PROTONATION OF DIARYLCARBENES BY ALCOHOLS - THE IMPORTANCE OF ION-PAIR DYNAMICS

Picosecond laser excitation of either di(p-chlorophenyl)- or di(p-meth oxyphenyl)diazomethane generates a transient which we ascribe to the s inglet states of di(p-chlorophenyl)- and di(p-methoxyphenyl)carbenes, 1a and 1b, respectively. Picosecond absorption spectroscopy is used to determine their kinetic behavior in various solvents. In the presence of alcohols, these carbenes are protonated, forming contact-ion pairs . These ion pairs partition between collapse to ether products and sep aration to free carbeneium ions, 2a and 2b, which are readily observed . The dynamics of these ion pairs is discussed. Protonation of carbene s can provide an alternative method for the preparation of ion pairs a nd the investigation of their dynamics.