Showing papers by "George M. Sheldrick published in 1979"

Some reactions of dodecacarbonyltetrahydridotetraosmium with olefins; the molecular structure of 1,1,1,2,2,3,3,3,4,4,4-undecacarbonyl-1,2-µ-(1′-σ,1′–2′-η-cyclohexenyl)-tri-µ-hydrido-tetrahedro-tetraosmium

Abstract: The complexes [Os4(CO)11(cyclo-olefin – H)H3](cyclo-olefin = cyclo-octatetraene, cyclo-octa-1,5-diene, cyclo-hexene, or norbornene) have been identified as the products of reaction of [Os4(CO)12H4] with the appropriate cyclic olefin. The structures of these complexes are discussed in terms of available spectroscopic data and in the case of the title complex [Os4(CO)11(C6H9)H3] on the basis of a single-crystal X-ray analysis. This molecule crystallises in space group P21/n with a= 9.266(4), b= 14.850(8), c= 16.847(9)A, β= 93.39(3)°, and Z= 4. The osmium atoms define a tetrahedron, with the cyclohexene ring σ-bonded to one metal and π-bonded to another. The complex [Os4(CO)12H4] also reacts with the acyclic olefins CH2CH2, CH2CHPh, CH2CHCMe3, CH2CMeCMe3, and cis-CHPhCHPh to give the related complexes [Os4(CO)11(olefin – H)H3]. On heating, apart from the complex where the olefin is CH2CMeCMe3, dehydrogenation occurs to produce the dihydrido-complexes [Os4(CO)11(R1CCR2)H2](R1= H, R2= H, Ph, or CMe3; R1= R2= Ph). These complexes have been shown to contain a R1CCR2 fragment bound via two σ and one π bond to one tetrahedral face of the Os4 cluster unit.

X-Ray and neutron diffraction study of 1,1,1,2,2,2,3,3,3-nonacarbonyl-1,2;1,3-di-µ-hydrido-µ3-sulphido-triangulo-triosmium

Abstract: The title complex [Os3(CO)9H2(S)] crystallises in the monoclinic space group C2/c with a= 20.476(10), b= 13.952(7), c= 12.939(6)A, β= 123.84(3)°, and Z= 8. Simultaneous refinement of a single parameter set to 2 436 X-ray [(sinθ)/λ > 0.45] and 1 292 neutron data has led to R 0.038 (X-ray) and 0.037 (neutron). The two longer edges of the Os3 isosceles triangle are bridged by hydrides, which lie on the opposite side of the Os3 plane to the triply bridging sulphur atom. Each osmium is also bonded to three terminal carbonyls. The Os–H–Os linkages can be described as ‘open’ three-centre two-electron bent bonds, with little direct Os–Os interaction. Both hydride bridges are significantly asymmetric, the hydrogen atoms being ca. 0.025 A closer to the unique osmium. The mean Os–H distance is 1.819 A, and both Os–H–Os angles are 106.5(2)°.

Darstellung und Molekiilstruktur von 1.3.5.7-Tetraaza-2.4.6.8-tetrasila-bicyclo [3.3.0] octan/ Preparation and Molecular Structure of 1,3,5,7-Tetraaza-2,4,6,8-tetrasila-bicyclo[3,3,0]octane

Abstract: Abstract The structure of the title compound 1 has been determined from X-ray diffractometer data. 1 is formed by reaction of dilithiated hydrazine with N,N-bis(fluorodimethylsilyl)- 2,4,6-trimethylaniline. 1 has approximate D2 symmetry with planar nitrogen atoms. A >N-N<-unit is shared by the two five-membered rings.

The reaction of ethoxyquin (6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline) with nitrous acid

Abstract: The reaction of ethoxyquin (6-ethoxy-1,2-dihydro-2,2,4-trimethylquinotine) with acidified sodium nitrite solution over a short period at room temperature gives the unstable 1-nitroso derivative together with smaller amounts of the 8-nitro derivative and a quinone imine which has lost the ethyl group. The 8-nitroso derivative is observed fleetingly as a very readily oxidised intermediate. On being kept on silica gel the 1-nitroso derivative is partly transformed into the 8-nitro derivative and ethoxyquin itself, but the main product is the quinone imine. The crystal structures of 8-nitroethoxyquin (2) and of 6-acetoxy-1,2-dihydro-2,2,4-trimethylquinoline (7), the product of reduction–acetylation of the quinone imine, have been determined by X-ray analysis.