Electrospray ionization in the study of sol-gel processes: the polycondensation of Ti(O-n-Bu)(4) in the presence of Si(OEt)(4)

The polycondensation of Ti(O-n-Bu)(4) in presence of Si(OEt)(4) (Et = C2H5, Bu = C4H9) has been studied by electrospray ionization of their mixtures in methanol. Series of oligomers due to Ti(oMe)(4) (Me = CH3) polycondensation have been detected and represent the most abundant species. This result can be explained by the ready alcoholysis of Ti(O-n-Bu)(4) and by its fast kinetics of oligomerization. However a series of Ti,Si-containing oligomers, with molecular weights in the range 400-1300 Da, has also been detected. Their structures have been characterized by isotopic cluster analysis and MS/MS experiments, proving that they originate by reaction of Ti-OH and Si-OEt moieties.