Isomerization and Oxygen Atom Transfer Reactivity in Oxo−Mo Complexes of Relevance to Molybdoenzymes

Both dioxo Mo(VI) and mono-oxo Mo(V) complexes of a sterically
restrictive N2O heteroscorpionate ligand are found to exist as cis
and trans isomers. The thermodynamically stable isomer differs
for the two oxidation states, but in each case, we have isolated
the kinetically labile isomer and followed its isomerization to the
thermodynamically stable form. The Mo(VI) complex is more stable
in the cis geometry and isomerizes more than 6 times faster than
the Mo(V) complex, which prefers the trans geometry. In OAT
reactions with PPh3, the trans isomer of the dioxo−Mo(VI) reacts
∼20 times faster than the cis isomer. Thus, there are both oxidation
state and donor atom dependent differences in isomeric stability
and reactivity that could have significant functional implications
for molybdoenzymes such as DMSO reductase.