Complexes of vanadium(II) and (III) are relatively exchange inert and reducing.
Those of V(IV) and V(V) are oxidants.
Vanadium ion is rather large and some complexes achieve coordination numbers greater than 6, as is the case in [V(CN)₇]⁴⁻. Oxovanadium(V) also forms 7 coordinate coordination complexes with tetradentate ligands and peroxides and these complexes are used for oxidative brominations and thioether oxidations.
The coordination chemistry of V⁴⁺ is dominated by the vanadyl center, VO²⁺, which binds four other ligands strongly and one weakly (the one trans to the vanadyl center).
An example is vanadyl acetylacetonate (V(O)(O₂C₅H₇)₂).
In this complex, the vanadium is 5-coordinate, square pyramidal, meaning that a sixth ligand, such as pyridine, may be attached, though the association constant of this process is small.
Many 5-coordinate vanadyl complexes have a trigonal bipyramidal geometry, such as VOCl₂(NMe₃)₂. The coordination chemistry of V⁵⁺ is dominated by the relatively stable dioxovanadium coordination complexes which are often formed by aerial oxidation of the vanadium(IV) precursors indicating the stability of the +5 oxidation state and ease of interconversion between the +4 and +5 states.
Complexes of vanadium(II) and (III) are relatively exchange inert and reducing. Those of V(IV) and V(V) are oxidants. Vanadium ion is rather large and some complexes achieve coordination numbers greater than 6, as is the case in [V(CN)₇]⁴⁻. Oxovanadium(V) also forms 7 coordinate coordination complexes with tetradentate ligands and peroxides and these complexes are used for oxidative brominations and thioether oxidations. The coordination chemistry of V⁴⁺ is dominated by the vanadyl center, VO²⁺, which binds four other ligands strongly and one weakly (the one trans to the vanadyl center). An example is vanadyl acetylacetonate (V(O)(O₂C₅H₇)₂). In this complex, the vanadium is 5-coordinate, square pyramidal, meaning that a sixth ligand, such as pyridine, may be attached, though the association constant of this process is small. Many 5-coordinate vanadyl complexes have a trigonal bipyramidal geometry, such as VOCl₂(NMe₃)₂. The coordination chemistry of V⁵⁺ is dominated by the relatively stable dioxovanadium coordination complexes which are often formed by aerial oxidation of the vanadium(IV) precursors indicating the stability of the +5 oxidation state and ease of interconversion between the +4 and +5 states.
Vanadium