One‐ and two‐dimensional 15N NMR spectroscopy of tris(trimethylsilyl)‐, tris(trimethylstannyl)‐, tris(trimethylplumbyl)‐amine and tetrakis(trimethyistannyl)hydrazine: Sign determination of various scalar coupling constants

The signs of the coupling constants 1J(29Si15N) and 1J(119Sn15N) are positive and negative, respectively, in tris(trimethylsilyl)‐ and tris(trimethylstannyl)‐amine. This results from two‐dimensional (2D) 15N/1H heteronuclear shift correlations [at natural abundance of 15N, based on long‐range couplings 3J(1N 1H), with respect to the positive coupling constants 2J(29SiC 1H) and 2J(119SnC 1H)]. The same type of experiment proves the negative sign of 1J(119Sn15N) in tetrakis(trimethylstannyl)hydrazme and it allows the unambiguous assignment of 1J(119Sn15N) and 2J(119SnN 15N). In tris(trimethylplumbyl)‐amine, the largest value (335.7 Hz) reported so far for 1J(207Pb 15N) of plumbylamines is observed. In the case of tris(trimethylstannyl)amine, the 2D 15N/1H experiment also gave the sign of 4J(119SnNSnC1H) (positive), and this is used in the 2D 119Sn/1H experiment to prove a negative sign for 2J(119Sn 117Sn).