Showing papers by "George M. Sheldrick published in 1981"
58 citations
50 citations
TL;DR: In this paper, the 1 : 1 reaction between [Bu4N][Au(C6F5)2] and AgCIO4 in dichloromethane gives yellow solutions, from which solids of stoicheiometry AgL can be precipitated by the addition of O, N, S or P-donors, L; and X-ray diffraction study for L = SC4H8 reveals [AuAg]2 rings linked by Au ⋯ Au interactions to form infinite metal-atom chains.
Abstract: The 1 : 1 reaction between [Bu4N][Au(C6F5)2] and AgCIO4 in dichloromethane gives yellow solutions, from which solids of stoicheiometry Au(C6F5)AgL can be precipitated by the addition of O, N, S, or P-donors, L; and X-ray diffraction study for L = SC4H8 reveals [AuAg]2 rings linked by Au ⋯ Au interactions to form infinite metal-atom chains.
49 citations
TL;DR: The X-ray structure analysis of the synthetic analogue of the antibiotic triostin A, TANDEM, is reported, which binds preferentially to alternating adenine-thymine sequences7 and suggests possible models for the binding of other members of the quinoxaline series.
Abstract: Quinoxaline antibiotics (Fig. 1a, b) form a useful group of compounds for the study of drug–nucleic acid interactions1,2. They consist of a cross-bridged cyclic octadepsipeptide, variously modified, bearing two quinoxaline chromophores. These antibiotics intercalate bifunctionally into DNA2,3 probably via the narrow groove, forming a complex in which, most probably, two base pairs are sandwiched between the chromophores4,5. Depending on the nature of their sulphur-containing cross-bridge and modifications to their amino acid side chains, they display characteristic patterns of nucleotide sequence selectivity when binding to DNAs of different base composition and to synthetic polydeoxynucleotides4,6,7. This specificity has been tentatively ascribed to specific hydrogen-bonding interactions between functional groups in the DNA and complementary moieties on the peptide ring2,4,5. Variations in selectivity have been attributed both to changes in the conformation of the peptide backbone6 and no modifications of the cross-bridge7. These suggestions were made, however, in the absence of firm knowledge about the three-dimensional structure and conformation of the antibiotic molecules. We now report the X-ray structure analysis of the synthetic analogue of the antibiotic triostin A, TANDEM (des-N-tetramethyl triostin A) (Fig. 1c), which binds preferentially to alternating adenine-thymine sequences7. The X-ray structure provides a starting point for exploring the origin of this specificity and suggests possible models for the binding of other members of the quinoxaline series.
47 citations
TL;DR: A single-crystal X-ray structural investigation of the material previously known as ‘Ag2O II’ has shown the correct empirical formula to be Ag3O.
Abstract: A single-crystal X-ray structural investigation of the material previously known as ‘Ag2O II’ has shown the correct empirical formula to be Ag3O.
38 citations
38 citations
31 citations
TL;DR: The first four-coordinate gold(I) complex whose structure has been fully determined by X-ray diffraction was reported in this article. But the structure has not yet been confirmed.
Abstract: The addition of 1,10-phenanthroline, o-phenylenebis(dimethylarsine), or triphenylstibine to pentafluorophenyl-(tetrahydrothiophen) gold(I) leads respectively to [Au(C6F5)(phen)], [Au(pdma)2][Au(C6F5)2], and [Au(SbPh3)4][Au(C6F5)2], the pdma derivative being the first four-co-ordinate gold(I) complex whose structure has been fully determined by X-ray diffraction; space group P, a= 10.340(3), b= 10.982(3), c= 17.612(5)A, α= 75.45(2), β= 82.35(2), γ= 87.23(2)°, Z= 2, R= 0.043 for 5 558 unique observed reflections. The Au– As bond lengths range from 2.462 to 2.478 A. The two independent anions are exactly linear at Au.
31 citations
TL;DR: In this paper, the thermische LiF-Abspaltung aus Lithio-aminofluorsilane ist ein einfacher Syntheseweg fur viergliedrige Silicium-Stickstoff-Ringe.
Abstract: Lithio-aminofluorsilane werden in der Reaktion von Aminofluorsilanen mit Butyllithium erhalten. Die thermische LiF-Abspaltung aus Lithio-aminofluorsilanen ist ein einfacher Syntheseweg fur viergliedrige Silicium-Stickstoff-Ringe. Rontgenstrukturuntersuchungen wurden von 1,3-Bis(3,5-dimethylphenyl)-2,2,4,4-tetramethyl-1,3-diaza-2,4-disilacyclobutan und von 2,4-Di-tert.-butyl-2,4-difluor-1,3-bis(2,4,6-trimethylphenyl)-1,3-diaza-2,4-disiacyclobutan durchgefuhrt.
22 citations
19 citations
TL;DR: In this paper, the tetrahydrothiophen group (tht) in [Au(C6F5)3(tht)] can readily be replaced by carbonylmetallate anions [M(Co)n] or [NBun4] whose reactivity with PPh3 depends upon M.
Abstract: The tetrahydrothiophen group (tht) in [Au(C6F5)3(tht)] can readily be replaced by carbonylmetallate anions [M(Co)n]–(M = Co, n= 4; M = Mn, n= 5) or [M(cp)(CO)3]–(M = Mo or W; cp =η-C5H5) to give a novel type of anionic complex of general formula [N(PPh3)2][(C6F5)3Au–M(CO)n] or [NBun4][(C6F5)3Au–M(cp)-(CO)3] whose reactivity with PPh3 depends upon M. Thus, for M = Mo or W the reaction leads to the cleavage of the metal–metal bond, for M = Mn no reaction is observed at room temperature, whilst substitution of one CO group takes place for M = Co. Reaction of the carbonylmetallates with [Au(C6F5)(tht)] gives rise to disproportionations affording Q[Au(C6F5)2][Q = N(PPh3)2+ or NBun4+] and [N(PPh3)2][Au{M(CO)n}2] or [NBun4]-[Au{M(cp)(CO)3}2] which are stable at room temperature. The presence of the linear unit CO–Au–Co in [N-(PPh3)2][Au{Co(CO)4}2] has been established by a single-crystal structure determination; space group P, a= 9.610(4), b= 9.978(4), c= 11.506(5)A, α= 97.70(2), β= 97.84(2), γ= 90.97(2)°, and Z= 1. The structure has been refined to R= 0.032 for 2 475 unique observed reflections. Both the anion and cation lie on crystallographic centres of symmetry, hence the Co–Au–Co and P–N–P moieties are linear. The Au–Co bond length is 2.509(2)A.
TL;DR: In this paper, the crystal structure of trans-[Mn(NSF3)4(AsF6)2] was shown to be octahedrally co-ordinated, with Mn-Nav. 2.187, Mn-F 2.193, and N-S bonds appreciably stronger than in free NSF3.
Abstract: The i.r. spectra of the series [M(NSF3)4(AsF6)2](M = Mn, Fe, Co, Ni, or Cu) indicate that the compounds are isostructural, with trans-AsF6 groups co-ordinated to the metal atom, and N–S bonds appreciably stronger than in free NSF3. This is confirmed by the crystal structure of trans-[Mn(NSF3)4(AsF6)2]. It crystallises in the monoclinic space group P21/n, with a= 7.496(4), b= 10.378(5), c= 13.979(6)A, β= 94.33(3)°, and Z= 2. The structure was refined to R= 0.048 for 1 226 diffractometer data. The metal ion is octahedrally co-ordinated, with Mn–Nav. 2.187, Mn–F 2.193(4), and N–Sav. 1.365 A.
TL;DR: In this paper, the crystal structure of the title compounds Ph2MePAuC4S4AuPMePh2(1), prepared from Ph2mePAuCl and the anion of tetrathiosquaric acid, was determined (monoclinic, space group C2/C, Z = 4).
Abstract: Die Struktur der Titelverbindung Ph2MePAuC4S4AuPMePh2(1), die aus Ph2MePAuCl und dem Anion der Tetrathioquadratsaure zuganglich ist, wurde bestimmt (monoklin, Raumgruppe C2/c, Z = 4). Tetrathioquadratat tritt als Brucke zwischen den Goldatomen auf; die beiden Chelatringe der Adjuvans-Arthritis der Ratte.
Properties and Structure of μ-Tetrathiosquarato-bis[(methyldiphenylphosphane)gold(I)]
The crystal structure of the title compounds Ph2MePAuC4S4AuPMePh2(1), prepared from Ph2MePAuCl and the anion of tetrathiosquaric acid, was determined (monoclinic, space group C2/C, Z = 4). The gold atoms are bridged by the tetrathiosquarate ligand. The two chelate rings are distorted (AuS: 236.4 and 295.2 pm). 1 showed no effects on adjuvans-arthritis in rats.
TL;DR: The compound Au₂(SeO₃)₆(Se₁O) was prepared from gold metal and seienic acid at 553 K and the crystal structure [C2/c, a = 2034.4(5), b = 413.0(1), c = 1325.4
Abstract: The compound Au₂(SeO₃)₂(Se₂O₅) was prepared from gold metal and seienic acid at 553 K. The crystal structure [C2/c, a = 2034.4(5), b = 413.0(1), c = 1325.4(3) pm, β = 115.88(3)°, Z = 4] was refined to R = 0.035. Both gold atoms lie on crystallographic centres of symmetry and show square planar coordination (Au-0 196.9-201.3 pm). The extended structure consists of three cross-linked systems of the form [··· -Au-(selenite or diselenite) -Au-···].
TL;DR: Hellwinkel et al. as mentioned in this paper determined the structure of dibenzo(def, pqrltetraphenylene (I), a bi-4,5-phenanthrylene (Thulin & Wennerstr6m, 1977) to establish the molecular conformation.
Abstract: C28H16 , M r = 35244, monoclinic, Cc, a = 30492(4), b = 7405(4), c = 16362 (4)A, fl = 10530 (1) °, U = 35635 A 3, Z = 8, D x = 1314 Mg m -3, ~(Mo K~t) = 0069 mm -1 The structure was solved by incorporating trio relations into the starting set for multisolution direct methods, and refined to R = 0048 for 3947 unique observed reflexions The molecule shows a distorted tub conformation The phenanthrene moieties are twisted considerably The racemate consists of helical PP and MM enantiomers Introduction Cyclooctatetraene and its derivatives show non-planar tub conformations (Fray & Saxton, 1978) Tetraphenylene, a tetrabenzocyclooctatetraene, has the same geometry (Irngartinger & Reibel, 1981) Some bridged tetraphenylene derivatives have been synthesized and non-planar conformations postulated from spectroscopic data (Hellwinkel & Haas, 1979; Hellwinkel, Reiff & Nykodym, 1977) We determined the structure of dibenzo(def, pqrltetraphenylene (I), a bi-4,5-phenanthrylene (Thulin & Wennerstr6m, 1977), to establish the molecular conformation
TL;DR: In this paper, the properties of (dma) 2 HPF 6 and (da) 2 HSbF 6 were investigated by IR, 1 H and 19 F NMR spectroscopy.