(2) replacing one Me3Si on the hexamethyldisilazides with i-Pr and t-Bu groups shifts the resonance upfield by <1 and 4 ppm, respectively; and (3) the most important parameter-deaggregating a dimer to a monomer-imposes a 3-8 ppm upfield shift, and ionizing the monomer causes an additional 3-6 ppm upfield shifts. There is some doubt about the contributions of ion pairs (7) that might be time averaging with the species assigned as monomers (6) in Table ; it would be difficult to detect low levels of ionization. Overall, the most upfield shifted 29 Si resonances are observed for KBTA, suggesting ion pair may be contributing.