ISOLATION OF UNUSUAL CONFORMATIONS OF THE [14]ANEN4 AZA CROWN-ETHER - SYNTHESES AND MOLECULAR-STRUCTURES OF [M(CH3)3]2[14]ANEN4 (M = AL, GA) AND THE GROUP-13 HETEROBIMETALLIC COMPLEX [AL(CH3)]2[14]ANEN4[GA(CH3)3]2

Reaction of M(CH3)3 (M = Al, Ga) with the aza crown ether [14]aneN4 affords crystalline complexes of the type [M-(CH3)3]2[14]aneN4. The alumimum compound (1) crystallizes in the monoclinic space group C2/c (No. 15) with unit cell parameters a = 21.772 (4) angstrom, b = 8.186 (2) angstrom, c = 14.274 (4) angstrom, beta = 116.63 (2)-degrees, V = 2274 angstrom, and rho-calcd = 1.01 g/cm3 for Z = 4. I is situated about a crystallographic 2-fold axis passing through the center of the aza crown. Least-squares refinement based on 1016 observed reflections with intensities I > 3-sigma-(I) in the range 3.50-degrees greater-than-or-equal-to 2-theta greater-than-or-equal-to 45.0-degrees for I converged at R = 0.039, R(w) = 0.049. The gallium compound (II), isostructural with I, crystallizes in the monoclinic space group C2/c (No. 15) with unit cell parameters a = 21.823 (8) angstrom, b = 8.189 (1) angstrom, c = 14.188 (2) angstrom, beta = 116.95 (6)-degrees, V = 2260 angstrom-3, and rho-calcd = 1.26 g/cm3 for Z = 4. Least-squares refinement based on 1570 observed reflections in the range 4.00-degrees greater-than-or-equal-to 2-theta greater-than-or-equal-to 50.0-degrees for II converged at R = 0.056, R(w) = 0.060. The [14]aneN4 aza crown assumed an unusual inverted basket conformation in I and II. Both I and II appear to be strained, as the two M(CH3)3 units and all four N-H units reside on the same side of the aza crown. The independent Al-N bond distance is 2.028 (3) angstrom, while the Ga-N bond distance is 2.124 (4) angstrom. Room-temperature reaction of I with 2 mol of trimethylgallium affords the heterobimetallic condensation compound [Al(CH3)]2[14]aneN4[Ga(CH3)3]2 (III). III crystallizes in the monoclinic space group P2(1)/n (No. 14) with unit cell parameters a = 8.195 (2) angstrom, b = 13.783 (4) angstrom, c = 11.162 (3) angstrom, beta = 90.70 (2)-degrees, V = 1261 angstrom-3, and rho-calcd = 1.34 g/cm3 for Z = 2. Least-squares refinement based on 1710 observed reflections with intensities I > 3-sigma-(I) in the range 3.50-degrees greater-than-or-equal-to 2-theta greater-than-or-equal-to 50.0-degrees converged at R = 0.036, R(w) = 0.049. III resides about a crystallographic center of symmetry with a planar Al2N2 ring occupying the central cavity of the aza crown.