Synthesis, crystal and molecular structure of a stable monomeric five-co-ordinate gallium-amine complex, chloro(dimethyl)-1, 10-phenanthrolinegallium(III)

X-Ray single-crystal analysis, ^lH n.m.r., and molecular-weight measurements establish that the title compound has a trigonal bipyramidal structure in the solid state and in chloroform, but ionizes in water. Crystals are monoclinic, space group P21/c, with cell dimensions a = 10.75(1), b = 11.91(1), c = 15.59(1) Å, β = 134.8(1)°, Z= 4. The crystal structure was solved by the heavy-atom method and atomic parameters refined by full-matrix least-squares calculations to R 0.052 for 1 228 statistically significant reflections from diffractometer measurements. Two methyl groups [Ga-C 1.956(10) and 1.952(10) Å] and a 1, 10-phenanthroline (phen) nitrogen atom [Ga-N 2.119(6) Å] define the basal plane of the trigonal bipyramid; axial sites are occupied by the second nitrogen of the bidentate phen ligand [Ga-N 2.433(6) Å] and the chlorine atom [Ga-Cl 2.440(3) Å]. Comparison of these dimensionswith those in other gallium complexes indicates that only the Ga-N distances are significantly lengthened due to intramolecular ligand-ligand steric interactions. In addition, ¹H n.m.r. spectral studies establish the cis-configuration of the octahedral complexes cis-[GaCl2(phen)2]X (X = Cl, GaCl4, or MeGaCl3).

Duke Scholars

Author Andrew T. McPhail Chemistry