The reactivity of the neutral Cp2Ti(AsF6)2(Cp = C5H5) and the ionic Cp2Ti(CH3CN)32+(AsF6−)2toward water (D2O) has been investigated and elucidated by1H and19F NMR spectroscopy. Both compounds dissociate into ionic pairs. Due to the pH value (pH < 3.5, saturated solution) the titanocene group (Cp2Ti) remains intact (1H NMR). Also t h e AsF−6anion seems to be stable at the low pH value (19F NMR), aftera small amount (14–20%, relating t o F) has hydrolysed yielding DF, which was identified by 19F NMR spectroscopy. These results are important because titanocene and especially the hydrophilic cationic titanocene derivatives are of high interest in terms of their strong antiproliferative activity.