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

Abstract

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).