George A. Sim

Dolabellane diterpenoids from the liverwort Odontoschisma denudatum

Abstract Five new dolabellane diterpenoids have been isolated from the liverwort Odontoschisma denudatum, and their structures and absolute configurations have been determined on the basis of 1H and 13C NMR evidence and chemical correlation.

Preparation and characterization of two triphenylphosphineiron carbonyl complexes: X-ray crystallographic studies of (1–4-η-5-exo-benzylcyclopenta-1,3-diene)dicarbonyl(triphenylphosphine)iron(0), (1), and dicarbonyl(η-cyclopentadienyl)(triphenylphosphine)iron(II) 1,1,2,3,3-pentacyanopropenide, (2)

The complex [Fe(CH2Ph)(η-C5H5)(CO)2] undergoes a photochemical reaction with PPh3 to yield (1), which has been treated with tetracyanoethylene to yield (2). The products (1) and (2) have been identified and characterized by X-ray crystallography.

New cytotoxic diterpenes from Rondeletia panamensis (Rubiaceae).

Abstract From the wood stem and stem bark of the Panamanian plant Rondeletia panamensis (Rubiaceae), three novel diterpenes have been isolated. The structure of oxidopanamensin (2) was determined by single crystal X-ray crystallography of the diacetate derivative. Panamensin (4) was correlated with oxidopanamensin (2) by epoxidation under alkali conditions and with rondeletin (6) by hydrogenation to 14,15-dihydrorondeletin (8). Of the three isolates, panamensin (4) and oxidopanamensin (2) were cytotoxic in the KB test system but rondeletin was inactive.

X-ray diffraction studies of 9-methylanthracene and 5-methylnaphthacene

The crystal structures of 9-methylanthracene (I) and 5- methylnaphthacene (II) have been elucidated by direct methods, with adjustment of pseudohomometric variants on E maps. Both compounds crystallize in the 0567-7408/79/020404-07501.00

Metal complexes of novel sulphur- and phosphorus-containing heterocycles. Preparation and structure of tricarbonyl-η4-(1-pentafluorophenyl-2,3,4,5,-tetrakistrifluoromethylthiophen)manganese and π-Cyclopentadienyl(1-hydroxy-2,3,4,5,-tetrakistrifluoromethylphosphole 1-oxide)cobalt

Heterocyclic derivatives Mn(CO)3(C4F6)2SR and C5H5Co(C4F6)2PF3 are formed by reaction between hexafluorobut-2-yne and [Mn(CO)4SR]2, (R = CF3, C6F5), and (π-C5H5)Co(PF3)2; these derivatives contain non-planar heterocyclic rings with non-bonding metal heteroatom separations.

Metal–carbonyl and metal–nitrosyl complexes. Part XVI. Comparison of the molecular structures of dicarbonyl(π-cyclopentadienyl)[bis-(trifluoromethyl)phosphino]iron, [(π-C5H5)Fe(CO)2P(CF3)2], and its oxidation product, [(π-C5H5)Fe(CO)2P(:O)(CF3)2], as determined by X-ray crystallography

The molecular geometries of the complexes [(π-C5H5)Fe(CO)2P(CF3)2](1) and [(π-C6H6)Fe(CO)2P(:O)(CF3)2](2) have been determined by X-ray crystal-structure analysis. Mean P–C bond lengths [1·878(8) in (1), 1·887(6)A in (2)] demonstrate that the covalent radius of phosphorus is essentially the same in both complexes, but the difference in the Fe–P bond length [2·265(3) in (1), 2·191 (3)A in (2)] is interpreted in terms of increased Fe→P dπ–dπ back bonding in (2). The P–O bond length in (2) is 1·478(5)A. Both complexes crystallize in the monoclinic system, space group P21/c, with Z= 4; unit-cell dimensions are: (1), a= 8·602(7), b=11·924(9), c= 12·859(9)A, β= 112·75(9)°; (2), a= 11·938(8). b= 7·603(6), c= 13·818(9)A, β= 100·97(8)°. The crystal structures were elucidated by Fourier and full-matrix least-squares methods from diffractometer data. The analyses converged at R 4·8%[1882 reflections, (1)] and 4·5%[1777 reflections, (2)].

The twin-chair conformation of bicyclo[3.3.1]nonane. Differential distortions of the rings in 9-cyclohexylbicyclo[3.3.1]nonan-9-ol: an x-ray diffraction study

Abstract 9-Cyclohexylbicyclo[3.3.1]nonan-9-ol has a twin-chair conformation with C(3)...C(7) trans-annular separation of 3.134(3) A. In the twin chair, the ring carrying the 9-C6H11 group in the axial position is flattened to a greater extent than the ring with the 9-OH group axial. The crystals are monoclinic, space group P21/n. with a = 11.629(3), b =6.507(2), c = 17.122(3)A, β =93.80(2)°, and Z=4. The crystal structure was determined by direct phasing and the atomic co-ordinates were subsequently adjusted by least-squares calculations which converged at R = 0.047 for 1764 diffractometer ¦Fo¦values.

The twin-chair conformation of bicyclo[3.3.1]nonane: X-ray diffraction study of 5-methyl-1-p-toluenesulphonyloxymethylbicyclo[3.3.1]nonan-9-ol

CtaH2604S, triclinic, Pi, a = 7.377 (2), b = 11.303(3), c = 12.132 (2) A, a = 67.19(2), fl = 71.07 (2), ~, = 71.18 (2) ° , U = 859/~3, Z = 2, D c = 1.308 Mg m -3, F(000) = 364, /~(Mo Ka) = 0.21 mm -1. The structure was refined to R = 0.042 for 2224 reflections. The 1,5,9-trisubstituted bicyclo (3.3.1)- nonane has a twin-chair conformation with a C(3)...C(7) separation of 3.080 (4) /~,. Force-field calculations indicate that the substituents at C(1) and C(5) are responsible for the finding that the 3,7- separation is ca 0.03 /~ shorter than in the unsubsti- tuted hydrocarbon, bicyclo(3.3.1 )nonane.

Conformational control in the 3,7-diazbicyclo[3.3.1]nonane system

The twin-chair or boat-chair conformation of 3,7-diazabicyclo[3.3.1]nonaes can be selected by forming N,N′-derivatives in which the N atoms have planer or pyramidal bonding patterns, respectively, e.g. acyl substituents for the former and arylsulphonyl or alkyl for the latter.

X-Ray crystallographic determination of the molecular structures of π-cyclopentadienyl-[1-hydroxy-2,3,4,5-tetrakis(trifluoromethyl)phosphole-1-oxide]cobalt and tricarbonyl-η4-[1-pentafluorophenyl-2,3,4,5-tetrakis(trifluoromethyl)thiophen]manganese

The organometallic derivatives [Co(π-C5H5)(C4F6)2PO(OH)](1) and [Mn(CO)3(C4F6)2SC6F5](2) which resulted from the interaction of hexafluorobut-2-yne with metal complexes have been studied by X-ray diffraction and shown to contain non-planar (CF3)4C4X heterocycles with non-bonding metal–heteroatom separations. The absence of an Mn–S bond in (2) leads to the formulation of a zwitterion structure formally involving a sulphonium derivative with a Mn(–1) species. Crystals of (1) are orthorhombic with a= 9·353(7), b= 9·893(7), c= 17·923(10)A, space group P212121, and Z= 4. Crystals of (2) are triclinic with a= 7·889(6), 6=11·737(8), c= 12·195(9)A, α= 91·45(10), β= 69·71(10), γ= 81·55(9)°, space group P and Z= 2. Intensity data were collected on a four-circle diffractometer, and the structures solved by Fourier methods; least-squares refinements converged at R 6·3% over 1922 reflections for (1) and 4·5% over 3229 reflections for (2).