In notably, reactivity of 1-Yb was very smooth, leading to complete conversions at mild conditions. We observed a rough correlation between ionic radius (an approximation for the ionic character of the bonding) and the 13 C{ 1 H} chemical shift along with the 1 JCP coupling constant of the methanide carbon, particularly across the 1-M series. A similar pattern was YbI2(THF)2, N-trimethylsilylimino-P,P-diphenylphosphoranomethane were prepared according to literature procedures. TMS NPC-H2 was prepared according to a modified literature procedure (vide infra). λmax/nm ( /mol -1 cm -1 ) = 288 (6700).