PROTONOLYSIS REACTIONS IN THE SERIES RMN(CO)5 AND RC(O)MN(CO)5

Proton cleavage (protonolysis) of the RMn bond in RMn(CO)5 complexes occurs readily and cleanly with CF3SO3H to give the corresponding RH compounds. The relative order of reactivity in the series of RMn(CO)5 compounds we have prepared is R H, CH3, Ph, p-CH3C6H4, p-BrC6H4, p-CF3C6H4 > PhCH2 > p-ClC6H4CH2 ≅ p-CH3OC6H4CH2 ≫ PhCH2CH2. Protonolysis with HBF4 is much slower than with triflic acid in every case. The reaction with both acids very likely proceeds by attack of the proton on Mn followed by reductive elimination. Surprisingly, the corresponding RC(O)Mn(CO)5 compounds on treatment with triflic acid do not undergo protonolysis to aldehydes. Instead, hydroxycarbenes are formed reversibly and the acyls are slowly decarbonylated to RMn(CO)5 which then undergo protonolysis and reductive elimination to give quantitative yields of RH. © 1990.