Solvent effects in the geometric reorganization of an oxo-molybdenum(V) system.

We have previously postulated a serine gated electron transfer hypothesis (Inorg. Chem, 2002, 41, 1281-1291) to possibly be involved in gating electron transfer between the Mo(V) and Mo(IV) states. In this study we explored the effect of solvent dielectric upon the rate and mechanism of isomerization of an oxo-Mo(V) core in attempt to understand the effect of solvent polarity to the isomerization reaction. To this end, the data suggests that there may be significant entropic contributions to the reorganization of metal center as a function of the local dielectric constant. Furthermore, we note that there is a change in the observed rate as well as the mechanism of the geometric rearrangement when it is examined in polar and non-polar environments. More specifically, in low dielectric media, the reaction proceeds either via a fast dissociation which is then followed by a twist mechanism or by a dissociation that is synchronized with the twist mechanism.