N-triorganostannyl-substituted pyrroles and indoles and N-trimethylstannylcarbazole:: Determination of signs of coupling constants and isotope-induced chemical shifts 1Δ14/15N(119Sn)

N-Triorganostannyl (R3Sn)-substituted pyrroles (1) and indoles (2) [R = Me (a), Et (b),Bu-t (c)], N-trimethylstannyl-carbazole (3), N-trimethylstannyl-2,5-dimethylpyrrole (Id), the corresponding silicon and lead derivatives [1d(Si) and 1d(Pb)] and N-trimethylstannyl-2-methylindole (2d) were prepared and studied by multinuclear magnetic resonance (H-1, C-13, N-15, Si-29, Sn-119 and (207)pb NMR). The absolute signs of numerous coupling constants (n)J(Sn-119,C-13) and (1)J(Sn-119,N-15) (< 0) were determined by appropriate 2D heteronuclear shift correlations of the type C-13/H-1 and N-15/H-1. Precise measurement of the coupling constants (1)J(Sn-119,N-15) from Sn-119 NMR spectra by using Hahn-echo extended (HEED) polarization transfer pulse sequences enabled one to obtain isotope-induced chemical shifts (1) Delta(14/15)N(Sn-119) at natural abundance of N-15. The (1) Delta(14/15)N(Sn-119) data become more negative with increased branching of the substituent R at the tin atom and with stronger steric interactions. The latter effect is also evident from delta(119)Sn values and changes in the magnitude of the coupling constants (1)J(Sn-119,C-13) or (1)J(Sn-119,N-15). (C) 1998 John Wiley & Sons, Ltd.