Browsing by Author "Daniels, Lee M."

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    New azasilatranes: bidentate and tridentate coordination modes of the novel ligand EtOSi(Ph2PNCH2CH2)2(HNCH2CH2)N
    (1990) Gudat, Dietrich; Daniels, Lee M.; Verkade, John G.
    The synthesis and characterization of EtOSi(Ph2PNCH2CH)2(HNCH2CH2)N (ethoxy-N,N'·bis(di-phenylphosphino)azasilatrane, the title compound 3b) is reported. Its reactions with sulfur and MeI proceed easily via quaternization at the phosphorus sites to give the bis(phosphonium) salt and the bis(phosphine) sulfide, respectively. Synthesis and characterization of the coordination compounds (3b) Ni(CO)2, (3b) PtCl2, (3b) M(CO)4 (M = Mo, W), and (3b) M(CO)3 (M = Mo, W) give evidence for the existence of two possible coordination modes; one wherein 3b behaves as a bidentate (P,P') ligand and the other as a tridentate (P,P',O) ligand. The latter coordination mode provides a rare example of coordination of a silyl ether to a transition metal. NMR spectroscopic studies in solution and the solid state establish the presence of transannular Si-N bonding and hypercoordination at silicon. Solid-state 31P NMR spectra give direct evidence for the presence of a twisted, helically chiral conformation of the silatranyl cage, which in solution is lost as a consequence of rapid conformational mobility on the NMR time scale. These findings are further corroborated by the results of crystal structure determinations of the bis(phosphine) sulfide and (3b) PtCl2.
  • Thumbnail Image
    ItemOpen Access
    New azasilatranes: sterically induced transannular bond weakening and cleavage
    (1989) Gudat, Dietrich; Daniels, Lee M.; Verkade, John G.
    Silylation of azasilatrane I (R = R1 = R2 = H) with ClSiMe3/NEt3 gives disilylated I (R = R1 = Me3Si, R2 = H) (II), via the spectroscopically detected monosilylated intermediate. Treatment of II with BuLi gives the stable lithiated deriv. I (R = R1 = Me3Si, R2 = Li) which can be converted to I [R = R1 = Me3Si, R2 = Me, Me3Si (III)], via reaction with MeI or ClSiMe3, resp. The novel structure of III, inferred from NMR data and confirmed by x-ray means, features an Nax nitrogen in a nearly trigonal pyramidal stereochem. with an exceptionally long NaxSi bond [ 2.775(7)?]. Reaction of III with MeOSO2CF3 gives IV, the Nax methylated product.