Silylmethyl and silylamino groups as ligands in tin(II), tin(IV), lead(II) and lead(IV) compounds—a multinuclear magnetic resonance study

Abstract

Abstract We have studied tin(II), tin(IV), lead(II) and lead(IV) compounds of the type M[CH(SiMe3)2]2 (5), M[N(SiMe3)2]2 (6), M[N(SiMe3)SiMe2tBu]2 (7), Me3MCH2SiMe3 (1), Me3MCH(SiMe3)2 (3), Me3MNHSiMe2tBu (2), Me3MN(SiMe3)2 (4), Me2M[N(SiMe3)2]2, (8) and (Me3M)2NSiMe2tBu (9) by 13C, 15N, 29Si, 119Sn and 207Pb NMR spectroscopy. In some cases, two-dimensional (2-D) 13C/1H and 29Si/1H heteroscalar-correlated NMR spectra served for the comparison of the signs of the respective coupling constants [nJ(M 13C), 2J(M29Si) and nJ(M1H)]. The 13C and 15N NMR parameter of comparable compounds (replacement of the CH or CH2 fragment by a nitrogen atom or the NH group, respectively), show analogous trends. In the monomeric M(II) compounds (5, 6, 7) the peculiar electronic situation at the metal is reflected by the extreme deshielding of the metal nuclei (e.g. δ207 Pb for 5b = +9110 ppm), by the strongly deshielded 13C (5) and 15N nuclei (6, 7), as well as by large negative contributions to the reduced nuclear spin—spin coupling constants 1K(M13C) (5) and 1K(M15N) (6). In the M(II) compounds 5 the 119Sn and, in particular, the 207Pb longitudinal and transverse nuclear relaxation is dominated by the chemical-shift-anisotropy mechanism. This is also true for 6 and 7, in which the transverse relaxation rate is further increased by scalar relaxation of the second kind owing to partially relaxed scalar coupling 1J(M14N).