Physical organic chemistry of transition metal carbene complexes. 25. Kinetic and thermodynamic acidities of substituted (methylthiophenylcarbene)pentacarbonyl tungsten(0) and (benzoxymethylcarbene)pentacarbonyl tungsten(0) in aqueous acetonitrile. Evidence for transition state imbalances

The deprotonation of substituted (methylthiophenylcarbene)pentacarbonyl tungsten(0) ((CO)5W=C(SC6H4Z)CH3) and (benzoxymethylcarbene)pentacarbonyl tungsten(0) ((CO)5W=C(OCH2C6H4Z)CH3) in aqueous acetonitrile is studied. This indicates a transition state imbalance in which the loss of the carbene complex lags behind the proton transfer.