Crystal and Molecular Structure of Tris(Ethane-1,2-Diamine)Osmium(III) Trifluoromethanesulfonate Monohydrate

Abstract

The crystal and molecular structure of racemic [Os(en)₃] (CF₃SO₃)₃.H₂O has been determined. The [Os(en)₃]³⁺ ion adopts a le ξob configuration and has approximate C₂ symmetry with an Os-N(av.) bond length of 2.11 Å and a bite angle for the chelate of - 82º. The previously recorded structure of the [Os(en-H)₂(en)]²⁺ ion in which two deprotonated ethane-1,2-diamine ligands adoptoa cis configuration of the two amido donors, and in which the Os^IV -N( amido ) bonds (1.90 Å) are much shorter than the Os-N(amine) bonds, 2.11 ( cis ), 2.19 (trans), along with the present structure indicates a bond order > 1 for the osmiumo amido bond. The normal Os-N bond lengths fall into well defined ranges OS-NR₃ (2.11-2.14 Å), Os=NR₂- (~1.90 Å),Os=NR₂ (- 1.70 Å) and Os=N^3-(- 1.58-1.63 Å). These single bond lengths are more affected by trans effects than the formal oxidation state of the osmium centre.