Syntheses and X-ray Structures of Monocyclic, Bicyclic, and Spirocyclic Gallium and Indium Boraamidinates

The reactions of {Li2[PhB(NtBu)2]}2 with GaCl3 in various stoichiometries yield [Li(thf)4][PhB(μ-NtBu)2GaCl2·GaCl3]
(1), [PhB(μ-NtBu)2GaCl]2 (2), and {μ-Li(OEt2)[PhB(NtBu)2]Ga} (3a), a series of complexes in which the three chloride
ligands are successively replaced by the dianion [PhB(NtBu)2]2-. The X-ray structures of 1, 2, and 3a show that
the boraamidinate ligand adopts an N,N‘-chelating mode. In the ion-separated complex 1, one of the nitrogen
atoms is coordinated to a GaCl3 molecule. The related indium complexes [μ-LiCl(thf)2][PhB(μ-NtBu)2InCl]2 (4) and
{μ-Li(OEt2)[PhB(μ-NtBu)2]In} (3b) were obtained in a similar manner. Complex 4 is the indium analogue of 2 with
the incorporation of a bissolvated LiCl molecule. In 3a and 3b the spirocyclic {[PhB(μ-NtBu)2]2M}- (M = Ga, In)
anions are N,N‘-chelated to the [Li(OEt2)]+ counterion. Prolonged reactions result in the formation of [PhB(μ-NtBu)2GaCl][tBuN(H)GaCl2] (5) and {[PhB(μ-NtBu)2InCl][tBuN(H)InCl2][μ-LiCl(OEt2)2]} (6), respectively. The X-ray
structures of 5 and 6 reveal bicyclic structures which formally involve the entrapment of the monomers tBuN(H)MCl2 by a four-membered BN2M ring (M = Ga, In). The synthesis and X-ray structure of Cl2Ga[μ-N(H)tBu]2GaCl2
are also reported.