Coupling Sign Determination and Isotope-Induced Chemical Shifts1Δ15/14N(29Si),1Δ15/14N(119Sn) and1Δ29/28Si(15N): Multinuclear Magnetic Resonance Study ofN-Trimethylsilyl-, -stannyl- and -plumbyl-Substituted 2-Aminopyridines, 2,6-Diaminopyridines and Analogous 2-Picolines
作者:Bernd Wrackmeyer、Gerald Kehr、Hong Zhou、Saqib Ali
DOI:10.1002/(sici)1097-458x(199611)34:11<921::aid-omr987>3.0.co;2-9
日期:1996.11
2-Aminopyridines (1), 2-amino-3-methylpyridines (2) and 2,6-diaminopyridines (3), bearing N-trimethylsilyl, -stannyl or -plumbyl groups, and analogously substituted 2-picolines (4) were studied by H-1, C-13, N-15, Si-29, Sn-119 and (207)pb NMR spectroscopy Intramolecular N-Sn coordination became evident in the case of N,N-trimethylsilyl(trimethylstannyl)-2-aminopyridine (1e) and N,N-trimethylsilyl(trimethylstannyl)-N-trimethylsilyl-2,6-diaminopyridine (3f), in particular from their delta(15)N(amine) and delta(119)Sn data. Numerous coupling constants J(M,N-15) and J(M,C-13) (M=Si-29, Sn-119, Pb-207) were measured and, in the case of 2-/trimethylsilyl(trimethylstannyl)/methylpyridine (4e), absolute signs of (n)J(Sn-119,C-13) and (n+1)J(Sn-119,H-1) were determined by appropriate 2D C-13/H-1 heteronuclear shift correlations. Isotope-induced chemical shifts (1) Delta(15)/N-14(Si-29) (range -9 to -16 ppb) and (1) Delta(15/14)N(Sn-119) (range -32 to -55 ppb) were measured at natural abundance of N-15 by using Hahn-echo extended polarization transfer pulse sequences. (1) Delta(29/28)Si(N-15) values (range of -2.4 to -6.0 ppb) were measured from N-15 NMR spectra.