Cationic germanium fluorides: 2. An experimental and theoretical investigation on the reaction between GeF+ and H2O

The reaction between singlet ground state GeF+ (1+) and H2O, with formation of Ge-OH+ and HF, has been investigated by ion trap mass spectrometry (ITMS) and ab initio calculations at the MP2 and CCSD(T) level of theory. The process occurs by the initial formation of the addition product FGe+-OH2 (1), its interconversion into HOGe+-FH (2), and the eventual barrier-free dissociation into Ge-OH+ and HF. The activation barrier of the 1 → 2 isomerization is comparable with the exothermicity (exoergicity) of the formation of 1, and this explains the relatively low efficiency of the process, experimentally evaluated as 0.14 from the ratio of the absolute rate constant, 3.2x10-10 cm3 molecule-1 s-1, and the collisional rate constant. The mechanism of the reaction between GeF+ and H2O is strictly analogue to that of the reaction between SiF+ and H2O, investigated so far by selected-ion flow tube (SIFT) mass spectrometry and ab initio calculations. From the general point of view, the conceivable occurrence of other similarities between the still essentially unexplored reactiviy of GeFn+ (n =1-3) and the rich and variegated chemistry of SiFn+ suggests novel attractive opportunities in the gas-phase positive ion chemistry of germanium.