Access to the Parent Tetrakis(pyridine)gold(III) Trication, Facile Formation of Rare Au(III) Terminal Hydroxides, and Preliminary Studies of Biological Properties.

In this paper we report on the use of [NO][BF4] to access tricationic tetrakis(pyridine)gold(III) from Au powder, a species inaccessible using the more traditional (tetrahydrothiophene)AuCl route. It is then demonstrated that this family of compounds can be used to access new terminal Au(III) hydroxides, a challenging class of compounds, and the first crystallographically characterized examples employing bidentate ligands. Finally, preliminary biological studies indicate good activity for derivatives featuring polydentate ligands against the HeLa and PC3 cell lines but also strong inhibition of primary HUVEC cells.

Facile formation of homoleptic Au(III) trications via simultaneous oxidation and ligand delivery from [PhI(pyridine)2](2+).

We report the first examples of Au(III) tricationic complexes bound only by neutral monodentate ligands, which are a new class of gold reagents. Oxidative addition to the bis-pyridine Au(I) cation, [Au(4-DMAP)2](+), using a series of dicationic I(III) oxidants of the general form [PhI(L)2](2+) (L = pyridine, 4-DMAP, 4-cyanopyridine) allows ready access to homoleptic and pseudo-homoleptic Au(III) complexes [Au(4-DMAP)2(L)2](3+). The facile oxidative addition of Au(I) species additionally demonstrates the efficacy of PhI(L)2](2+) reagents as halide-free oxidants for Au(I). Comparisons are made via attempts to oxidize NHC-Au(I)Cl, where introduction of the chloride anion results in complex mixtures via ligand and chloride exchange, demonstrating the advantage of using the pyridine-based homoleptic compounds. The new Au(III) trications show intriguing reactivity with water, yielding dinuclear oxo-bridged and rare terminal Au(III)-OH complexes.

Reactions of [PhI(pyridine)2]2+ with model Pd and Pt II/IV redox couples.

The results of the reactions of the dicationic iodine(III) family of oxidants [PhI(pyridine)2](2+) with model Pd(II) and Pt(II) complexes are described. Depending on the specific reaction pairs, a variety of outcomes are observed. For palladium, Pd(IV) complexes cannot be observed but are implicated in C-C and C-N bond formation for Pd(II) starting materials based on phenylpyridine and 2,2-bipyridine, respectively. Theoretical comparisons with similar processes for -Cl and -OAc rather than pyridine indicate that these provide greater thermodynamic stability, and our results here show that they also give greater kinetic stability (the failure of MP2 methods for these systems is quite dramatic). In contrast, oxidation and delivery of the pyridine ligands gives dicationic Pt(IV) complexes that may be isolated and structurally characterized.

Well defined difluorogold(iii) complexes supported by N-ligands.

Stable difluorogold(iii) complexes can be easily synthesized either via oxidation of N-ligated cationic Au(i) precursors using XeF2 or from tricationic Au(iii) precursors by displacement of the N-ligands using fluoride from economical KF. X-ray crystallographic studies of the bisimidazole ligated derivative shows the shortest Au-F bond known in a gold complex.

A simple halide and silver-free synthesis of Echavarren's catalyst directly from gold powder.

An expedient procedure is reported for the preparation of the synthetically valuable Au(i) complex [Au(MeCN)(PtBu2C6H4Ph-2)][BF4] (Echavarren's catalyst) directly from gold powder using [NO][BF4] in acetonitrile. The synthetic method obviates the potential presence of silver or halide impurities that follow from the tedious conventional synthesis, and have otherwise been shown to moderate catalyst performance.

Direct formation of Au(iii) acetyl, alkoxyl and alkynyl functionalities via halide free tricationic Au(iii) precursors.

A novel synthetic approach for the synthesis of gold(iii) acetato, alkoxolato and alkynyl complexes was developed via the reactivity of gold(iii) trications containing the N,N-chelating ligand 2,2'-bipyridine and N,N,N-chelating ligand terpyridine through direct reactions with the protic precursors. This protocol avoids the gold(iii) chloride bond activation pathway commonly employed to access these functionalities. For example exposure of [LAu(iii)L']OTf3 (L = N,N,N-terpyridine, L' = 4-DMAP) to RH (R = OCH3, OAc, Ph-[triple bond, length as m-dash]) results in the facile formation of the corresponding functionalised gold(iii) complexes [LAu(iii)R]OTf2.

A 2,2'-bipyridine coordination complex of [ICl2]⁺.

The formation of a new class of I(III) compound is reported; an N,N' chelated iodine cation ([bpy-ICl2](+); bpy = 2,2'-bipyridine). The complex is obtained as an [ICl4](-) salt and is formed via simple reaction of bpy with ICl3. The compound is relatively unstable, but may be stored as a solid and is shown to be competent in the oxidative chlorination of Au(I)-NHC complexes.

The first bismuth-NHC complexes.

The synthesis, isolation and crystallographic characterization of the first N-heterocyclic carbene adducts of bismuth is reported, by direct reaction of the Dipp2NHC (Dipp = 2,6-diisopropylphenyl) or (i)Pr2(Me2)NHC with BiCl3. This represents the last non-radioactive element from groups 13-17 for which an NHC-element fragment remained unreported.