Showing papers by "George M. Sheldrick published in 1975"
TL;DR: In this article, the title compound (I) was solved by the heavy-atom method and refined by full-matrix least squares to R 0·047 for 1018 unique reflections measured by diffractometer.
Abstract: Crystals of the title compound (I) are orthorhombic, space group Pnma, a= 17·54(3), b= 14·55(2), c= 6·766(10)A, Z= 4. The structure was solved by the heavy-atom method and refined by full-matrix least-squares to R 0·047 for 1018 unique reflections measured by diffractometer. The molecule lies on a crystallographic mirror plane and possesses approximately C3ν(3m) symmetry; principal bond lengths (averaged for C3ν): Ru ⋯ Ru 2·842(6), Ru–C(O) 1·869(15) and 1·956(19), Ru–C(C) 2·083(11), C–O 1·152(16), and C–C 1·511(20)A. The bridging hydrogen atoms were located in symmetrical positions on the opposite side of the Ru3 plane from the CMe moiety; their positions were refined from the X-ray data subject to the constraints that all Ru–H and all (C)C–H distances were respectively equal, leading to Ru–H, 1·72(7)A and Ru–H–Ru, 112(7)°. The nematic-phase proton n.m.r. spectrum has been reinterpreted in the light of the idealised heavy-atom geometry found in the crystal, and used to give calculated values for Ru–H (1·81 A) and Ru–H–Ru (103°), which are probably more accurate than those calculated only from X-ray data.
27 citations
TL;DR: In this article, the 1H and 1H-{205Tl} INDOR spectra of dimethylthallium dimethylamide have been analyzed in terms of superimposed spectra for homonuclear and heteronuclear species.
Abstract: Variable-temperature 203Tl and 205Tl n.rn.r. spectra (with and without 1H-decoupling) and 1H-{205Tl} INDOR spectra of dimeric dimethylthallium ethoxide provide evidence of chemical exchange. The 1H and 1H–{205Tl} INDOR spectra of dimethylthallium dimethylamide have also been analysed in terms of superimposed spectra of homonuclear and heteronuclear species. The thallium–thallium coupling constant in both compounds has been determined. Thallium chemical shifts are also reported for related compounds.
7 citations
TL;DR: In this article, the title compound (I) was refined by full-matrix least-squares to R 0.076 for 2343 unique reflexions measured by diffractometer.
Abstract: Crystals of the title compound (I) are monoclinic, space group P21/c, a= 16.591(10), b= 10203(20), c= 16.164(10)A, β= 102.65(3)°, Z= 4. The structure was refined by full-matrix least-squares to R 0.076 for 2343 unique reflexions measured by diffractometer. In the cation there is distorted octahedral co-ordination of nickel by the quadridentate ligand and a 2-acetyipyridine molecule in the keto-form. There is evidence for disorder of the perchlorate anions. Ni–N Distances are 2.07–2.09 A for the quadridentate ligand; for the acetylpyridine, Ni–N 2.138(11), Ni–O 2.124(11), and CO 1.236 (13)A.
6 citations
TL;DR: In this paper, the structure of the DDT compound was solved by Patterson superposition methods from two-circle diffractometer data, and refined to R 0.048 for 3 545 unique observed reflections.
Abstract: Crystals of the title compound, produced by reaction of bis(dimethylglyoximato)pyridinecobalt(I) with 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (p,p′-DDT), are orthorhombic, space group Pn21a, a= 25.50(2), b= 23.13(2), c= 9.728(7)A, Z= 8. The structure was solved by Patterson superposition methods from two-circle diffractometer data, and refined to R 0.048 for 3 545 unique observed reflections. The asymmetric unit consists of two molecules, each with octahedral co-ordination of cobalt, which differ significantly only in the relative orientations of the aromatic rings and the effect this has on the bis(dimethylglyoximato) plane. A chlorovinyl group is σ-bonded to cobalt, with mean bond lengths: Co–C 1.970(13), CC 1.366(15), and C–Cl 1.803(13)A, mean Co–N distances are 2.042(10)(pyridine) and 1.877(10)A(oxime). The symmetry of the crystallographically independent O–H ⋯ O hydrogen bonds [O ⋯ O (mean) 2.50(1)A] is discussed. This σ-vinyl derivative may be relevant to the degradation of DDT in biological systems.
6 citations
5 citations
TL;DR: In this paper, the title compound (I) was refined by full-matrix least-squares to R 0.076 for 2343 unique reflexions measured by diffractometer.
Abstract: Crystals of the title compound (I) are monoclinic, space group P21/c, a= 16.591(10), b= 10203(20), c= 16.164(10)A, β= 102.65(3)°, Z= 4. The structure was refined by full-matrix least-squares to R 0.076 for 2343 unique reflexions measured by diffractometer. In the cation there is distorted octahedral co-ordination of nickel by the quadridentate ligand and a 2-acetyipyridine molecule in the keto-form. There is evidence for disorder of the perchlorate anions. Ni–N Distances are 2.07–2.09 A for the quadridentate ligand; for the acetylpyridine, Ni–N 2.138(11), Ni–O 2.124(11), and CO 1.236 (13)A.
TL;DR: In this article, the 1H and 1H-{205Tl} INDOR spectra of dimethylthallium dimethylamide have been analyzed in terms of superimposed spectra for homonuclear and heteronuclear species.
Abstract: Variable-temperature 203Tl and 205Tl n.rn.r. spectra (with and without 1H-decoupling) and 1H-{205Tl} INDOR spectra of dimeric dimethylthallium ethoxide provide evidence of chemical exchange. The 1H and 1H–{205Tl} INDOR spectra of dimethylthallium dimethylamide have also been analysed in terms of superimposed spectra of homonuclear and heteronuclear species. The thallium–thallium coupling constant in both compounds has been determined. Thallium chemical shifts are also reported for related compounds.