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 H-1 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) angstrom in 4 to 1.924(2) angstrom in 2. The Al-N bond length observed in 3 is 1.784(3) angstrom. 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 H-1 NMR data, that the p-p pi-bonding contribution to M-Nbond strength in the aluminum or gallium species is <10 kcal mol-1. Crystal data at 130 K, with Mo K(alpha) (lambda = 0.71069 angstrom) radiation, are as follows: t-Bu2GaN(t-Bu)SiPh3 (1), a = 14.795(6) angstrom, b = 9.807(6) angstrom, c = 19.657(9) angstrom, beta = 99.39(4)degrees, V = 2824(1) angstrom3, space group P2(1)/c, Z = 4,2361 (I > 2sigma(I)) data, R = 0.053; t-Bu2GaN(1-Ad)SiPh3 (2), a = 10.191(3) angstrom, b = 10.740(3) angstrom, c = 15.467(5) angstrom, alpha = 69.82(2)degrees, beta = 82.79(2)degrees, gamma = 82.75(2)degrees, V = 1568.4(8) angstrom3, space group P1BAR, Z = 2, 5130 (I > 3sigma (I)) data, R = 0.037; Trip2AlN(H)Dipp (3), a = 11.643(5) angstrom, b = 18.460(6) angstrom, c = 37.165(14) angstrom, beta = 95.86(3)degrees, V = 7947(5) angstrom3, space group C2/c, Z = 8, 3639 (I > 2sigma(I)) data, R = 0.056; Trip2GaN(H)Dipp (4), a = 11.588(8) angstrom, b = 18.496(14) angstrom, c = 37.27(2) angstrom, beta = 95.17-degrees, V = 7956(9) angstrom3, space group C2/c, Z = 8, 1837 (I > 2sigma(I)) data, R = 0.084; Trip2GaNPh2 (5), a = 12.732(4) angstrom, b = 15.656(5) angstrom, c = 18.462(6) angstrom, V = 3680(2) angstrom3, space group Pccn, Z = 4, 1944 (I > 2sigma(I)) data, R = 0.092.
