by single-crystal X-ray diffraction.