Multinuclear magnetic resonance study of sterically crowded stannylphosphines and stannylamines : stereochemical influences on chemical shielding and spin-spin couplings

Abstract

Multinuclear (1H, 15N, 29Si, 31P, 119Sn) NMR data of sterically crowded acyclic stannylphosphines tBu3SnPHY (Y = H, SnMe3, SntBu3, SiMe3; 1-3, 10), (tBu2RSn)2PH (R = Me, Cl; 4, 5), tBu3SnPY2 (Y = SnMe3, SiMe3; 6, 11), PH(SntBu2PHSntBu3)2 (7), SntBu2(PY2)2 (Y = H, SiMe3, PHSntBu3; 8, 9, 12), cyclic stannylphosphines (tBu2SnPY)n (n = 2, Y = H, C3H6Cl, tBu, SnMe3; 13-16; n = 3, Y = H; 18), (Me2SnPSntBu3)2 (17), and stannylamines tBu3SnNHY (Y = H, SnMe3, SntBu3; 19-21) were obtained by various 1D- and 2D-techniques. 31P- and 15N-shieldings may be explained qualitatively in terms of two counteracting influences, viz electronegativity differences and steric requirements of the substituents. In a similar manner, the trends in one-bond coupling 1KSnP and 1KSnM may be rationalized using a simple model based on the deformation of bond angles by sterically demanding substituents. The signs of long-range couplings 2KSnPH and 1KPSnCCH could be determined, which may be useful for future structural studies. Temperature-dependent effects in the spectra of 13, 18 allow conclusions about the conformational dynamics of the molecules.