Preparation and characterization of mixed alkyl amido complexes of gallium

A series of primary amido gallium alkyl complexes that includes a base free dimer, [(t)Bu(2)Ga(mu-N(H)(t)Bu)](2) (1), Lewis base stabilized monomeric complexes, (n)Bu(2)Ga(N(H)(t)Bu)(THF) (2) and (n)Bu(2)Ga[NH(2,6-Me(2)C(6)H(3))]py (3) and an anionic complex, (n)Bu(2)Ga[NH(2,6-Me(2)C(6)H(3))](2)[Li(Et(2)O)] (4) is reported. Complex 1 crystallizes in the triclinic space group P-1 (a = 10.265(5) Angstrom, b = 15.752(6) Angstrom, c = 8.932(4) Angstrom, alpha = 90.32(3)degrees, beta = 105.61(3)degrees, gamma = 88.24(4)degrees) with two molecules, each residing on an inversion center, in the asymmetric unit. Structural analysis revealed a planar Ga2N2 core with both the bridging N and the Ga centers in distorted tetrahedral environments (Ga-C distances 2.052(3)-2.065(3) Angstrom and Ga-N distances 2.060(3)-2.069(3) Angstrom). The use of excess amido ligand allowed the isolation and crystallization of 4. Complex 4 crystallized in the monoclinic space group P2(1)/n (a = 8.666(2) Angstrom, b = 22.305(3) Angstrom, c = 15.570(3) Angstrom, beta = 103.47(2)) with Z = 4. The pseudotetrahedral gallium center has a coordination sphere composed of two amido ligands (Ga-N1 = 2.011(8) Angstrom, Ga-N2 = 2.006(7) Angstrom), and two (n)Bu ligands (Ga-C17 = 2.002(9) Angstrom, Ga-C21 = 1.985(12) Angstrom). A bridging interaction of the lithium cation with the lone pair of electrons on each of amido nitrogen atoms generates a molecular core which is made up of a planar Ga-N1-Li-N2 distorted square (N1-Ga1-N2 94.4 degrees, Ga1-N2-Li1 86.2 degrees, N1-Li1-N2 92.2 degrees, Ga1-N1-Li1 87.1 degrees).