David S. Brown

Epoxidation with dioxiranes derived from 2-fluoro-2-substituted-1-tetralones and -1-indanones

Abstract Homochiral 2-fluoro-2-substituted-1-tetralones ( 10a , 10b , 13 ) and ethyl 2-fluoro-1-indanone-2-carboxylate ( 16 ) have been isolated. The dioxirane derivatives of these ketones have been prepared in situ , and have been shown to epoxidise alkenes but not enantioselectively. The dioxirane derivative of methyl 2,5,7-trifluoro-1-indanone-2-carboxylate ( 18 ) has been shown to be comparatively efficient in epoxidation.

A reinvestigation of o-phenylenemercurials : IV. Adducts of perfluorotribenzo[b,e,b][1,4,7]trimercuronin and the crystal and molecular structure of its 1 : 1 4-phenylpyridine solvate

Abstract Perfluorotribenzo[b,e,h][1,4,7]trimercuronin forms adducts of 1 : 1, 1 : 2 and 1 : 3 stoicheiometry with a variety of polar organic molecules. The structure of the 1 : 1 adduct with 4-phenylpyridine was solved by X-ray methods to an R factor of 7.4% for 3528 observed reflections.

The crystal and molecular structures of bis (pentafluorophenyl)disulphide and bis(pentafluorophenyl)diselenide

Abstract The structures of (C 6 F 5 ) 2 S 2 and (C 6 F 5 ) 2 Se 2 have been determined by single crystal, X-ray diffraction techniques. The compounds are isostructural although the molecules are packed differently in the crystal in comparison with their phenyl analogues. Important bond lengths and angles are: SS, 2.059(4)A; SeSe, 2.319(4)A; SC, 1.770A; SeC, 1.910(15)A; SSC, 101.3(3)°; SeSeC, 98.8(1)°.

Chiral oximes in asymmetric synthesis. Addition of organometallic reagents to o-(1-phenylethyl) aldoximes

Abstract Addition of Grignard and organolithium reagents to O -(1-phcnylethyl) aldoximes in the presence of boron trifluoride etherate gives secondary hydroxylamines in 21–84% yield with up to 95% diastercomeric excess.

Radical reactions of bicyclo[2.2.1]heptan-3-spiro-2′-oxiranes

Abstract Tributyltin hydride reduction of 2-bromo- and 2-keto-bicyclo[2.2.1]heptan-3-spiro-2′-oxiranes gives ring opening of the oxirane-rings via intermediate 3-(spiro-2′-oxiranyl)bicyclo[2.2.1]heptan-2-yl radicals, whereas reduction of the analogous 2-(thiocarbonyl)imidazolides) [2-(O-CS-Im)] unusually yields the 2-methoxy derivatives and does not proceed by the expected normal fragmentation to yield 3-(spiro-2′-oxiranyl)bicyclo[2.2.1]heptan-2-yl radicals and subsequent ring-opening of the oxirane rings.

The crystal and molecular structure of bis(2,3,4,5-tetrafluorophenyl)mercury ☆

Abstract During studies on the preparation of perfluoro- o -phenylenemercury, bis- (2,3,4,5-tetrafluorophenyl) mercury was isolated as a by-product and characterised by spectroscopic and X-ray techniques.

A reinvestigation of phenylene- and polyphenylene-mercurials

Abstract Evidence is presented to show that ortho-phenylenemercury is a trimer; no evidence was obtained for the previously reported hexameric form. Similarly, ortho-biphenylenemercury and its perfluoro-analogue exist as trimers and not tetramers, while ortho-terphenylenemercury is a dimer.

Structure of the tetra-n-butylammonium salt of the tetrachloro(methanol)nitrosyltechnetium(II) anion

C4Hg)4N)(Tc(NO )CI4(CHaOH)), M r = 545.3, monoclinie, P2~/n, a= 11.350 (10), b= 11.450(5), c=22.154(10)A, fl=91.5(2) °, u =2878.85A 3, Z=4, D m not measured, Dx= 1.256 g cm -3, 2(Mo Ktx) = 0.7107 A, :t = 8.0 cm -~, F(000) -- 932, T= 293 K, R = 0.051 for 2282 ob- served reflexions with I > 3tr(I). The anion (Tc(NO)- C14(CH3OH))- has a distorted octahedral geometry with the four C1 atoms lying in an equatorial plane and the other two ligands axial. The nitrosyl group is bonded almost linearly to the Tc and the coordinated methanol trans to it was found to be hydrogen-bonded to a methanol of solvation. Introduction. The use of technetium-99m in the field of nuclear medicine is well established; technetium-99 enables extensive research into the coordination chemis- try of the element. We are interested, in particular, in the synthesis of technetium complexes as possible radiopharmaceuticals in which the Tc atom is in a low oxidation state. The exact structure of the (Tc(NO)X4_5) ~-°r2- com- plexes has been a matter of discussion. The ESR data

A convenient method for the analysis of organometallic and related compounds

Abstract X-ray spectrometry of small amounts of compounds presented as pressed discs in borax is shown to be a convenient method for analysis, and is especially suitable for compounds which are not amenable to conventional combustion analyses.

The synthesis and characterisation of the trichloronitrosyl(acetylacetonato)technetium(II) anion, a novel technetium(II) complex

The reaction of [TcNOCL4]− with acetylacetone was found to give the complex [TcNO(acac)Cl3]−. This complex has been fully characterised by X-ray crystallography and FAB− Mass spectrometry. The former shows that one of the oxygens of the acac is trans to the nirtosyl which is essentially linear, although disorder in the crystal prohibits accurate measurements of the bond angle. The latter shows facile loss of a single chlorine which suggests that ligand exchange of this may be facile. The ESR spectrum at room temperature shows the expected 10 lines due to splitting by the technetium. At −196°C the spectrum may be modelled as having three g values,gx = 2.0107,gy = 2.02225 and gz = 1.9460.