Synthesis and Characterization of the Monomeric Gallium Monoamides t-Bu₂GaN(R)SiPh₃ (R = t-Bu, 1-Adamantyl), Trip₂MN(H)Dipp (M = Al, Ga; Trip = 2,4,6-i-Pr₃C₆H₂; Dipp = 2,6-i-Pr₂C₆H₃), and Trip₂GaNPh₂

The synthesis and characterization of the monomeric, main group 3 monoamides t-Bu₂GaN(R)(SiPh₃) (R = t-Bu (1); R = 1-Adamantyl (1-Ad) (2)), Trip₂MN(H)Dipp (M = Al (3); M = Ga (4)) (Trip = 2,4,6-i-Pr₃C₆H₂, Dipp = 2,6-i-Pr₂C₆H₃), and Trip₂GaNPh₂ (5) are described. The compounds were characterized by X-ray crystallography and ¹H NMR and IR spectroscopy. The crystal structures show the molecules to be monomeric with trigonal planar metal and nitrogen coordination. The Ga-N bond lengths range from 1.847(12) Å in 4 to 1.924(2) Å in 2. The Al-N bond length observed in 3 is 1.784(3) Å. The variation may be explained mostly on the basis of different steric and electronic properties of the bulky ligands. It was concluded, on the basis of VT ¹H NMR data, that the p-p π-bonding contribution to M-Nbond strength in the aluminum or gallium species is <10 kcal mol⁻¹. Crystal data at 130 K, with Mo Kα (λ = 0.71069 Å) radiation, are as follows: t-Bu₂GaN(t-Bu)SiPh₃ (1), a = 14.795(6) Å, b = 9.807(6) Å, c = 19.657(9) Å, β = 99.39(4)°, V = 2824(1) ų, space group P2₁/c, Z = 4, 2361 (I > 2σ(I)) data, R = 0.053; t-Bu₂GaN(l-Ad)SiPh₃ (2), a = 10.191(3) Å, b = 10.740(3) Å, c = 15.467(5) Å, α = 69.82(2)°, β = 82.79(2)°, γ = 82.75(2)°, V = 1568.4(8) ų, space group P1̅, Z = 2, 5130 (I > 3σ (I)) data, R = 0.037; Trip₂AlN(H)Dipp (3), a = 11.643(5) Å, b = 18.460(6) Å, c = 37.165(14) Å, β = 95.86(3)°, V= 7947(5) ų, space group C2/c, Z = 8, 3639 (I > 2σ(I)) data, R = 0.056; Trip₂GaN(H)Dipp (4), a = 11.588(8) Å, b = 18.496(14) Å, c = 37.27(2) Å,β = 95.17°, V = 7956(9) ų, space group C2/c, Z = 8, 1837 (I > 2σ(I)) data, R = 0.084; Trip₂GaNPh₂ (5), a = 12.732(4) Å, b = 15.656(5) Å, c = 18.462(6) Å, V = 3680(2) ų, space group Pccn, Z = 4, 1944 (I > 2σ(I)) data, R = 0.092.