29 Si{ 1 H} NMR spectra obtained using the method of continuous variation applied to KPTA and KBTA (0.10 M total concentration) in 0.20 TMEDA in cyclopentane at 0 ºC labeled with the intended mole fraction 9 (see Figure ). Owing to the broadening of the KBTA resonance of the heterodimer, only the KPTA component of the heteroaggregate was used to calculate the mole fraction.