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

The reactions of {Li2[PhB(Ntu)2)}2 with GaCI3 in various stoichiometries yield [Li(thf)4][PhB(mu-NtBu)2GaCl2-GaCl3] (1), [PhB(mu-NtBu)2GaCI]2 (2), and {mu-Li(OEt2)[PhB(NtBu)2]Ga} (3a), a series of complexes in which the three chloride ligands are successively replaced by the dianion [PhB(NBu)2]2. The X-ray structures of 1, 2, and 3a show that the boraamidinate ligand adopts an N,Nʹ-chelating mode. In the ion-separated complex 1, one of the nitrogen atoms is coordinated to a GaCI3 molecule. The related indium complexes mu-LiCI(thf)2][PhB(,u-NtBu)2lnCI]2 (4) and {mu-Li(OEt2)[PhB(mu-NtBu)2]ln} (3b) were obtained in a similar manner. Complex 4 is the indium analogue of 2 with the incorporation of a bissolvated LiCI molecule. In 3a and 3b the spirocyclic {[PhB(mu-NtBu)2)2M}- (M = Ga, In) anions are N,Nʹ-chelated to the [Li(OEt2)+ counterion. Prolonged reactions result in the formation of [PhB(muNtBu)2GaCI][tBuN(H)GaCl2] (5) and {[PhB(mu-Bu)2lnCI][tBuN(H)lnCl2][mu-LiCI(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[mu-N(H)tBu]2GaCl2 are also reported.