A square planar gold(iii) bis-(1,1'-dimethyl-3,3'-methylene-diimidazol-2,2'-diylidene) trication as an efficient and selective receptor towards halogen anions: the cooperative effect of AuX and XHC interactions.

Treatment of the tricationic gold(iii) [Au(MeImCH2ImMe)2](PF6)3 complex 1-3PF6 (Im = imidazol-2-ylidene) with excess halides affords complexes 1-3X (X = Cl, Br, and I), resulting from counter anion PF6-/X- exchange. The 1H chemical shift of the CH3 groups and particularly that of the CH2 linker in DMSO-d6 are different in the three complexes, thus suggesting selective XHC interactions. Complex 13+ can therefore be used as a halide sensor in DMSO and water. The host-guest interaction between the tricationic gold(iii) complex and the halides Cl-, Br- and I- in solution and in the solid state has been investigated by means of NMR titration experiments, DFT calculations and X-ray structure analysis. The electrostatic interaction between the halides and the triple formal positive charge on the metal centre, together with the CHX hydrogen bonding between the NHC ligand and halides, contributes to the formation of stable supramolecular aggregates in solution and in the solid state. The complexing properties of 13+ are strongly influenced by the nature of the solvent. Formation of the 1 : 1 and 1 : 2 species (1X2+ and 1X2+) is observed in DMSO-d6, while that of only the 1 : 1 aggregates (1X2+) is observed in D2O (X = Cl, Br, and I). Moreover, the selectivity towards the various halides is reversed in the two solvents, being in the order Cl- > Br- > I- in DMSO-d6 and I- > Br- > Cl- in D2O. The formation constants of the species 1X2+ and 1X2+ in DMSO and 1X2+ in water have been determined by fitting the NMR titration curves.

Insights into the Halogen Oxidative Addition Reaction to Dinuclear Gold(I) Di(NHC) Complexes.

Gold(I) dicarbene complexes [Au2 (MeIm-Y-ImMe)2 ](PF6 )2 (Y=CH2 (1), (CH2 )2 (2), (CH2 )4 (4), MeIm=1-methylimidazol-2-ylidene) react with iodine to give the mixed-valence complex [Au(MeIm-CH2 -ImMe)2 AuI2 ](PF6 )2 (1 a(I) ) and the gold(III) complexes [Au2 I4 (MeIm-Y-ImMe)2 ](PF6 )2 (2 c(I) and 4 c(I) ). Reaction of complexes 1 and 2 with an excess of ICl allows the isolation of the tetrachloro gold(III) complexes [Au2 Cl4 (MeIm-CH2 -ImMe)2 ](PF6 )2 (1 c(Cl) ) and [Au2 Cl4 (MeIm-(CH2 )2 -ImMe)2 ](Cl)2 (2 c(Cl) -Cl) (as main product); remarkably in the case of complex 2, the X-ray molecular structure of the crystals also shows the presence of I-Au-Cl mixed-sphere coordination. The same type of coordination has been observed in the main product of the reaction of complexes 3 or 4 with ICl. The study of the reactivity towards the oxidative addition of halogens to a large series of dinuclear bis(dicarbene) gold(I) complexes has been extended and reviewed. The complexes react with Cl2 , Br2 and I2 to give the successive formation of the mixed-valence gold(I)/gold(III) n a(X) and gold(III) n c(X) (excluding compound 1 c(I) ) complexes. However, complex 3 affords with Cl2 and Br2 the gold(II) complex 3 b(X) [Au2 X2 (MeIm-(CH2 )3 -ImMe)2 ](PF6 )2 (X=Cl, Br), which is the predominant species over compound 3 c(X) even in the presence of free halogen. The observed different relative stabilities of the oxidised complexes of compounds 1 and 3 have also been confirmed by DFT calculations.

Metal complexes with di(N-heterocyclic carbene) ligands bearing a rigid ortho-, meta or para-phenylene bridge.

Three novel dinuclear bis-dicarbene silver(i) complexes of general formula [Ag2(MeIm-phenylene-MeIm)2](PF6)2 (Im = imidazol-2-ylidene) were synthesized. The corresponding copper(i) and gold(i) complexes were obtained by transmetalation of the di(N-heterocyclic carbene) ligand from the silver(i) species, and both coordination geometry and stoichiometry are maintained for all three group 11 metals as expected. The photophysical properties of the Ag(i) and Au(i) complexes were also investigated and discussed; in particular the most strongly emitting complex was also studied via DFT calculations. In addition, the ruthenium(ii) and iridium(iii) complexes [RuCl(MeIm-(o-phenylene)-MeIm)(p-cym)](PF6) and [IrClCp*(MeIm-(o-phenylene)-MeIm)](PF6) were prepared and shown to present in these cases a chelating coordination of the di(N-heterocyclic carbene) ligand.

Synthesis and biological assays on cancer cells of dinuclear gold complexes with novel functionalised di(N-heterocyclic carbene) ligands.

New dinuclear di(N-heterocyclic carbene) silver(I), gold(I) and gold(III) complexes have been synthesised and their antiproliferative effects towards various cancer cell lines have been screened. The di(N-heterocyclic carbene) ligands have a propylene linker between the carbene moieties and the imidazole backbone has been functionalised with a 1-benzyl- or 1-PEG-1,2,3-triazole ring (PEG=poly(ethylene glycol)) via a CuAAC (copper azido alkyne cycloaddition) reaction. The resulting gold(I) and gold(III) complexes display an antiproliferative activity superior to that of the unfunctionalised pristine complexes together with a higher selectivity towards cancerous cells with respect to healthy cells.

Dinuclear gold(I) complexes with propylene bridged N-heterocyclic dicarbene ligands: synthesis, structures, and trends in reactivities and properties.

Four novel dinuclear N-heterocyclic dicarbene gold(I) complexes with a propylene linker between the carbene moieties have been synthesized and their luminescence and electrochemical properties, together with their reactivity towards bromine oxidative addition, have been screened. All the complexes emit in the solid state in the blue-green spectral range (400-500 nm) with appreciable intensities (Φ(em) up to ≈10%). In cyclic voltammetry, the Au(I)/Au(0) peak splits at low temperature into two separate peaks relative to the couples Au(I)-Au(I)/Au(I)-Au(0) and Au(I)-Au(0)/Au(0)-Au(0), thus indicating the presence of an Au···Au interaction in the dinuclear complex. Oxidative addition of bromine affords as a major or unique product Au(II)-Au(II) complexes most likely as a consequence of the interaction between the two gold centres favoured by the propylene linker.

Alkyne hydroarylation with Au N-heterocyclic carbene catalysts.

Mono- and dinuclear gold complexes with N-heterocyclic carbene (NHC) ligands have been employed as catalysts in the intermolecular hydroarylation of alkynes with simple unfunctionalised arenes. Both mono- and dinuclear gold(III) complexes were able to catalyze the reaction; however, the best results were obtained with the mononuclear gold(I) complex IPrAuCl. This complex, activated with one equivalent of silver tetrafluoroborate, exhibited under acidic conditions at room temperature much higher catalytic activity and selectivity compared to more commonly employed palladium(II) catalysts. Moreover, the complex was active, albeit to a minor extent, even under neutral conditions, and exhibited lower activity but higher selectivity compared to the previously published complex AuCl(PPh(3)). Preliminary results on intramolecular hydroarylations using this catalytic system indicate, however, that alkyne hydration by traces of water may become a serious competing reaction.

Blue-emitting dinuclear N-heterocyclic dicarbene gold(I) complex featuring a nearly unit quantum yield.

Dinuclear N-heterocyclic dicarbene gold(I) complexes of general formula [Au(2)(RIm-Y-ImR)(2)](PF(6))(2) (R = Me, Cy; Y = (CH(2))(1-4), o-xylylene, m-xylylene) have been synthesized and screened for their luminescence properties. All the complexes are weakly emissive in solution whereas in the solid state some of them show significant luminescence intensities. In particular, crystals or powders of the complex with R = Me, Y = (CH(2))(3) exhibit an intense blue emission (λ(max) = 450 nm) with a high quantum yield (Φ(em) = 0.96). The X-ray crystal structure of this complex is characterized by a rather short intramolecular Au···Au distance (3.272 Ǻ). Time dependent density functional theory (TDDFT) calculations have been used to calculate the UV/vis properties of the ground state as well as of the first excited state of the complex, the latter featuring a significantly shorter Au···Au distance.

Alkyne hydroarylation in ionic liquids catalyzed by palladium(II) complexes.

The efficiency of dicarbene palladium(II) complexes and of simple palladium(II) acetate as catalysts for alkyne hydroarylation under liquid-liquid biphasic conditions involving an ionic liquid as the catalyst-containing phase is investigated. The results obtained under these conditions, both in terms of activity and selectivity, are compared with those previously obtained under homogeneous conditions. The catalytic efficiency of the systems is found to be markedly dependent on the nature of the anion of the ionic liquid. Suitable anions are found to significantly improve the catalytic performance in comparison to homogeneous conditions. Preliminary investigations on the recyclability of the system as well as the on advantages of using an acidic ionic liquid are also carried out.

Cisplatin and oxaliplatin cytotoxic effects in sensitive and cisplatin-resistant human cervical tumor cells: time and mode of application dependency.

BACKGROUND: Time-dependence of cisplatin (CDDP) and oxaliplatin (L-OHP) cytotoxic effects in A431 and A431/Pt cells (sensitive and CDDP-resistant human cervical tumor cells) were investigated. MATERIALS AND METHODS: The drug application modes were pulse (12.5, 25 or 50 microM up to 72 h) and pulse-plus-chase (50 microM for 2, 4 or 6 h, followed by washing and 72 h-incubation in drug-free medium). RESULTS: In the A431 cells, the pulse drug application showed time-effect curves with two plateaux; the inhibitory activity of CDDP was higher than that of L-OHP. The same growth-inhibition fraction was reached by L-OHP in a longer time than CDDP. In the A431/Pt cells, the curve shapes for both drugs were similar in both application modes and had the same general characteristics, noted in the parental cell line. CDDP appeared less active than L-OHP. CONCLUSION: Different cytotoxicity curves of Pt-drugs could be dictated by the presence of the bulky diaminocyclohexane (DACH) ligand, affecting the kinetics of Pt-DNA binding; mismatch repair (MSH2) protein is involved in the resistance.

Reactions of diazo compounds with alkenes catalysed by [RuCl(cod)(Cp)]: effect of the substituents in the formation of cyclopropanation or metathesis products.

The reaction of diazo compounds with alkenes catalysed by complex [RuCl(cod)(Cp)] (cod = 1,5-cyclooctadiene, Cp = cyclopentadienyl) has been studied. The catalytic cycle involves in the first step the decomposition of the diazo derivative to afford the reactive [RuCl(Cp){=C(R(1))R(2)}] intermediate and a mechanism is proposed for this step based on a kinetic study of the simple coupling reaction of ethyl diazoacetate. The evolution of the Ru-carbene intermediate in the presence of alkenes depends on the nature of the substituents at both the diazo N(2)=C(R(1))R(2) (R(1), R(2) = Ph, H; Ph, CO(2)Me; Ph, Ph; C(R(1))R(2) = fluorene) and the olefin substrates R(3)(H)C=C(H)R(4) (R(3), R(4) = CO(2)Et, CO(2)Et; Ph, Ph; Ph, Me; Ph, H; Me, Br; Me, CN; Ph, CN; H, CN; CN, CN). A remarkable reactivity of the complex was recorded, especially towards unstable aryldiazo compounds and electron-poor olefins. The results obtained indicate that either cyclopropanation or metathesis products can be formed: the first products are favoured by the presence of a cyano substituent at the double bond and the second ones by a phenyl.

Trinuclear copper(I) complexes with triscarbene ligands: catalysis of C-N and C-C coupling reactions.

Novel synthetic routes for the preparation of trinuclear copper(I) complexes with triscarbene ligands are presented, which yield higher purity products than the one previously described. The first crystal structure of one of these complexes is reported and confirms the expected structure. The trinuclear complexes proved to be efficient catalysts of Ullmann-type reactions as well as of the Sonogashira reaction.

A fluorous chiral dirhodium(II) complex as a recyclable asymmetric catalyst.

[reaction: see text] The chiral fluorous complex tetrakis-dirhodium(II)-(S)-N-(n-perfluorooctylsulfonyl)prolinate has been prepared and used as a catalyst in homogeneous or fluorous biphasic fashion. The catalyst displays good chemo- and enantioselectivity in intermolecular cyclopropanation and C-H bond activation reactions. The catalyst can be simply and thoroughly separated from the reaction mixture and is recyclable.

Nucleophilic substitution on a Ru-coordinated Cp ring by a carborane anion.

The Cp ring in [RuCl(Cp)(PPh3)2] undergoes an apparent nucleophilic attack by the carbanion carb- (Hcarb = 2-Me-1,2-dicarba-closo-dodecaborane), to give an H-/carb- exchange process, which is favoured by coordination of the hydride to the ruthenium centre.

Synthesis of beta-Imino Carbonyl Enolato Complexes by Reaction of Nickel(II), Palladium(II), and Copper(II) Acetates with the Enaminodiones (MeOCO)(RCO)CC(R')NH(2) (R = Me, OMe; R' = Et, EtOCO).

Nickel(II), palladium(II), and copper(II) acetates undertake exchange reaction with the beta-enaminodiones (MeOCO)(RCO)CC(R')NH(2) (R = Me, OMe; R' = Et, EtOCO) in ethanol to give the neutral complexes [M((MeOCO)(RCO)CC(R')NH)(2)] (1-8) [R = Me, R' = Et: M = Ni (1), Pd (2a,b), Cu (3); R = Me, R' = EtOCO: M = Ni (4), Pd (5), Cu (6); R = MeO, R' = Et, M = Pd (7a,b); R = MeO, R' = EtOCO, M = Pd (8a,b)]. The trifunctional N,O,O ligands act in all cases as bidentate through the imino and one carbonyl group. Complexes 1-8 are all monomers with a square planar geometry. Nickel and palladium complexes show more than one form in the solid state. For example the palladium complex 2 has been synthesized in two forms a and b, which differ in the conformation of the methoxy carbonyl substituent of the chelate ring, while the third isomer or conformer is obtained by thermal treatment at 120 degrees C. Complexes 7 and 8 also exhibit two forms which differ in the degree of intermolecular hydrogen bonding. Both 7b and 8b crystallize in monoclinic unit cells [7b: space group P2(1)/n, a = 11.963(2), b = 8.438(1), c = 19.637(2) Å, beta = 94.2(1) degrees. 8b: P2(1)/c, a = 10.698(2), b = 14.902(2), c = 13.918(2) Å, beta = 95.2(1) degrees ] containing four molecules linked by intermolecular hydrogen bonding [N-H.O=C, 2.14-2.36 Å]. All complexes are thermally stable and volatile. Their mass spectra exhibit intense molecular ion peaks under EI mass conditions.