Showing papers by "Sean Parkin published in 1994"
TL;DR: Variolin B (1), a new type of pyridopyrrolopyrimidine alkaloid with antitumour and antiviral properties, has been isolated from the Antarctic sponge Kirkpatrickia varialosa, and its structure determined by X-ray crystallography.
169 citations
TL;DR: The structure of compound 1 belongs to a series of dihydrogen complexes of osmium(II) amines, exhibiting an extensive range in the strength of the H-H interaction as judged by the wide variation in observed J[sub H-D] coupling constants.
Abstract: The structure of [Os([eta][sup 2]-H[sub 2])en[sub 2]CH[sub 3]CO[sub 2]]PF[sub 6] (1) has been studied by X-ray diffraction at 120 K and neutron diffraction at 165 K. Compound 1 belongs to a series of dihydrogen complexes of osmium(II) amines, exhibiting an extensive range in the strength of the H-H interaction as judged by the wide variation in observed J[sub H-D] coupling constants. The ethylenediamine ligands in I have a trans arrangement. The H[sub 2] and the acetate ligands occupy positions on opposite sides of the OsN[sub 4] plane, giving overall approximately octahedral coordination. Consistent with the relatively low J[sub H-D] value (9.0 Hz), the H-H distance in 1.134(2) [angstrom] as determined by neutron diffraction, is unusually long and approaches that of 1.357(7) [angstrom] found in the polyhydride ReH[sub 7][P(p-tolyl)[sub 3]][sub 2]. It is presumed that I may represent an intermediate stage in the oxidative addition of dihydrogen at transition-metal centers. The Os-H distances in 1.1.59(1) [angstrom] and 1.60(2) [angstrom], are shorter than those in the classical osmium polyhydride OsH[sub 4](PMe[sub 2]Ph)[sub 3] (mean Os-H 1.659(3) [angstrom]) lending support to the assertion that the Os([eta][sup 2]-H[sub 2]) interaction is relatively strong. Crystal data are provided. 46 refs., 3 figs., 2 tabs.
69 citations
TL;DR: In this paper, the synthesis and spectroscopic and structural characterization of several unassociated amido derivatives of aluminum and gallium have been described by simple salt elimination procedures and characterized by H and 13C NMR and X-ray crystallography.
67 citations
TL;DR: In this paper, 2,3-Bis(dibenzylamino)-and 2, 3-bis[allyl(benzyl)amino]-2Z-butene-1,4-dinitriles are macrocyclised by reaction with magnesium propoxide in propanol to provide the corresponding (porphyrazinato)magnesium(II) derivatives, the structures of which are confirmed by X-ray crystallographic studies of the title magnesium and nickel(III) complexes.
Abstract: 2,3-Bis(dibenzylamino)- and 2,3-bis[allyl(benzyl)amino]-2Z-butene-1,4-dinitriles are macrocyclised by reaction with magnesium propoxide in propanol to provide the corresponding (porphyrazinato)magnesium(II) derivatives, the structures of which are confirmed by X-ray crystallographic studies of the title magnesium and nickel(II) complexes; cyclisation of alternative diaminomaleonitrile derivatives gives the corresponding porphyrazinoctamines.
24 citations
14 citations
2 citations
TL;DR: The TiCl 2 moiety of 2,2'-ethylenebis(η 5 -indenyl)titanium dichloride, [TiCl 2 (C 20 H 16 )], spans the mirror plane in space group Pnma as mentioned in this paper, forcing disorder of the bridged bis-indeniyl ligand.
Abstract: The TiCl 2 moiety of 2,2'-ethylenebis(η 5 -indenyl)titanium dichloride, [TiCl 2 (C 20 H 16 )], spans the mirror plane in space group Pnma, forcing disorder of the bridged bis-indenyl ligand. The Ti centre has a distorted tetrahedral geometry; the (η 5 -centroid)-Ti-(η 5 -centroid) angle is 128.6 (2) o . The indenes bend away from the TiCl 2 moiety, which twists 19.1 (2) o out of the cavity between the indenes
2 citations