Andrew R. Cowley

Catalytic Enantioselective Intermolecular Hydroacylation : Rhodium-Catalyzed Combination of β-S-Aldehydes and 1,3.Disubstituted Allenes

A rhodium(I) catalyst incorporating the Me-DuPhos ligand promotes enantioselective intermolecular hydroacylation between beta-S-aldehydes and 1,3-disubstituted allenes. The nonconjugated enone products are obtained in good yields and with high enantioselectivities.

Structural trends in copper(II) bis(thiosemicarbazone) radiopharmaceuticals

Redox-related changes in biological properties of copper bis(thiosemicarbazone) radiopharmaceuticals are induced by backbone alkylation. To determine whether these changes are mediated by changes in core structural parameters, eight X-ray structures of variously alkylated complexes were determined. The complexes include the hypoxia tracer diacetylbis(4-methyl-3-thiosemicarbazonato)copper(II) (CuATSM). The structures of the nickel analogue NiATSM and the corresponding free ligand ATSMH2 were also included. Distortions from planarity were slight and only present when there were significant intermolecular interactions (mainly pairs of N–H–N and N–H–S hydrogen bonds). These give rise to cross-linked flat or helical ribbons of complexes. Alkylation at the terminal nitrogen atoms interrupts hydrogen bonding, allowing complexes to become planar, but does not otherwise affect the coordination sphere. Alkylation at the backbone carbon atoms increases the backbone C–C bond length, allowing the metal to fit better into the ligand cavity with shorter Cu–S bonds.

Tetrakis(imidazolium) macrocyclic receptors for anion binding

New (tetrakis)imidazolium macrocyclic receptor systems of variable cavity size have been synthesised by stepwise alkylation reactions of bis(imidazolium) precursor compounds. Proton NMR titration studies reveal the macrocycles to strongly bind halide and benzoate anions, with two receptor systems displaying notable selectivity for fluoride in competitive acetonitrile-water (9:1) solvent media.

Silver(I) complex of a new imino-N-heterocyclic carbene and ligand transfer to palladium(II) and rhodium(I)

A new imino-N-heterocyclic carbene ligand precursor [1-(2,4,6-Me3C6H2)imidazolium-3-{CH2C(t-Bu)N(i-Pr)}] bromide has been synthesised and structurally characterised. The silver(I) complex [Ag(C⁁imine)2]AgBr2, where (C⁁imine) = 1-(2,4,6-Me3C6H2)imidazol-2-ylidene-3-{CH2C(t-Bu)N(i-Pr)}, was readily prepared by reaction with Ag2O. Transfer of the ligand from silver(I) to palladium(II) and rhodium(I) by reaction with [PdCl2(MeCN)2] and [Rh(cod)(THF)2][BF4] led to the tautomerisation of the imine moiety to the enamine affording the structurally characterised complex [PdCl2(C⁁enamine)] and [Rh(cod)(C⁁enamine)][BF4] respectively, where (C⁁enamine) = 1-(2,4,6-Me3C6H2)imidazol-2-ylidene-3-{CHC(t-Bu)NH(i-Pr)}.

Monomeric, two-coordinate Mn, Fe and Co(II) complexes featuring 2,6-(2,4,6-trimethylphenyl)phenyl ligands.

The synthesis and characterization of the monomeric, two-coordinate transition-metal complexes (2,6-Mes(2)C(6)H(3))(2)M (Mes = mesityl, 2,4,6-Me(3)C(6)H(2), M = Mn, Fe, Co) are reported; (2,6-Mes(2)C(6)H(3))(2)Co is the first structurally authenticated two-coordinate, homoleptic cobalt(II) complex featuring sigma-bonded aryl ligands.

Indolocarbazoles: a new family of anion sensors

Simple preorganised indolo[2,3-a]carbazole derivatives are shown to recognise and sense anionic guest species using fluorescence spectroscopy.

A remarkable inversion of structure–activity dependence on imido N-substituents with varying co-ligand topology and the synthesis of a new borate-free zwitterionic polymerisation catalyst

Ethylene polymerisation productivities of tris(pyrazolyl)methane-supported catalysts [Ti(NR){HC(Me2pz)3}Cl2] show a dramatically different dependence on the imido R-group compared to those of their TACN analogues, attributed to differences in fac-N3 donor topology; when treated with AliBu3, the zwitterionic tris(pyrazolyl)methide compound [Ti(N-2-C6H4tBu){C(Me2pz)3}Cl(THF)] also acts as a highly active, single site catalyst (TACN = 1,4,7-trimethyltriazacyclononane).

CoGaPO-5: Synthesis and crystal structure of (C6N2H14)2[Co4Ga5P9O36], a microporous cobalt-gallium phosphate with a novel framework topology

A microporous cobalt-gallium phosphate, (C6H14N2)2[Co4Ga5P9O36], has been synthesized under solvothermal conditions and the structure determined at 293 K by single-crystal X-ray diffraction (monoclinic, I 2/a, a = 15.002(2), b= 17.688(2), c= 15.751(2) A, β = 97.24(1)∘, V= 4146.3 A3, Z= 4). The framework of this material is constructed from alternately linked MO4 (M = Co or Ga) and PO4 tetrahedra, and it has a topology unlike that of any previously reported material. The DABCO template occupies sites within 2-dimensional intersecting networks of pores, which are surrounded by 8- and 10-membered rings. The structure has been approved by the Structure Commission of the International Zeolite Association and given the code CGF.

Bifunctional dithiocarbamates: a bridge between coordination chemistry and nanoscale materials

A dithiocarbamate-based methodology is employed to prepare linked heteromultimetallic complexes and then further exploited in the surface functionalisation of gold nanoparticles.

A novel transformation of a zirconium imido compound and the development of a new class of N3 donor heteroscorpionate ligand

Reaction of the dimeric zirconium imido compound [Zr2(mu-NAr)2Cl4(THF)4] with tris(3,5-dimethylpyrazolyl)methyl silane very selectively gave [Zr{(Me2pz)2Si(Me)NAr}Cl3] (1), a highly active pre-catalyst for ethylene polymerisation; a more general and versatile route to N3 donor heteroscorpionate compounds was achieved via the protio ligand (Me2pz)2CHSi(Me)2N(H)iPr for which neutral and cationic organometallic Group 3 and 4 derivatives are reported (Ar = 2,6-C6H(3)iPr2).