Empirical calculations of Si-29 NMR chemical shielding tensors: A partial charge model investigation of hydrolysis in organically modified alkoxy silanes

The Si-29 NMR chemical shifts for a series of organically modified silane compounds, MexSi(OR)(y)(OH)(4-x-y) (OR = OMe, OEt), were evaluated using a partial charge model (PCM) approach to describe the chemical bonding. These PCM results allow the relative contributions of the diamagnetic and paramagnetic terms in the Si-29 NMR chemical shielding constant to be discussed. An explanation for the unique variations in the Si-29 chemical shifts during for hydrolyzed organically modified silanes is presented.