Structure and magnetism of cubic low-spin 4d5[RuIII(NH3)6]Br[SO4]

Abstract

The structure of [Ru(NH₃)₆]Br[SO₄] is reported at ca. 295 K. The space group is cubic Fmm with the ruthenium atom lying at a site of O_h symmetry. There is considerable disorder, particularly involving the sulfate ion, and this implies substantial rotational–translational coupling. The Ru–N bond length is 210.7(7) and the N–H length 100(3) pm. The magnetic susceptibility is reported from 4.5 to 300 K. The ESR spectrum between 105 and 300 K showed a g value of 1.926(5). A simple molecular-orbital model involving the π-covalence parameter k_π,π, spin-orbit coupling for the ruthenium(III) atom and small magnetic exchange completely accounted for the susceptibility and ESR spectroscopic experiments. However, the reduction of k_π,π from unity to 0.94 should be attributed to sources other than π covalence, given further theoretical and experimental evidence.