Generation and characterization of protonated silicic acid Si(OH)3+ and its neutral counterpart by tandem mass spectrometry and computational chemistry

Dissociative electron ionization of triethoxysilane, HSi(OC2H5)3, and tetraethoxysilane, Si(OC2H5)4, generates m/z 79 ions of composition [Si, O3, H3]+. From tandem mass spectrometry experiments and CBS-QB3 model chemistry calculations, it is concluded that these ions have the structure of protonated silicic acid, Si(OH)3+ (1a+), for which ΔHf(298K)=−36.3kcalmol−1 (for the anti-isomer). Low energy (metastable) ions 1a+ dissociate via loss of …