Synthesis, structure, and properties of trichloro- and tribromo-(2,9-dimethyl-1,10-phenanthroline)gold(III)

Abstract

The title complexes [(4) Au(dmp)Cl₃ and (5) Au(dmp)Br₃, dmp = 2,9-dimethyl-1,10-phenanthroline] have been synthesised and their crystal and molecular structures determined from three-dimensional X-ray data obtained by counter methods. Crystals of (4) and (5) are not isomorphous though both are monoclinic, space group P2₁/C, with Z= 4 in unit cells of dimensions: (4)a= 7.343(1), b= 18.712(3), c= 12.143(3)Å, β= 112.29(2)°;(5), a= 8.046(1), b= 10.478(3), c= 20.079(5)Å, β= 92.65(2)°. The structures were solved by the heavy-atom method and refined by full-matrix least-squares to R 0.035 [(4) 904 reflections] and 0.060 [(5) 1122 reflections].

The compounds consist of discrete, diamagnetic five-co-ordinate molecules in both the solid state and in solution in aprotic solvents. The distribution of the ligands about the metal is approximately square pyramidal with the axial ligand displaced from the vertical, and at a relatively great distance from the metal, so that they may also be described as strongly distorted square planar. The direction of the distortion is such as to reduce the energy of the high-spin (triplet) state, but the magnitude is too low to produce a high-spin ground-state.