Ligand isotopic exchange of cis-bis(acetylacetonato)dioxomolybdenum(VI) in acetylacetone

The ligand exchange of cis-bis(acetylacetonato)dioxomolybdenum(VI) in acetylacetone has been studied kinetically with the 14C-labeling technique. The rate law was rate = (k1 + k2[H2O])[complex] at 5.0, 15.0, 25.0, and 35.00C; k1 and k2 are 1.05 x 10-3 s-1 and 8.27 x 10-3 s-1 at 250C, respectively. ΔH* and ΔS* are 64 +/- 2 and 64 +/- 1 kJ mol-1 and -86 +/- 5 and -71 +/- 4 J K-1 mol-1 for k1 and k2, respectively. Dilution of the solvent with acetonitrile and deuteriation of the acidic hydrogens of the solvent and of water decreased both rate constants. Application of pressure to the solution up to 92 MPa at 50C caused no significant change in the rate law, and the rates themselves, i.e. ΔV double dagger s, were ca. 0 cm3 mol-1. The mechanism of the reaction in discussed on the basis of these data