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1998[X]
1Author    Bernd Wrackmeyer3, Jürgen Weidinger3, Heinrich Nöthb, Wolfgang Storchb, Thomas Seifertb, Martina VosteenbRequires cookie*
 Title    Determination of Coupling Signs 17 (119Sn, 15N ) and 2/ ( 119Sn, 117Sn) in Trimethylstannylamines  
 Abstract    The l5N-labelled trimethylstannylamines 1 -3 [(M e3Sn)3N, (M e3Sn)2NPh, (M e3Sn)2N-BCgHi4 (BCgHi4 = 9-borabicyclo[3.3.0]nonyn and the non-labelled 4, Me3 Sn-N(BC8Hi4)2 , were prepared and studied by 1H, 1 C, l5N and l9Sn NMR. The l5N ultrahigh resolution NMR spectra of 1 revealed otherwise unobserved parameters such as 2/ (15N ,S n ,'C) and the isotope induced chemical shift 2 zAl2/l3C (l5N). ll9Sn NM R spectra of 1, recorded under similar con­ ditions, also show new parameters such as V (' |ySn,N,Sn,l3C) which are not resolved in the non-labelled derivative. By using various types o f two-dimensional heteronuclear shift corre­ lations, absolute coupling signs o f l7 (l l9 Sn,15N) (all < 0) in 1 -3 were determined. By the same techniques it proved possible to confirm the negative sign o f :7(Sn,Sn) (-195.4 Hz) in 1. In contrast, the coupling constants 27(Sn,Sn) for 2 (+71.7) and 3 (+62.0) possess a positive sign. This sign inversion, observed here for the first time for apparently similar compounds, demonstrates the enormous influence o f substituents on the nature o f the lone pair o f electrons at the nitrogen atom. It also shows that these experiments for sign determinations o f coupling constants are necessary in order to interpret these data correctly. 
  Reference    Z. Naturforsch. 53b, 1494—1500 (1998); received July 30 1998 
  Published    1998 
  Keywords    Tin, Amines, NM R Data, Ultrahigh Resolution, Coupling Sign Determination 
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 TEI-XML for    default:Reihe_B/53/ZNB-1998-53b-1494.pdf 
 Identifier    ZNB-1998-53b-1494 
 Volume    53