Alan Hazell

Dinuclear and tetranuclear iron(III) complexes containing the μ-oxo-di-μ-acetato motif

Abstract A series of μ-oxo-di-μ-acetato-bridged diiron(III) and tetrairon(III) complexes are reported. The remainder of the Fe coordination spheres are occupied by the ligands N-methyl-bis(2-pyridylmethyl)amine (medpa), N-methyl-N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,2-ethanediamine (metpen+), N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,3-propanediamine (tptn) and N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,4-butanediamine (tpbn). The crystal structures of two new μ-oxo-di-μ-acetato-brigded diiron(III) complexes, [Fe2medpa2(CH3CO2)2O]-(ClO4·2H2O (1) and [Fe2metpen2(CH3CO2)2O](ClO4)4·7H2O (2) have been determined. They have identical core characteristics to a tetranuclear iron(III) reported in an earlier communication. Complex 1 crystallizes in the monoclinic space group P21/c, with a = 10.753(3), b = 23.990(3), c = 16.291(1) A , β = 108.40(1) and Z = 4 . The structure refined to a final R value of 0.101 for 4050 reflections. The Fe atoms are bridged by a μ-oxo group and two acetate groups with Fe-μ-O, 1.816(9), 1.76(1) A; FeOFe, 118.2(4)°; and Fe…Fe 3.068(3) A. Complex 2, which contains an unusual positively-charged ligand crystallizes in the orthorhombic space group Cmcm, with a = 15.895(4), b = 29.754(9), c = 16.254(5) A and Z = 4 . The structure refined to afinal R value of 0.066 for 1399 reflections. The Fe atoms are bridged by a μ-oxo group and two acetate groups with Fe-μ-O, 1.800(6) A; FeOFe, 116.4°; and Fe…Fe 3.059(4) A. By contrast, the complexes of tptn and tpbn form tetranuclear complexes with the propane and butane backbones ‘strapping’ between two [FeO(CH3CO2)2Fe] cores.

Synthesis, structural characterisation and electronic behaviour of iron(II) and nickel(II) complexes of N,N-bis(2-pyridylmethyl)aniline

Abstract Ni(II) and Fe(II) complexes of the new ligand N,N-bis(2-pyridylmethyl)aniline (phdpa) of the general formula [M(phdpa)2](ClO4)2 have been prepared and characterised. [Ni(phdpa)2](ClO4)2·0.5 H2O was characterised by X-ray crystallography. For comparison, the X-ray structure of [Ni(medpa)2](ClO4)2 (where medpa is bis(2-pyridylmethyl)methylamine) has been determined. The ligand in both [Ni(phdpa)2](ClO4)2 and [Ni(medpa)2](ClO4)2 exhibit cis–facial geometry.

Syntheses, Structures, and Properties of Copper(II) Complexes of Bis(2-pyridylmethyl) Derivatives of o-, m-, and p-Phenylenediamine and Aniline

Copper(II) complexes of the ligand 1,n-bis[bis(2-pyridylmethyl)amino]benzene with n = 2-4 (1,n-tpbd) and its mononuclear derivative bis(2-pyridylmethyl)aniline (phbpa) were synthesized and structurally characterized. Magnetic measurements and DFT calculations were performed on [CuCl2(phbpa)], [Cu2Cl4(1,3-tpbd)], [(Cu2Cl2(ClO4)(1,3-tpbd))Cl(Cu2Cl2(OH2)(1,3-tpbd))](ClO4)2, and [Cu2(OH2)2(S2O6)(1,3-tpbd)]S2O6, and the exchange-polarization mechanism was successfully demonstrated.

Silyl nitronates and nitrile oxides in organic synthesis. A novel route to d,l-deoxysugars. Use of aluminum oxide as solid phase base for generation of

Abstract Novel methodology is developed for a three step synthesis of deoxyaldoses and deoxyketoses: 1. Regioselective addition of silyl nitronate or nitrile oxide to a diene. 2. Stereospecific hydroxylation of the double bond. 3. Unmasking of the aldol moiety by catalytic reduction of the 2-isoxazoline. The syntheses of D,L-deoxyribose, D,L-oleose, D,L-digitoxose, D,L-2-deoxygalactose, 1,3-dideoxyfructose, 3-deoxyfructose etc. are described. Basic aluminum oxide is introduced as a solid phase base for the one step synthesis of 2-isoxazolines from aldoximes and olefins. An X-ray diffraction study of compound 13c verifies the stereochemical assignments.

Divalent transition metal complexes of alkylpyridyl derivatized dmit ligands

Abstract The two new bis-alkylpyridyl substituted dmit ligands, 4,5-bis(2-pyridylmethylsulfanyl)-1,3-dithiole-2-thione (bpmdmit) and 4,5-bis(2-pyridylethylsulfanyl)-1,3-dithiole-2-thione (bpedmit), and some of their transition metal complexes have been prepared. Two basic structural types for the complexes MX2L (M=Ni, Co, Cu, Pd; L=bpmdmit or bpedmit; X=Cl or Br) were determined by X-ray crystallography. The cobalt(II) and the nickel(II) complexes CoBr2(bpmdmit) and NiCl2(bpmdmit) show octahedral geometries around the metal ions with coordination to the metal ions by the pyridyl nitrogen atoms and the thioether sulfur atoms of the ligand and cis coordination of the halide ions. By contrast, only the pyridyl nitrogen atom of the ligands in the copper(II) and the palladium(II) complexes, CuCl2(bpedmit) and PdCl2(bpedmit), are coordinated to the metal ions to give essentially square planar metal environments. The copper complex was isolated as both green and purple crystals. However, the X-ray structures of both forms are similar, and show a dimeric arrangement with bis-μ-chloride bridges between the copper ions in the dimeric units. The green crystals contain two molecules of acetonitrile in the unit cell, however these do not interact with the metal ions. The geometry of the copper ions in the green form deviates most from centrosymmetric square planar geometry and this is consistent with the observed colour. Apart from the colour, the solids can be distinguished in the solid state by EPR spectroscopy since they give different rhombic signals. UV–Vis and EPR spectroscopy show that in solution the structures of the purple and green forms of CuCl2(bpedmit) are identical, as expected.

Indole alkaloids and terpenoids from Tabernaemontana markgrafiana

Abstract The bark of Tabernaemontana markgrafiana yielded five acetylated pentacyclic triterpenes and 24 monoterpene indole alkaloids. The major triterpene

Mono- and di-bridged µ-oxo diiron complexes of 3-[bis(2-pyridylmethyl)amino]propionate (bpp). Crystal structures of [{Fe(bpp)(H2O)}2O][ClO4]2·H2O and [{Fe(bpp)}2(MeCO2)O][ClO4]·4.5H2O

Oxo-bridged dinuclear iron(III) complexes of the new tetradentate ligand, the conjugate base of 3-[bis(2-pyridylmethyl)amino]propionic acid (Hbpp), have been prepared. The structure of the monobridged µ-oxo-diiron(III) complex [{Fe(bpp)(H2O)}2O][ClO4]2·H2O 1 shows that the bpp is co-ordinated to each iron centre as a terminal capping ligand. A water molecule completes the co-ordination sphere of each iron atom. Complex 1 crystallizes in the triclinic space group P, with a= 13.260(4), b= 14.389(4), c= 11.347(3)A, α= 92.224(14), β= 113.722(13), γ= 97.719(17)° and Z= 2. The structure refined to a final R value of 0.077 for 4249 reflections. The Fe atoms are bridged by a single µ-oxo group with average Fe–O 1.790(4)A, Fe–O–Fe 168.8(3)° and Fe ⋯ Fe 3.564(2)A. The cations are linked by hydrogen bonds forming chains parallel to the b axis. The co-ordinated water molecules of 1 can be replaced easily by the two co-ordinating atoms of bidentate oxo anions to form dibridged complexes. µ-Oxo complexes containing supporting µ-acetato and µ-phosphato bridges were prepared in this fashion. These substitution reactions involve a contraction of the Fe–O–Fe angle. A structural characterization of the acetato-bridged complex, [{Fe(bpp)}2(MeCO2)O][ClO4]·4.5H2O 2, has been carried out and shows that the iron atoms are doubly-bridged by a µ-oxide atom and µ-acetato group, with average Fe–O 1.82(2)A, Fe–O–Fe 129(1)° and Fe ⋯ Fe 3.245(6)A. Complexes 1 and 2 show strong antiferromagnetic coupling, as is usually observed in oxo-bridged iron pairs; J=-114 and -110 cm–1 for 1 and 2 respectively.

Triterpenes, lichexanthone and an acetylenic acid from Minquartia guianensis

Abstract Lichexanthone, 17-hydroxy,9,11,13,15-octadecatetraynoic acid and fatty acid esters (mixture) of erythrodiol (12-oleanene-3,28-diol, 3-β-form), and betulin (20-(29)-lupen-3,28-diol) were isolated. The structure of the new triterpene, 13,28-epoxy-3-acetoxy-11-oleanene, 3β,13β form, was determined by X-ray diffraction. The triterpenes occur mainly as C-3-O-palmitates.

Synthesis and characterisation of complexes formed between the ligand tris(2-pyridylmethyl)amine and the Group III metals gallium and thallium

Reactions of the Group III metals, gallium and thallium, with the ligand tris(2-pyridylmethyl)amine (TPA) leads to the formation of 1:1 metal to ligand complexes, but not the simple 1:1 complexes observed in the reactions between the Group I and II metals with TPA. One such complex, [Ga(TPA)(OH)]2(Cl)4·4H2O·2.956MeOH (1), has been structurally characterised and found to have a dimeric structure resulting from hydroxy bridging. The crystal structure of the thallium complex was also determined and was found to be [Tl(TPA)]2[H3O][NO3]3 (2), consisting of two different [Tl(TPA)] + cations, one of which was disordered. The essential difference between the two cations is that one contains a four co-ordinate thallium cation while the second contains a seven co-ordinate thallium cation as a result of bonding to the three nitrate anions.

A lignan and pyrone and other constituents from Hyptis capitata

Abstract Investigation of the aerial parts of the medicinal plant Hyptis capitata led to the isolation of two new compounds: 2,3-di(3′,4′-methylenedioxybenzyl)-2-buten-4-olide, a lignan with a γ-butenolide structure and 10-epi-olguine, a 5,6-dihydro-α-pyrone. The structure of 10-epi-olguine was determined using X-ray diffraction. Also isolated were stigmasterol, 5-hydroxy-4′,7-dimethoxyflavone (apigenin-4′,7-dimethyl ether), oleanolic, ursolic and rosmarinic acids. The crude extracts prepared with petrol, dichloromethane and methanol showed no pronounced fungicidal or insecticidal eitects. The plant contains no alkaloids.