MULTINUCLEAR MAGNETIC-RESONANCE STUDY OF STERICALLY CROWDED STANNYLPHOSPHINES AND STANNYLAMINES - STEREOCHEMICAL INFLUENCES ON CHEMICAL SHIELDING AND SPIN-SPIN COUPLINGS

Multinuclear (H-1, N-15, Si-29, P-31, Sn-119) NMR data of sterically c rowded acyclic stannylphosphines tBu(3)SnPHY (Y = H, SnMe(3), SntBu(3) , SiMe(3); 1-3, 10), (tBu(2)RSn)(2)PH (R = Me, Cl; 4, 5), tBu(3)SnPY(2 ) (Y = SnMe(3), SiMe(3); 6, 11), PH(SntBu(2)PHSntBu(3))2 (7), SntBu(2) (PY2)2 (Y = H, SiMe(3), PHSntBu(3); 8, 9, 12), cyclic stannylphosphine s (tBu(2)SnPY)(n) (n = 2, Y = H, C3H6Cl, tBu, SnMe(3); 13-16; n = 3, Y = H; 18), (Me(2)SnPSntBu(3))(2) (17) and stannylamines tBu(3)SnNHY (Y = H, SnMe(3), SntBu(3); 19-21) were obtained by various 1D- and 2D-te chniques. P-31- and N-15-shieldings may be explained qualitatively in terms of two counteracting influences, viz electronegativity differenc es and steric requirements of the substituents. In a similar manner, t he trends in one-bond coupling K-1(SnP) and (1)KSnM may be rationalize d using a simple model based on the deformation of bond angles by ster ically demanding substituents. The signs of long-range couplings K-2(S nPH) and K-1(PSnCCH) could be determined, which may be useful for futu re structural studies. Temperature-dependent effects in the spectra of 13, 18 allow conclusions about the conformational dynamics of the mol ecules.