DEPROTONATION OF [HMO(CO)2(PP)2]BF4 COMPLEXES - HARD ANIONS AS PROTON CARRIERS
Additional Document Info
Reported are kinetic studies of the deprotonation of [HMo(CO)2(pp)2]BF4 complexes (PP= 1,2-bis(diphenylphosphino)ethane, dppe; PP = 1,2-bis(dimethylphosphino)ethane, dmpe; PP = 1,2-bis(diethylphosphino)ethane, depe). Amine bases deprotonated the metalloacids slowly, t1/2 typically being days, following the rate expression rate = k2[MoH+][amine]. Deprotonation rates were dependent on the size of the amine bases and were greatly enhanced by the addition of salts of hard anions such as halides and acetate. The rate expression for deprotonation by mixed-base systems loses dependence on [amine], substituting instead a dependence on [X-]. The dependence of rate on the steric and electronic nature of the pp ligand was interrelated with similar features of the base. Activation energy parameters, H/D kinetic isotope effects, and solvent effects suggest Mo-H bond breaking as well as coordination sphere rearrangement in the transition state. 1986, American Chemical Society. All rights reserved.