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Platinum(II) olefin compounds [PtMe(N,N′-imino, amide)(η2-olefin)] have been found to dimerize spontaneously in solution, yielding dinuclear complexes through an oxidative coupling. The extended conjugation within the molecules produces an intense blue color, and the properties of the compounds have been investigated through NMR spectroscopy, optical measurements, and theoretical calculations. The solid-state structure of a representative compound has been solved.

This study describes new platinum(II) cationic five-coordinate complexes (1-R,R’) of the formula [PtR(NHC)(dmphen)(ethene)]CF3SO3 (dmphen = 2,9-dimethyl-1,10-phenanthroline), containing in their axial positions an alkyl group R (methyl or octyl) and an imidazole-based NHC-carbene ligand with a substituent R’ of variable length (methyl or octyl) on one nitrogen atom. The Pt–carbene bond is stable both in DMSO and in aqueous solvents. In DMSO, a gradual substitution of dmphen and ethene is observed, with the formation of a square planar solvated species. Octanol/water partitioning studies have revealed the order of hydrophobicity of the complexes (1-Oct,Me > 1-Oct,Oct > 1-Me,Oct > 1-Me,Me). Their biological activity was investigated against two pairs of cancer and non-cancer cell lines. The tested drugs were internalized in cancer cells and able to activate the apoptotic pathway. The reactivity of 1-Me,Me with DNA and protein model systems was also studied using UV–vis absorption spectroscopy, fluorescence, and X-ray crystallography. The compound binds DNA and interacts in various ways with the model protein lysozyme. Remarkably, structural data revealed that the complex can bind lysozyme via non-covalent interactions, retaining its five-coordinate geometry.

This communication describes extremely efficient homogeneous iron(III) catalysts for the synthesis of solketal from glycerol and acetone. The activities are the highest ever reported so far for this type of reaction, with TOFs up to 10 5 h − 1 at negligible catalyst loading.

Stable five-coordinate Pt(II) complexes have been highlighted as a promising and original platform for the development of new cytotoxic drugs. Their interaction with proteins has been scarcely studied. Here, the reactivity of the five-coordinate Pt(II) compound [Pt(I)(Me) (dmphen)(olefin)] (Me = methyl, dmphen = 2,9-dimethyl-1,10-phenanthroline, olefin = dimethylfumarate) with the model proteins hen egg white lysozyme (HEWL) and bovine pancreatic ribonuclease (RNase A) has been investigated by X-ray crystallography and electrospray ionization mass spectrometry. The X-ray structures of the adducts of RNase A and HEWL with [Pt(I)(Me)(dmphen)(olefin)] are not of very high quality, but overall data indicate that, upon reaction with RNase A, the compound coordinates the side chain of His105 upon releasing the iodide ligand, but retains the pentacoordination. On the contrary, upon reaction with HEWL, the trigonal bi-pyramidal Pt geometry is lost, the iodide and the olefin ligands are released, and the metal center coordinates the side chain of His15 probably adopting a nearly square-planar geometry. This work underlines the importance of the combined use of crystallographic and mass spectrometry techniques to characterize, in detail, the protein&ndash, metallodrug recognition process. Our findings also suggest that five-coordinate Pt(II) complexes can act either retaining their uncommon structure or functioning as prodrugs, i.e., releasing square-planar platinum complexes as bioactive species.

The synthesis and characterization of N,N′-diethyl (L-Et,Et) and N-ethyl,N′-methyl (L-Et,Me) glyoxal-bridged cyclam ligands are described, together with the X-ray crystal structure of the complex [MnCl2(L-Et,Me)]. Bleaching of morine in the presence of hydrogen peroxide by the corresponding Mn catalysts [MnCl2(L-Et,Et)], [MnCl2(L-Et,Me)] and [MnCl2(L-Me,Me)] has been studied in aqueous solution at three different pH values (8.0, 8.75, and 9.0). The results clearly show that increasing pH has a different effect on the three catalysts, and that the dimethyl derivative is by far the most active.

It is described the simple design of a series of N,N′,O,O′-chiral ligands (elpaN-salen-H2), which represent a subset of the elpaN-type library of ligands based on β-1,2- d -glucodiamine. The corresponding Mn(III) complexes were examined in the asymmetric epoxidation of styrenes with satisfactory results, e.g. cis-β-methylstyrene was functionalised in ees up to 88%.

A homogeneous supported catalyst based on Zn(II) was prepared by anchoring complex [Zn(OAc) 2 (N,N′-chelate)] on silica, where N,N′-chelate is a suitably functionalised di-imine ligand. The complex was able to promote the esterification and transesterification of acidic vegetable oils at 160 °C within two hours. The catalyst could be also easily recovered and immediately re-cycled.

This study aimed to optimize the zinc-catalyzed trans-esterification, and pointed to assess the effect of the solvent, the catalyst, its loading and the nature of the substrate. The screening disclosed the remarkable ability of zinc(II) acetate to promote the reaction in refluxing toluene at low catalyst loading. A significant improvement ensued with respect to recently results on the same reactions, in terms of less restrictive conditions and more convenient catalyst precursors.

New zinc(II) compounds containing functionalized Schiff bases have been prepared and characterized. The complexes catalyze the transesterification of soybean oil in mild conditions, and their activity can be modulated by a fine selection of the anions and/or of the substituents on the ancillary bidentate ligand. The compounds are active in the esterification of fatty acids and could therefore also be used to produce biodiesel from waste oils.

The coordinated olefin in dicationic platinum(II) and palladium(II) complexes [M(PNP)(olefin)](SbF6)2 (M = Pt, Pd; PNP = 2,6-bis(diphenylphosphinomethyl)pyridine; olefin = ethene, propene) is electrophilic enough to react with benzene rings activated by methoxy substituents. If the proton released by the aromatic ring is trapped by a base, stable σ-alkyl derivatives of the type [M(PNP)CH2CH(R)Ar](SbF6) or [M(PNP)CH(R)CH2Ar](SbF6) (R = H, Me) are formed; otherwise the M−C σ-bond can be cleaved by the proton, setting up a catalytic cycle that leads to the alkylated aromatic compound. The molecular structure of the σ-alkyl derivative [(PNP)PtCH2CH2−C6H2(OMe)3](BF4) has been determined by X-ray diffraction analysis, and the factors affecting the mechanism and the rates of the catalytic reaction have been qualitatively investigated and rationalized, showing that the rates of C−C bond formation and M−C bond cleavage are inversely correlated.

This work describes two sustainable methods for production and purification of azelaic acid (AA) to replace the current process of ozonolysis of oleic acid (OA). The first proceeds in two steps, coupling smooth oxidation of OA to 9,10-dihydroxystearic acid (DSA) with subsequent oxidative cleavage by sodium hypochlorite. An alternative methodology is also proposed, using a chemocatalytic system consisting of H2O2/H2WO4 for direct oxidative cleavage of the double bond of OA at 373 K. A convenient technique for separation and purification of azelaic acid is also proposed.

The ability of chiral diamine silver complexes to bind chiral and prochiral alkenes has been analyzed in detail. The stereoselectivity in binding of alkenes to a chiral ethanediamine silver complex has been investigated by NMR. The low-energy conformations of several small model complexes have been explored by DFT methods. By successive substitution of the computational model complexes, it has been possible to elucidate the role of each amine substituent in achieving successful discrimination of alkenes. The conformational space has been fully explored using small model systems, allowing an unbiased calculation of stereoselectivities that match well the experimental results. For a chiral allylic alcohol substrate, the correct stereoselectivity was obtained only when the structures were optimized with a continuum representation of the solvent. The discrepancy between gas phase and solution data is found to result from a competition between internal stabilization and solvation of the OH group of the substrate.

New chiral P,N-chelates o-Ph2PC6H4CHNR (R=carbohydrate residue) derived from d -glucose and d -mannose were described. The synthesis of palladium(0) and rhodium(I) complexes of respective formula [Pd(P,N-chelate)(fumarodinitrile)] and [Rh(1,5-cyclooctadiene)(P,N-chelate)]BF4 was performed. It was found that the ligands effectively discriminate between the enantioface of fumarodinitrile in the Pd(0) species, prompting up to 100% diastereomeric excess when R is a 2,3,4-tri-O-acetylated glucoside moiety linked to N through C6. The catalytic activity of the complexes towards allylic alkylation and olefin hydroboration was also examined.

Two classes of hydrophilic Pd0 complexes containing P,N and N,N sugar-based ligands were prepared and tested in the Suzuki–Miyaura cross-coupling reaction under environmentally friendly aqueous conditions. The best catalyst was tolerant towards different substrates, and its activity is comparable with the highest values reported so far for reactions in aqueous media [loading 0.0010 %, turnover frequency (TOF) 3.5 × 104 h–1].

New chiral diimino and diamino ligands derived from α- d -mannose and α- d -glucose are described. The ligands are obtained by introducing the appropriate nitrogen functions at C(2) and C(3) of the sugar rings. The ability of the new chelates to promote the asymmetric copper(I)-catalysed cyclopropanation of styrene has been investigated. The nature of both the sugars and the chelates is crucial in determining the enantioselectivity of the reaction.

The dicationic palladium(II) and platinum(II) complexes [(PNP)M(C2H4)](BF4)2 (1a, M = Pt; 1b, M = Pd; PNP = 2,6-bis((diphenylphosphino)methyl)pyridine) and [(PPP)Pt(C2H4)](BF4)2 (7; PPP = triphos) catalyze a cross-coupling reaction of ethylene with tri- and tetrasubstituted olefins, which can lead to both hydrovinylation and cyclopropanation products. The product ratio is strongly affected by the choice of the ligand and of the metal, the two limiting cases being 1a and 7, which selectively give the hydrovinylation and the cyclopropanation products, respectively.

The fragment [(chiral diamine)Ag]+ is a very useful reagent, both for the resolution of racemic alkenes and for the 1H or 13C NMR determination of the enantiomeric abundances of chiral olefinic compounds.

The coordinated olefin in dicationic platinum(II) and palladium(II) complexes [M(PNP)(olefin)](SbF6)2 (M = Pt, Pd; PNP = 2,6-bis(diphenylphosphinomethyl)pyridine; olefin = ethylene, propylene) reacts with β-dicarbonyl compounds (pentane-2,4-dione and methyl-3-oxobutanoate). If the proton released after the nucleophilic attack is trapped by a base, stable σ-alkyl derivatives [(PNP)M-CH2-CH(R)CH(Ac)COR′]SbF6 (R = H, Me; R′ = Me, OMe) are formed; otherwise the M−C σ-bond can be cleaved by the proton, in the rate-determining step of a catalytic cycle that leads to the alkylated dicarbonyl compound. The β-diketone is intrinsically more reactive than the β-ketoester, but in the catalytic reaction of the former an inhibition effect is observed in the case of the platinum catalyst.

The reactivity of cis-[PtII(Ar)(2-butyne)] fragments (Ar = Ph, 4-MeOC6H4, 4-CF3C6H4) in cationic complexes is described. Coordination of the unsatd. ligand is obsd. at low temp. Upon increasing at 298 K, a cascade of reactions affords a selective formation of indenes, e.g. 1-ethyl-1,2,3-trimethyl-1H-indene. Mechanistic implications of this domino-reaction are discussed.

The coordinated ethylene molecule in the dicationic complex [(PNP)Pt(CH2=CH2)](BF4)2 (PNP = 2,6-bis(diphenylphosphinomethyl)pyridine) undergoes nucleophilic attack by free internal alkenes, giving the isolable complexes [(PNP)Pt(CH2=CHCH(Me)CMeRR'](BF4)2 (R, R' = H, Me) and providing a new effective pathway for a chemo- and regio-selective catalytic hydrovinylation reaction.

Cationic nitrile platinum(II) complexes of formula [PtMe(RCN)(bipy)]+ undergo nucleophilic addition of carbanions −CH(COX)(COY) (X, Y= Me, OMe), −CH(CO2Me)CN and −CH(CN)2 to afford neutral products. According to the nature of the nucleophile, the organic ligand fragment displays either an imino enol or an enamine isomeric structure. The Pt−N bond can be cleaved upon reaction with acids with formation of the corresponding β-enaminodione.

By using the Corey diamine 1,2-diphenyl-N,N′-bis[(2,4,6-trimethylphenyl)methyl]-1,2-diaminoethane, Copper(I) olefin complexes are prepared. When the olefin is a racemic allylic alcohol, selective coordination of one enantiomer is observed. Cleavage with aqueous HCl or NaCN allows a two-steps resolution affording excellent enantiomeric excess.

Using saturation-transfer experiments and measurements of coalescence temperatures, the effects of phenanthroline ligands on the activation parameters for syn-anti isomerization, syn-anti proton exchange, and apparent rotation in six (eta3-allyl)palladium complexes have been studied. The rates of the processes are increased by the addition of ionic, coordinating ligands such as chloride indicating a pentacoordinated intermediate. By X-ray crystallography the structure of a potential intermediate of this type has been determined. Finally, using 2-(8-methoxy-1-naphthyl)-1,10-phenanthroline, it has been possible both to observe chiral induction on a deuterium-substituted eta3-allyl group and to find additional information on the mechanism of apparent rotation.

Alkenes, alkynes, 1,2- and 1,3-dienes react with [MR(N-N)(MeCN)] + (M = Pt or Pd; R = hydrocarbyl group; NN = bidentate nitrogen ligand) to give R-substituted derivatives. The organic fragment is generally retained within the metal environment in η 1 or η 3 coordination, except in the reaction of alkenes with Pd (II) complexes. In this case, a free R-substituted alkene is produced via a relatively fast β-elimination process from a Pd-alkyl intermediate. Different regiochemistries are detected in the reaction between monosubstituted olefins (propene or styrene) and homologous Pt and Pd complexes. The Pt-C bond is always formed with the terminal unsubstituted alkene carbon, while a preference toward the internal carbon, particularly if phenyl-substituted, is observed with Pd species. Neutral [MClR(N-N)] are markedly less reactive. In this case, when M = Pt, the unsaturated organic substrate generally adds to the metal affording fairly stable tbp five-coordinate complexes.

Coordinatively saturated carbene complexes of platinum(II) have been obtained by oxidative addition of [ClCHNMe2]Cl to Pt(0) precursors. The cationic products of general formula [PtCl(CHNMe2)(N,N-chelate)(olefin)]Cl have been characterized through NMR spectroscopy and for [PtCl(CHNMe2)(2,9-Me2-1,10-phen)(Z-MeO2CCHCHCO2Me)]Cl by X-ray diffractometry. The latter species reacts with nucleophiles affording dimethylformamide and the corresponding Pt(0) precursor [Pt(2,9-Me2-1,10-phen)(Z-MeO2CCHCHCO2Me)]. Attempts to obtain related complexes containing carbene groups PtCHY without a heteroatom in α-position (Y = CO2Et, CO2NMe2, CN) have led to the isolation of complexes of formula [PtR(dmphen){η1,η2-CH(Y)O2CCHCHCO2Me}] (R = Me, Ph), formally derived from an intramolecular nucleophilic addition to a carbene intermediate. The X-ray structure of a representative product, [PtMe(dmphen){η1,η2-CH(CO2Et)O2CCHCHCO2Me}], is reported.

Three cationic five-coordinate platinum(II) complexes bearing alkylmercury fragments as “ligands” have been isolated. The complexes of general formula [Pt(HgR)H2O(dmphen)(Z-R′O2CCH = CHCO2R′] (BF4) ( dmphen = 2,9- dimethyl -1,10- phenanthroline ; R, R ′ = Me ; = R = Me, R ′ = t Bu, R ′ = Me ) are stabilized by the factors operating in related neutral species. Two of the new complexes slowly demercuriate in solution, affording the mononuclear complexes [ Pt(Me)(H 2 O)(dmphen)(Z- R ′ O 2 CCH = CHCO 2 R ′)]( BF 4 ) ( R ′ = Me or t Bu . When R = t Bu , a slow redistribution is observed, yielding the trinuclear cluster [{Pt(dmphen)(Z-MeO2CCH = CHCO2Me(H2O)}2Hg](BF4)2. The structure of this complex has been determined by X-ray analysis.

Trigonal bipyramidal olefin-platinum complexes of the title chiral diamine (mestien) have been synthetized and their stereochemistry has been investigated by H-1 and C-13 NMR spectroscopy. The molecular structure of the complex PtClMe ((E)-ClCH = CHCl) (mestien) has been determined by X-ray diffraction analysis. The coordinated nitrogen atoms display a single configuration, and a high enantioface selectivity is observed in the coordination of prochiral olefins having a moderate lateral bulk. The selectivity can be correlated to the conformation adopted by the diamine ligand, which shows a remarkable similarity to those calculated for a proposed intermediate in the enantioselective dihydroxylation of olefins by osmium tetraoxide.