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N ‐Triorganostannyl‐substituted pyrroles and indoles and N ‐trimethylstannylcarbazole: determination of signs of coupling constants and isotope‐induced chemical shifts 1 Δ 14/15 N( 119 Sn)
Author(s) -
Wrackmeyer Bernd,
Kehr Gerald,
Maisel Heidi E.,
Zhou Hong
Publication year - 1998
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(199801)36:1<39::aid-omr209>3.0.co;2-w
Subject(s) - chemistry , heteronuclear molecule , chemical shift , steric effects , coupling constant , electronegativity , substituent , carbon 13 nmr , stereochemistry , crystallography , computational chemistry , nuclear magnetic resonance spectroscopy , organic chemistry , physics , particle physics
N ‐Triorganostannyl (R 3 Sn)‐substituted pyrroles ( 1 ) and indoles ( 2 ) [R=Me ( a ), Et ( b ), t Bu ( c )], N ‐trimethylstannyl‐carbazole ( 3 ), N ‐trimethylstannyl‐2,5‐dimethylpyrrole ( 1d ), 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 ( 1 H, 13 C, 15 N, 29 Si, 119 Sn and 207 Pb NMR). The absolute signs of numerous coupling constants n J ( 119 Sn, 13 C) and 1 J ( 119 Sn, 15 N) (<0) were determined by appropriate 2D heteronuclear shift correlations of the type 13 C/ 1 H and 15 N/ 1 H. Precise measurement of the coupling constants 1 J ( 119 Sn, 15 N) from 119 Sn NMR spectra by using Hahn‐echo extended (HEED) polarization transfer pulse sequences enabled one to obtain isotope‐induced chemical shifts 1 Δ 14/15 N( 119 Sn) at natural abundance of 15 N. The 1 Δ 14/15 N( 119 Sn) 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 δ 119 Sn values and changes in the magnitude of the coupling constants 1 J ( 119 Sn, 13 C) or 1 J ( 119 Sn, 15 N). © 1998 John Wiley & Sons, Ltd.