Gas-phase ion chemistry of Ti(O-i-Pr)4

Abstract

The positive and negative gas-phase ion chemistry of Ti(O-i-Pr)4 was investigated at low pressures by FT-ICR. The fragment ion, (i-PrO)3Ti-O+=C(H)Me, reacts with the parent neutral by proton transfer and by a nucleophilic addition–elimination reaction. The nature of the fragment ion and the ensuing ion–molecule reactions clearly indicate that Ti(O-i-Pr)4 exists as a monomer in the gas phase. In the negative ion mode, F– was found to react easily with Ti(O-i-Pr)4 to yield the pentacoordinated complex FTi(O-i-Pr)4– ion. This hypervalent Ti species undergoes a series of sequential fragmentations induced by IR multiphoton excitation. The first step is unusual because two channels are observed by IRMPD: one involves loss of HF, and the other loss of i-PrOH. The subsequent dissociation processes are characterized by progressive elimination of propene giving rise to a number of different titanaoxirane-containing anions with the general formula [(η2-CMe2O)Ti(OH)3–n(i-PrO)n]–. FTi(O-i-Pr)4– was also observed to undergo multiple alkoxide–fluoride exchanges with BF3 leading to the eventual formation of TiF5–.Key words: titanium tetraisoproxide, gas-phase ion chemistry, hypervalent Ti, ion–molecule reactions, IRMPD.