High-pressure NMR kinetics. Part 10. Volumes of activation for dimethyl sulfoxide and N,N-dimethylformamide exchange with hexasolvates of aluminum(III) and gallium(III) ions in deuterionitromethane solution

High‐pressure 1H‐NMR. has been used to determine volumes of activation (ΔV #) for solvent exchange with [M(S)6]3+ ion (M = Al(III), Ga(III); S = dimethylsulfoxide (DMSO) and N,N‐dimethylformamide (DMF)) in [2H]3‐nitromethane solution. For Al(III),Δ V # = + 15.6 ± 1.4 (S = DMSO, 358.5 K) and ΔV # = + 13.7 ± 1.2 cm3mol−1 (S = DMF, 354.5 K), whilst for Ga(III), ΔV # = + 13.1 ± 1.0 (S = DMSO, 334.6 K) and ΔV # = +7.9 ± 1.6 cm3mol−1 (S= DMF, 313.8 K). Variable temperature studies over a temperature range of 107.2 K (Al(III)) and 101.1 K (Ga(III)) were carried out for solvent exchange with [M(DMF)6]3+ ions in [2H]3‐nitromethane solution, using stopped‐flow NMR, and conventional linebroadening, and gave ΔH # = 88.3 ± 0.9 and 85.1 ± 0.6 kJ+ mol−1, and ΔS # = 28.4 ± 2.7 and 45.1 ± 1.9 JK−1 mol−1 for Al(III) and Ga(III) ions respectively. All of these results are consistent with dissociative modes of activation.