Structural features of monomeric octahedral d ² rhenium(V) oxo complexes with oxygen atoms in trans-positions to oxo ligands: Complexes with propoxo ligands in trans-positions to O(oxo)

Some structural features of mononuclear octahedral rhenium(V) oxo complexes with oxygen atoms of propoxo ligands O(Pr-iso)− in trans-positions to multiply bonded oxo ligands are considered. The complexes contain monodentate inorganic or organic ligands or bi- and tetradentate organic ligands in the equatorial plane. Re-O(OPr)trans bonds, as well as the other bonds with (ORalkoxo)trans alkoxo ligands (R = Me, Et), are considerably shortened, instead of being elongated, due to the structural manifestation of the trans-effect of multiply bonded oxo ligands. This is explained by that these Re-O(ORalkoxo) bonds also have an increased multiplicity; that is, d2 rhenium(V) monooxomonoalkoxo complexes should be considered as pseudo-dioxo Re(=O)(=ORalkoxo) compounds.