High‐Pressure 17O‐NMR. Study of Vanadium (II) in Water: A Second Example of an Associative Interchange Mechanism (Ia) for Solvent Exchange on an Octahedral Divalent Transition‐Metal Ion

The water exchange of [V(H2O)6]Cl2 in aqueous solution has been studied as a function of temperature and pressure (up to 250 MPa), by measuring the 17O‐FT‐NMR. line‐widths of the free water resonance at 8.13 MHz. The kinetic parameters obtained are K = 87±4 s−1, ΔH* = +61.8 ± 0.7 kJ mo1−1 and ΔS* = −0.4±1.9 J mol−1 K−1. A pressure‐independent volume of activation ΔV* = −4.1±0.1 cm3 mol−1 is obtained, suggesting an associative interchange (Ia) mechanism for this early divalent metal ion.