31 P{ 1 H} NMR spectra were also found to be extremely diagnostic of the formation of 1-M. The free proligand exhibits a single resonance at -0.40 ppm, while deprotonation and coordination of AE metals or Yb to the methanide carbon changes the resonance frequency to 20-30 ppm (Table ). The greatest difference was observed for 1-Mg (δP = 30.1 ppm, centre of grouping). The heavier analogues of 1-M (M = Ca, Sr, Ba, Yb) consistently exhibited P NMR resonances around 20 ppm. The complementary 2 JPH coupling could not be observed in the P{ 1 H} NMR spectrum due to interference with the more complex splitting pattern from P-H coupling with the phenyl rings. In the 31 P{ 1 H} NMR of 1-Yb, 171 Yb satellites could be observed, with a 2 JPYb coupling constant of 90-95 Hz (Figure , inset). Yb-P coupling is mainly reported for JYbP which is much larger in magnitude (500-900 Hz).