Structural Features of Monomeric Octahedral d ²-Rhenium(V) Monooxo Complexes with Oxygen Atoms of Tridentate Chelating (O,P,O and O,P,N) Ligands

The structural features of eleven mononuclear octahedral d2-Re(V) monooxo complexes with tridentate chelating (O,P,O and O,P,N) ligands, [ReO$$\left( {{\text{L}}_{{{\text{tri}}}}^{m}} \right)$$$$\left( {{\text{L}}_{{{\text{bi}}}}^{n}} \right)$$], [ReO$$\left( {{\text{L}}_{{{\text{tri}}}}^{m}} \right)$$Cl2], and [ReO$$\left( {{\text{L}}_{{{\text{tri}}}}^{m}} \right)$$-Cl(PPh3)], are considered. The Re–O$${{\left( {{\text{L}}_{{{\text{tri}}}}^{m}} \right)}_{{trans}}}$$ bond lengths are commensurable (or somewhat shorter) with the Re–O$${{\left( {{\text{L}}_{{{\text{tri}}}}^{m}} \right)}_{{cis}}}$$ or Re–O(ST) bond lengths, which is indicative of the presence of pseudo-dioxo ReO2 groups with increased bond orders for both trans-arranged Re–O bonds. In the structures of two compounds, the Re–O$${{\left( {{\text{L}}_{{{\text{bi}}}}^{{\text{2}}}} \right)}_{{trans}}}$$ bonds are, on average, 0.094 Å longer than Re–O(ST) and 0.189 Å longer than Re–O$${{\left( {{\text{HL}}_{{{\text{bi}}}}^{{\text{3}}}} \right)}_{{cis}}}$$, in accordance with the structural consequences of the trans-effect of a multiply bonded oxo ligand.