Oligomeric rods of alkyl- and hydridogallium imides.

Reaction of [RGa(NMe(2))(2)](2), where R = Me, Et, Bu, and Hx, with ammonia at 150 degrees C in an autoclave produced insoluble white powders formulated as oligomers of [RGaNH](n). The analogous reaction between NH(3) and MeGa[N(SiMe(3))(2)](2) at low temperature (<25 degrees C) formed an isolable intermediate, [MeGa(mu-NH(2))N(SiMe(3))(2)](2), that was characterized using single-crystal X-ray diffraction. Infrared spectroscopy and X-ray diffraction of the oligomers were consistent with a rodlike structure comprised of six-membered, [RGaNH](3) rings stacked perpendicular to the long axis of the rod. The method of synthesis, formula, and diffraction results suggested a structural similarity between the alkyl, [RGaNH](n)(), and the previously reported hydride, [HGaNH](n). The structural and electronic properties of rods having the general formula H(3)[(HXYH)(3)](n)H(3) (XY = GaN, GeC; n = 1-9) were investigated using density functional theory. Atomic electronegativity differences between the group 13/15 and 14/14 systems were found to play important roles in the geometrical structures of the two rods and also caused significant differences in the electronic structures. Energetically, it was found to be increasingly favorable to add additional cyclotrigallazane rings to the GaN rods, while for the GeC rods, there was a roughly constant energy cost associated with each additional ring. The electric dipole moments of the GaN rods increased substantially with length; in the GeC rods, charge separation occurred to a much smaller extent and had a polarization opposite to that found in GaN. In addition, increased dipole moments correlated with smaller electronic excitation energies, as predicted by time-dependent density functional theory. All of the powders exhibited luminescence in the visible spectrum at room temperature. Structure observed in the photoluminescence spectra of [HGaNH](n) and [MeGaNH](n) was interpreted as arising from rods of different length.

Base Effects on the Formation of Four- and Five-Coordinate Cationic Aluminum Complexes.

This work was conducted as part of our continuing effort to determine the factors that affect cation formation for organometallic aluminum complexes. In this study, the interactions of R(2)AlX (where R = Me, (i)Bu, (t)Bu; X = Cl, Br, I) with the monodentate bases thf, pyridine, NEt(3), HN(i)Pr(2), H(2)N(i)Bu, H(2)N(t)Bu, and O=PPh(3) are examined to determine the role of the base in cation formation. These reactions resulted in the neutral adducts of the general form R(2)AlX.base (1-6, 8, 10, and 12) as well as the cationic complexes [R(2)Al(base)(2)]X (7, 9, and 11). The reactions of Me(2)AlX (where X = Cl, Br) with PMDETA (N,N',N",N"'-pentamethyldiethylenetriamine) and the catalytic activity of the resulting cationic complexes (13 and 14) are also discussed. All of the compounds were characterized by mp, IR, (1)H-NMR, and elemental analyses, and in one an X-ray crystallographic study was carried out. X-ray data for 13: triclinic, P&onemacr;, a = 6.9542(6) Å, b = 12.2058(10) Å, c = 13.2417(11) Å, alpha = 106.236(2) degrees, beta = 98.885(2) degrees, gamma = 93.807(2) degrees, V = 1059.06(15) Å(3), and Z = 2 for 181 parameters refined on 4358 reflections having F > 6.0sigma(F), R = 0.0697, and R(w) = 0.0697.

A New Class of Aluminum Cations Based upon Tetradentate (N(2)O(2)) Chelating Ligands.

Herein are described the synthesis and characterization of the complexes of formula LAlR (where R = Cl and L = Salen (1), SalenCl (2), Acen (3) and where R = Me and L = Salen (4), SalenCl (5), Acen (6); Salen = N,N'-ethylenebis((2-hydroxyphenyl)methylimine), SalenCl = N,N'-ethylenebis((2-hydroxy-5-chlorophenyl)methylimine), Acen = N,N'-ethylenebis((2-hydroxyphenyl)-1-ethylimine)). The LAlCl derivatives dissolve in water and MeOH to yield the cationic complexes [LAl(H(2)O)(2)](+)Cl(-) (L = Salen (7), SalenCl (8), Acen (9)) and [LAl(MeOH)(2)](+)Cl(-) (L = Salen (10), SalenCl (11), Acen (12)), respectively. An alternative preparation of the cationic species involves the reaction of the LAlCl derivative with NaBPh(4). This leads to complexes of formula [LAl(MeOH)(2)](+)BPh(4)(-) (L = Salen (13), SalenCl (14), Acen (15)). Complexes 4-6 can be reacted with either MeOH or 4-chloro-3,5-dimethylphenol (Ph') to form complexes of general formula LAlOR (R = Me, L = Salen (16), SalenCl (17), Acen (18); R = Ph', L = Salen (19), SalenCl (20), Acen (21)). All of the compounds were characterized by IR, melting points, elemental analyses, and, when soluble, NMR. Additionally, the crystal structures of 7, 13, 15, and 18 were obtained.