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Immobilization of redox active complexes as electrodes modifier is appealing for a large set of applications such as sensing, electrolysers or fuel cell. In this work iron based N-heterocyclic carbene complexes bearing an 3,4‑Ethylene dioxythiophene (EDOT) moiety in the side chain have been prepared following two different synthetic approaches determined by the length of the lateral chain. The approaches exploit carbonyldiimidazole (CDI) as the coupling agent between the –CH2OH moiety of the hydroxymethyl-EDOT and the –OH functionalized N-heterocyclic carbene iron complex or the imidazolium salt precursor. In both cases, the syntheses allow to obtain functional monomers suitable for electrochemical polymerization in the form of thin films on conducting substrates. The modified electrodes have been characterized by ATR-IR, showing successful copolymerisation to functionalized poly(3,4‑ethylene dioxythiophene) (PEDOT), by cyclic voltammetry (CV), demonstrating the dominant and reversible redox response of NHC-iron complexes, and by SEM-EDS, which provides the average copolymerisation ratio. The capability of the NHC-iron complex to act as a redox mediator has been assessed by using the functionalized device for glucose detection.

The catalytic activity of anionic ruthenium complexes toward the transformation of bio-ethanol to 1-butanol and higher alcohols is found to be dependent on the imidazolium counterion. After the identification of a parallel reaction involving the catalyst in hydrogen evolution, conversion and selectivity are impressively boosted by the addition of p-benzoquinones as co-catalysts. The catalytic system avoids the side reaction and led to highly competitive conversions up to 88% (0.2% mol ruthenium catalyst loading, 1.5% mol benzoquinone loading). Butanol and higher alcohols are produced in yields up to 85% (overall selectivity 97%) as a mixture of valuable alcohols for advanced biofuel and lubricants applications. The catalytic system can be recycled and the reaction shows comparable efficiency on a real matrix (alcohol from wine production chain wastes) even in the presence of significant amounts of water, thus closing a hypothetic economic circle. A reaction mechanism is proposed for the most promising ruthenium complex working in cooperation with the most efficient co-catalyst: p-benzoquinone.

The chemistry of [Fe2Cp2(CO)4] (1-Fe; Cp = η5-C5H5) has been widely investigated, and straightforward carbonyl/isocyanide substitution, followed by isocyanide alkylation, provides access to a variety of aminocarbyne complexes, displaying a rich and versatile reactivity. On the other hand, the parallel chemistry of [Ru2Cp2(CO)4] (1-Ru) has been much less developed, and relevant structural/bonding aspects scarcely elucidated. We report an IR study on 1-Ru in different solvents and in the solid state. The IR data of [M2Cp2(CO)3(CNR)] (M = Ru, R = 2,6-C6H3Me2 = Xyl, 2a-Ru; M = Ru, R = CH2Ph = Bn, 2b-Ru; M = Ru, R = Me, 2c-Ru; M = Fe, R = Xyl, 2a-Fe; M = Fe, R = Bn, 2b-Fe; M = Fe, R = Me, 2c-Fe) and [M2Cp2(CO)3{μ-CNR(Me)}]CF3SO3 (M = Ru, R = Xyl, 4a-Ru; M = Ru, R = Bn, 4b-Ru; M = Ru, R = Me, 4c-Ru; M = Fe, R = Xyl, 4a-Fe; M = Fe, R = Bn, 4b-Fe; M = Fe, R = Me, 4c-Fe) are comparatively presented, and the back-donation from the dimetallic core to π-acceptor ligands in complexes 4 is discussed. A new synthetic procedure to access 2a-Ru is reported, affording [Ru2Cp2(CO)2(CNXyl)2] (3) as by-product, as well as the single crystal X-ray structures of 2b-Ru and 4b-Ru. DFT calculations were carried out to elucidate the relative stability of isomeric forms within the series of isocyanide adducts 2-Ru and 3

A process for obtaining higher aliphatic alcohols starting from aliphatic primary alcohols by condensation reactions is disclosed. Specifically, the process comprises a step in which an aliphatic primary alcohol is contacted in a 5 homogeneous phase with a catalyst mixture comprising a transition metal, a base and an additive; specifically, this additive can be selected from the classes of compounds of the isoquinolines N-oxide, quinolines N-oxide, pyridines N-oxide, benzoquinones, naphthoquinones, or TEMPO. In particular, the process can be carried out by contacting said aliphatic primary alcohol with a catalyst of a 10 recycled transition metal, with a freshly added base and with a recycled additive of the aforementioned type.

The reaction of [NEt4]2[Ni6(CO)12] in thf with 0.5 equiv of PCl3 affords the monophosphide [Ni11P(CO)18]3- that in turn further reacts with PCl3 resulting in the tetra-phosphide carbonyl cluster [HNi31P4(CO)39]5-. Alternatively, the latter can be obtained from the reaction of [NEt4]2[Ni6(CO)12] in thf with 0.8-0.9 equiv of PCl3. The [HNi31P4(CO)39]5- penta-anion is reversibly protonated by strong acids leading to the [H2Ni31P4(CO)39]4- tetra-anion, whereas deprotonation affords the [Ni31P4(CO)39]6- hexa-anion. The latter is reduced with Na/naphthalene yielding the [Ni31P4(CO)39]7- hepta-anion. In order to shed light on the polyhydride nature and redox behavior of these clusters, electrochemical and spectroelectrochemical studies were carried out on [Ni11P(CO)18]3-, [HNi31P4(CO)39]5-, and [H2Ni31P4(CO)39]4-. The reversible formation of the stable [Ni11P(CO)18]4- tetra-anion is demonstrated through the spectroelectrochemical investigation of [Ni11P(CO)18]3-. The redox changes of [HNi31P4(CO)39]5- show features of chemical reversibility and the vibrational spectra in the νCO region of the nine redox states of the cluster [HNi31P4(CO)39]n- (n = 3-11) are reported. The spectroelectrochemical investigation of [H2Ni31P4(CO)39]4- revealed the presence of three chemically reversible reduction processes, and the IR spectra of [H2Ni31P4(CO)39]n- (n = 4-7) have been recorded. The different spectroelectrochemical behavior of [HNi31P4(CO)39]5- and [H2Ni31P4(CO)39]4- support their formulations as polyhydrides. Unfortunately, all the attempts to directly confirm their poly hydrido nature by 1H NMR spectroscopy failed, as previously found for related large metal carbonyl clusters. Thus, the presence and number of hydride ligands have been based on the observed protonation/deprotonation reactions and the spectroelectrochemical experiments. The molecular structures of the new clusters have been determined by single-crystal X-ray analysis. These represent the first examples of structurally characterized molecular nickel carbonyl nanoclusters containing interstitial phosphide atoms.

A series of diiron complexes based on the [Fe2Cp2(CO)x] skeleton (Cp = η5-C5H5, x = 2, 3; η4-C5H5Ph in place of one Cp in one case) and containing different bridging hydrocarbyl ligands (aminocarbyne, thiocarbyne, allenyl) were preliminarily investigated for their anticancer potential. The water solubility, stability in water and in the presence of a cell culture medium, and octanol/water partition coefficient were evaluated by spectroscopic techniques. The cytotoxicity was assessed in vitro toward the human ovarian carcinoma cell line A2780, the human triple negative breast cancer cell line MDA-MB-231, and the human vascular smooth muscle cell line SMC. Some aminocarbyne complexes exhibited a potent cytotoxicity, with IC50 values in the low micromolar/nanomolar range, and a strong selectivity for the A2780 cells in comparison to the SMC cell line. Several experiments were carried out in order to give insight into the mode of action of selected compounds, including an assessment of catalytic NADH oxidation and ROS production and studies of binding with DNA and with a model protein.

The reactivity of the dinuclear complex dicarbonyl[η4-3,4-bis(4-methoxyphenyl)-2,5-diphenylcyclopenta-2,4-dienone] (2) with imidazolium salts has been studied using a library of variously functionalized imidazolium salts, and leading to a class of ruthenium anionic complexes of the type [dicarbonylη4-3,4-bis(4-methoxyphenyl)-2,5-diphenylcyclopenta-2,4-dienone (halide)Ru][1,3-disubsittuted-imidazolium] (4) in the form of ion pair with imidazolium. The reaction is clean, general and quantitative and the complexes formed are stable to air and moisture both in the solid state and in solution. The ionic complexes 4 show affinity for ionic liquids and represent stable precursors of a catalytic active species, likely similar to those generated from Shvo catalyst, a well-established homogeneous bifunctional catalyst for hydrogen transfer. Our approach allows the use of green ionic liquids (IL) as solvents, providing better control of catalytic reactions involving 4, and easier catalyst recycle. IL-supported ionic pair catalysts exhibit interesting catalytic activity (up to > 99 % of conversion) in the transfer hydrogenation of a model compound such as 4-fluoroacetophenone. The IL-supported redox catalysts can be also recycled exploiting the biphasic nature of the system. The synthetic method here discussed represents a novelty within the field of IL-supportation and is potentially useful for the heterogenization of the catalysts.

The design of new flame retardants (FR) that avoid the use of halogen and phosphorus additives is challenging and urgent. Herein we report on the synthesis of bis-amino functionalized N-heterocyclic carbene cyclopentadienone iron complexes aimed at promoting the production of iron containing epoxy resins. Iron complexes are successfully employed to obtain high Tg thermosets with as low as 5% hardener content. Moreover the obtained resins display an impressive charring ability that paves the way to the application of such systems for material with improved flame behavior.

Viene descritto un procedimento per l’ottenimento di alcoli alifatici superiori a partire da alcoli primari alifatici tramite reazioni di condensazione. Nello specifico il procedimento comprende un passaggio in cui si mette a contatto in fase omogenea un alcol primario alifatico con un catalizzatore contenente un metallo di transizione, una base ed un additivo; nello specifico tale additivo può essere scelto fra le classi di composti delle isochinoline N-ossido, chinoline N-ossido, piridine N-ossido, benzochinoni, naftochinoni o TEMPO. In particolare, il procedimento può essere effettuato mettendo a contatto detto alcol primario alifatico con un catalizzatore di un metallo di transizione di riciclo, con una base aggiunta di fresco e con un additivo di riciclo del tipo suddetto.

The front cover picture supplied by Carla Carfagna and co‐workers depicts an efficient process for the diastereospecific bis‐alkoxycarbonylation of 1,2‐disubstituted olefins, leading to the synthesis of 2,3‐disubstituted‐succinic diesters. Using Pd(TFA)2 as palladium source, bis‐(2,6‐dimethylphenyl)‐2,3‐dimethyl‐1,4‐diazabutadiene as ligand and p‐benzoquinone as oxidant, aliphatic, aromatic, cyclic olefins and unsaturated fatty acid methyl esters, have been successfully converted in the presence of different alcohols, under mild reaction conditions (PCO =4 bar, T = 20 °C). Further details can be found in the full paper on pages 3507–3517 (D. Olivieri, F. Fini, R. Mazzoni, S. Zacchini, N. Della Ca′, G. Spadoni, B. Gabriele, R. Mancuso, V. Zanotti, C. Carfagna, Adv. Synth. Catal. 2018, 360, 3507–3517: DOI 10.1002/adsc.201701597).

The diiron μ-aminocarbyne complexes [Fe2{μ-CN(Me)(R)}(μ- CO)(CO)(CNR′)(Cp)2][SO3CF3] (R = R′ = Xyl, 2a; R = Xyl, R′ = Me, 2b; R = Xyl, R′ = But, 2c; R = Xyl, R′ = p-C6H4CF3, 2d; R = Me, R′ = Xyl, 2e; Xyl = 2,6-Me2C6H3), containing an isocyanide ligand, have been obtained via CO replacement with the appropriate CNR′ ligand from [Fe2{μ-CN(Me)(R)}(μ- CO)(CO)2(Cp)2][SO3CF3] (R = Xyl, 1a; R = Me, 1b). Compound 2a, upon treatment with NaBH4 and heating at reflux temperature in THF solution, is transformed into the aminocarbene−aldimine [Fe2{μ-η1(C):η1(N)-CN(Me)(Xyl)CHN(Xyl)}(μ-CO)2(Cp)2] (3) in moderate yield. The reactions occurs via formation of the formimidoyl complex [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){C- (H)NXyl}(Cp)2] (4a), which has been isolated by reacting 2a with NaBH4 at 0 °C. Likewise, the formimidoyl complex [Fe2{μ-CN(Me)(R)}(μ-CO)(CO){C(H)NR′}(Cp)2] (R = Xyl, R′ = Me, 4b; R = Me, R′ = Xyl, 4c) have been obtained from 2b,e, respectively, upon reaction with NaBH4, but these complexes do not convert into the aminocarbene−aldimine complexes analogous to 3. Reactions of 2a with other nucleophiles have been investigated, without obtaining any product similar to 3. Complex 2a reacts with NaCN or with LiPPh2, resulting in isocyanide displacement and formation of [Fe2{μ-CN(Me)(Xyl)}(μ- CO)(CO)(CN)(Cp)2] (5) and [Fe2 {μ-CN(Me)(Xyl)}(μ-CO)(CO)(PPh2)(Cp)2] (6), respectively. Addition of the organocopper reagent Li2CuCNMe2 to 2a affords the acyl complex [Fe2{μ-CN(Me)(Xyl)}(μ-CO){C(O)Me}(CNXyl)(Cp)2] (7). The thiocarbyne complex [Fe2{μ-CSMe}(μ-CO)(CO)(CNXyl)(Cp)2][SO3CF3] (8), which shows analogies with 2a, reacts with NaBH4, affording the carbene derivative [Fe2 μ-{C(SMe)(H)}(μ-CO)(CO)(CNXyl)(Cp)2] (9). The molecular structures of 2a and 3 have been determined by X-ray diffraction studies.

A simple and expeditious microwave-assisted procedure for the synthesis of a variety of Shvo-type ruthenium complexes has been developed by reacting Ru3(CO)12 with variously functionalized tetraarylcyclopentadienones under microwave irradiation in MeOH. Ligand precursors have also been prepared under microwave heating by a bis-aldol condensation of 1,3-diphenylacetone with variously functionalized aromatic diketones. All the reactions were very fast and clean, leading to good yields and purities.

The diiron µ-aminocarbyne imidoyl complexes [Fe2µ-CN(Me)(R)(µ-CO)(CO)C(C≡CR′)=NXylCp2] [R = Xyl, R′ = Ph (1a);[1] R = Xyl, R′ = Tol (1b);[1] R = Me, R′ = Ph (1c); R = Me, R′ = SiMe3(1d); Xyl = 2,6-C6H3Me2, Tol = 4-C6H4Me] have been prepared by the addition of lithium acetylides to precursors containing a terminal isocyanide ligand. The treatment of 1a–c with CF3SO3CH3afforded the alkynyl(amino)carbene derivatives [Fe2µ-CN(Me)(R)(µ-CO)(CO)C(C≡CR′)N(Me)(Xyl)Cp2][SO3CF3] [R = Me, R′ = Ph (2a); R = Xyl, R′ = Ph (2b); R = Xyl, R′ = Tol (2c)] in high yields. The reactions of 2b,c with CH3OH/NaBF4, NH2R and NaBH4led to [Fe2µ-CN(Me)(Xyl)(µ-CO)(CO)C(CH=C(Ph)OMe)N(Me)(Xyl)Cp2][BF4] (3), [Fe2µ-CN(Me)(Xyl)(µ-CO)(CO)C(CH=C(Tol)NHR)N(Me)(Xyl)Cp2][SO3CF3] [R = Et (4a); R = Ph (4b)], and [Fe2µ-CN(Me)(Xyl)(µ-CO)(CO)C(CH=CHTol)N(Me)(Xyl)Cp2][SO3CF3] (5) in yields of 65–80 %. Complexes 3–5 were formed by the selective functionalization of the alkynyl group in 2b,c. Complex 2c reacted with NaCH(CN)2/CH2(CN)2and NaCH(CO2Me)2to yield [Fe2µ-CN(Me)(Xyl)(µ-CO)(CO)CN(Me)(Xyl)CH=C(Tol)C(CN)C(NH2)C(CN)2Cp2] (6) and [Fe2µ-C(NXyl)C(C(Tol)=C(CO2Me)2)CN(Me)(Xyl)(µ-CO)2Cp2] (7) in yields of 65 and 60 %, respectively. All the products were purified by alumina chromatography, alumina being presumably involved in the formation of 3, and characterized by elemental analysis and IR and NMR spectroscopy. The structures of 2b, 3, 5, and 6 were ascertained by single-crystal X-ray diffraction analysis.

A large number of catalysts for hydrogen evolution reaction (HER) that are related (structurally and/or functionally) to the active site of [FeFe]-hydrogenases (H-cluster) has been proposed in the past few decades. Very recently, a novel recipe for HER catalysts has been added to the list. This consists in the combination of a diiron core, a ligand that can act as an intramolecular weak base to support protonation (both features that are common to the H-cluster), and a peculiar carbyne ligand that bridges the two metal centers. For instance, complex [Fe2{μ-CNMe2}(μ-CO)(CO)(CN)Cp2] (4) proved to be catalytically active towards HER. The novelty related to this family of biomimicry is not only structural, but also mechanistic. Indeed, an unprecedented (in the context of hydrogenase mimicry) ligand-based mechanism of HER, which avoids protonation at metal, has been dissected by DFT. In order to increase catalytic activity of this “non dithiolate based” system, a systematic search of ligand modification is therefore desirable. In this regard, herein we present results of replacing CN− (the proton shuttle in 4) by other ligands such as CNCH2Ph (5), PPh3 (6) or azide (7). The redox behavior of these compounds has been tested, in the absence and presence of a proton source. CV experiments combined with DFT calculations have revealed and rationalized critical points entailed by modifications of stereo-electronic features of 4. However, understanding the key factors underlying the absence of catalytic activity of these new compounds can be beneficial for the design of future improved biomimicry related to HER. As an example, properly tailored hydrocarbyl complexes replacing dithiolates at the Fe2 core might allow recovering the fruitful electronic properties of cyanides, when coordinated to metal centers.

Homologation of bioethanol to butanol and higher alcohols by means of Guerbet reaction was performed with a novel ruthenium based bifunctional catalyst under homogeneous conditions in the presence of a basic cocatalyst. Reaction screening demonstrated that the new catalyst shows conversions and selectivity comparable with some of ruthenium based bifunctional catalysts recently reported in the literature. The reaction occurs in pure ethanol as well as in ethanol from wine waste furnished by CAVIRO distillery with up to 46% conversion of ethanol and an overall selectivity to higher alcohols of 91% and a minor carbon loss. Based on the laboratory results, an industrialization study was carried out in order to propose a viable technological solution. The experimental data consistency was verified, and the results were up-scaled to design a reactor working in a batch or, potentially, semibatch operation mode. Further analysis of the overall process, together with the introduction of dedicated figures of merit have allowed the estimation of the process performance both in mass and energetic terms, and the outcome was integrated into a life cycle analysis. Although preliminary, the multidisciplinary approach has converged toward complementary results; more specifically, the adoption of the base cocatalyst NaOEt has showed similar performance in terms of specific alcohols production and energy demand compared to the NaOH case. Moreover, this last case proves to be better from an environmental perspective (LCA).

The synthesis of a bis-amino-functionalized iron cyclopentadienone N-heterocyclic carbene complex (1) has been fine tuned to develop an hardener for the production of a novel hybrid epoxy resin (EP) with the aim of also reducing fire hazard. The synthesized organometallic complex well performs as curing agent both with DGEBA, preliminary employed, and the commercial pre-polymer Elan-tron® EC 157 in different formulations (loading range 5, 7.5, 10%wt). Thermogravimetric analyses revealed that curing temperature shows a significant intumescent char residual (yield 25%), possibly to due iron presence. DSC indicated that reaction rate and glass transition increase with complex 1 content, and under isothermal conditions the best performances have been identified at 170 °C and 7.5%wt of 1. The latter conditions has been finally employed for tests in cone calorimeter displaying a charring action of the complex included in the resins, together with an early ignition that has to be addressed playing on the formulation and chemical structure of the hardener.

The one-electron reduction of a diiron cationic complex revealed unique features: cleavage of the diiron structure occurred despite a multidentate bridging C

A new synthetic route for obtaining α-6-hydroxy-6-methyl-4-enyl-2H-pyran-3-one, a useful synthon for the preparation of biologically active compounds, has been developed from the bio-based platform derivative (2,5-bis-hydroxymethylfuran) BHMF. The reaction occurs with good selectivity in water, under mild conditions and employing an heterogeneous recyclable acid (Amberlyst 15®) as catalyst, avoiding the use of oxidizing agents. The reaction provides access to poly-oxygenated compounds characterized by a molecular motif commonly found in many natural products.

The bis-tetrazolate dianion [1,2 BTB](2-), which is the deprotonated form of 1,2 bis-(1H-tetrazol-5-yl)benzene [1,2-H2BTB], is for the first time exploited as an ancillary N^N ligand for negatively charged [Ir(C^N)2(N^N)](-)-type complexes, where C^N is represented by cyclometalated 2-phenylpyridine (ppy) or 2-(2,4-difluorophenyl)pyridine (F2ppy). The new Ir(iii) complexes [Ir(ppy)2(1,2 BTB)]- and [Ir(F2ppy)2(1,2 BTB)]- have been fully characterised and the analysis of the X-ray structure of [Ir(ppy)2(1,2 BTB)]- confirmed the coordination of the [1,2 BTB](2-) dianion in a bis chelated fashion through the N-atoms adjacent to each of the tetrazolic carbons. Both of the new anionic Ir(iii) complexes displayed phosphorescence in the visible region, with intense sky-blue (λmax = 460-490 nm) or aqua (λmax = 490-520 nm) emissions originating from [Ir(F2ppy)2(1,2 BTB)]- and [Ir(ppy)2(1,2 BTB)]-, respectively. In comparison with our very recent examples of anionic Ir(iii)tetrazolate cyclometalates, the new Ir(iii) tris chelate complexes [Ir(F2ppy)2(1,2 BTB)]- and [Ir(ppy)2(1,2 BTB)]-, display an improved robustness, allowing the study of their reactivity toward the addition of electrophiles such as H(+) and CH3(+). In all cases, the electrophilic attacks occurred at the coordinated tetrazolate rings, involving the reversible - by a protonation deprotonation mechanism - or permanent - upon addition of a methyl moiety - switching of their global net charge from negative to positive and, in particular, the concomitant variation of their photoluminescence output. The combination of the anionic complexes [Ir(F2ppy)2(1,2 BTB)]- or [Ir(ppy)2(1,2 BTB)]- with a deep red emitting (λmax = 686 nm) cationic Ir(iii) tetrazole complex such as [IrTPYZ-Me]+, where TPYZ-Me is 2-(2-methyl-2H-tetrazol-5-yl)pyrazine, gave rise to two fully Ir(iii)-based soft salts capable of displaying additive and O2-sensitive emission colours, with an almost pure white light obtained by the appropriate choice of the ionic components.

The iron complex [Fp][OTf] {Fp(+) = [Fe(CO)(2)(Cp)](+), OTf- = SO3CF3-} is an efficient catalyst for the direct substitution of the OH group in ferrocenylmethanol [Fc-CH2OH] by thiols, aromatic amines, diphenylphosphane, and carbon nucleophiles (furan, pyrrole, and indole). This approach offers a convenient route to ferrocenes containing side chains with different functional groups. The advantages of the method are associated with the use of a catalyst based on iron, which is a nontoxic and readily available transition metal, and in the direct OH substitution, which produces water as the only byproduct.

Diiron complexes with bridging hydrocarbyl ligands and containing CO and Cp ligands (Cp = η5-C5H5) have been investigated as possible electrocatalysts for H2 production. In particular, studies included the vinyliminium complexes [Fe2{μ-η1:η3-C(R′)=CRCNMe2}(μ-CO)(CO)- (Cp)2][SO3CF3] (R′ = Tol (4-MeC6H4), R = H, 1a; R′ = CH2OH, R = H, 1b; R′ = CH2OH, R = SPh, 1c), the vinylalkylidene [Fe2{μ-η1:η3- C(Tol)CHCHNMe2}(μ-CO)(CO)(Cp)2] (2), the aminoalkylidyne [Fe2{μ-CN(Me)(R)}(μ-CO)(CO)(L)(Cp)2][SO3CF3] (R = Me, L = CO, 3a; R = Me, L = NCMe, 3b; R = Xyl (2,6-Me2C6H3), L = CO, 3c), [Fe2{μ- CN(Me)2}(μ-L′)(CO)(L)(Cp)2] (L′ = CO, L = CN, 4; L′ = H, L = CO, 5), the thiocarbyne complexes [Fe2(μ-CSEt)(μ-CO)(CO)2(Cp)2][BF4], (6) and [Fe2(μ-CSMe)(μ-CO)(CO)(CN)(Cp)2] (7), and the alkylidene complexes [Fe2{μ-C(CN)(SMe)}(μ-CO)(CO)2(Cp)2][SO3CF3] (8) and [Fe2{μ-C(CN)(PMe2Ph)}(μ-CO)(CO)2(Cp)2][SO3CF3] (9). Cyclic voltammograms (CV) of the above complexes in CH3CN have been recorded in the presence of increasing amounts of acetic acid to evidence electrocatalytic proton reduction. In spite of the fact that the above diiron complexes do not resemble the typical diiron dithiolate model systems, the aminocarbyne 4 and the thiocarbyne complex 7 exhibit significant electrocatalytic properties for proton reduction (e.g., for 4, the turnover number (TON) is 15.5).

The reaction of [NEt

Readily synthesized aryl α-diimine derivatives have been used as efficient ligands for the palladium-catalyzed oxidative bis-alkoxycarbonylation reaction of 1,2-disubstituted olefins. The most active catalyst A was formed insitu from bis-(2,6-dimethylphenyl)-2,3-dimethyl-1,4-diazabutadiene and Pd(TFA)2(TFA=trifluoroacetate). This catalytic system was able to selectively convert 1,2-disubstituted olefins into 2,3-disubstituted-succinic diesters with total diastereospecificity, in good yields (up to 97%) with 2mol% of catalyst loading, under mild reaction conditions (4bar of CO at 20°C in presence of p- toluenesulfonic acid as additive and p-benzoquinone as oxidant). The optimized reaction conditions could be successfully applied to 1,2-disubstituted aromatic, aliphatic, cyclic olefins and to unsaturated fatty acid methyl esters, employing methanol or benzyl alcohol as nucleophiles. The use of the bulky, less reactive isopropyl alcohol has allowed to better understand the mechanisms involved in the catalytic process. The geometry of the carbonylated products can be explained as a consequence of a concerted syn addition of the Pd-alkoxycarbonyl moiety to the olefin C=C bond. Catalyst A was isolated, characterized and analyzed by single crystal X-ray diffraction analysis.

The vinyliminium complexes [Fe2μ-η1:η3-C(CO2Me)C(H)CN(Me)(R)(μ-CO)(CO)(Cp)2][SO3CF3] [R = Me, 1a; R = 4-C6H4OMe, 1b; R = CH2Ph, 1c] react with primary amines (NH2R′ R′= Me, Et, Bun, (CH2)2NH2, CH2Ph) and ammonia to give the corresponding bridging amidine-alkylidene complexes [Fe2μ-κ1(N): η1(C): η1(C)-C(CO2Me)CH2CN(Me)(R)(NR′)(μ-CO)(CO)(Cp)2] (4a-j) in 70-90% yields. Likewise, the vinyliminium complex [Fe2μ- η1:η3-C(CO2Me)C(CO2Me)CN(Me)2(μ-CO)(CO)(Cp)2][SO3CF3] (1d) reacts with NH2R′ (R′= Me, Et) to form the corresponding amidine-alkylidene [Fe2μ-κ1(N): η1(C): η1(C)-C(CO2Me)CH(CO2Me)C(NMe2)(NR′)(μ-CO)(CO)(Cp)2] [R′= Me, 8a; R′ = Et, 8b], generating selectively one of the two diastereoisomers associated with the presence of the methylidene unit CH(COO2Me)- within the bridging ligand. Amination of the vinyliminium complexes 1a-c takes place also with hydrazine, resulting in the formation of [Fe2μ-κ1(N): η1(C): η1(C)-C(CO2Me)CH2CN(Me)(R)(NNH2)(μ-CO)(CO)(Cp)2] [R = Me, 5a; R = 4-C6H4OMe, 5b; R = CH2Ph, 5c]. Complexes 1b and 1d react with NHMe2, affording the en-(1,1)diamino-alkylidene complexes [Fe2μ- η1:η3-C(CO2Me)C(R′)C(NMe2)N(Me)(R)(μ-CO)(CO)(Cp)2] [R = 4-C6H4OMe, R′ = H, 9b; R = Me, R′ = CO2Me, 9d]. The reaction of 1c with piperidine results in formation of the amidine-alkylidene [Fe2μ-κ1(N): η1(C): η1(C)-C(CO2Me)CH2CN(Me)(CH2Ph)(CH2CH2CH2CH=CH2)(μ-CO)(CO)(Cp)2] (10), which implies piperidine ring-opening. All the products have been purified by alumina chromatography and characterized by analytical and spectroscopic methods; in addition, the molecular structures of 4f, 5b, and 8a have been ascertained by X-ray diffraction studies.

Diiron µ-aminocarbyne compounds, 1a–e, are prepared in two steps from Fe2Cp2(CO)4, negating the need for difficult purification procedures of intermediate species; they are efficiently isolated by alumina chromatography. Minor amounts of µ-aminocarbyne aryl isocyanide compounds, 2a–c, are obtained as side products. The structures of the cations in 1a,c,e are calculated using DFT; the carbyne carbon is generally predicted to be the thermodynamic site of hydride addition, in agreement with a previous experimental finding concerning 1a. Accordingly, the reaction of 1e with NaBH4 affords a bridging aminocarbene complex, 4, in 85 % yield. Otherwise, the reaction of 1c with NaBH4 yields the aminocarbyne–cyclopentadiene derivative 3 (70 %), presumably as a consequence of the steric protection exerted by the xylyl–methyl groups towards the carbyne moiety. The sequential treatment of 1a,c with Li2CuCNMe2 and MeSO3CF3 affords 5a,b, comprising both aminocarbyne and alkoxycarbene ligands. In accordance with DFT calculations, the alkoxycarbene moiety in 5a is the most favourable site for nucleophilic attack. Thus, the reactions of 5a with NH2R (R = Et, iPr) and NBu4CN, respectively, give the aminocarbyne/aminocarbene complexes, 6a,b, and the aminocarbyne-α-cyanoalkyl 7. All the products are fully characterized by spectroscopic and analytical methods; moreover, the structures of 1a, 1d, 6a and 7 are elucidated by single-crystal X-ray diffraction studies.

Insertion of propyne or 2-butyne into the Fe-carbyne bond belonging to the fragment [Fe2Cp2(CO)(μ-CO)μ-CNMe(R)]+ (R = Me or Xyl = 2,6-C6H3Me2) was investigated via density functional theory (DFT), and plausible intermediates were identified along the formation of the vinyliminium complexes [Fe2Cp2(CO)(μ-CO)μ-η1:η3-C(Me)C(R″)CN(Me)(R)]SO3CF3, [2a-d]+, thus allowing us to explain regio- and stereochemical features. The X-ray structure of [2a]SO3CF3 (R = Me, R″ = H) was determined by single crystal X-ray diffraction. Novel C-C and C-S bond forming pathways involving the vinyliminium ligand were then explored. Thus, [2b]SO3CF3 (R = Xyl, R″ = H) reacted with cyclopentadiene (or cyclopentene), triphenylphosphonium methylide, and benzyl bromide, in tetrahydrofuran in the presence of sodium hydride, respectively, to give [Fe2Cp2(CO)(μ-CO)μ-η1:η2-C(Me)CC(CH)4CN(Me)(Xyl)], 3, [Fe2Cp2(CO)(μ-CO)μ-η1:η2-C(Me)C(CH2)CN(Me)(Xyl)], 4, and [Fe2Cp2(CO)(μ-CO)μ-η1:η3-C(Me)C(CH2Ph)CN(Me)(Xyl)]Br, [5]Br, in good yields. Unstable complex 4 (detected by IR spectroscopy) readily converted into [2c]SO3CF3 (R = Xyl, R″ = Me) upon HSO3CF3 protonation of the methylide function. [5]Br was obtained as E/Z isomeric mixture, which was then quantitatively converted into the most stable Z form, by heating in methanol solution at 50 °C. The reactions of [2c,d]SO3CF3 (R = Me, Xyl, R″ = Me) with PhSSPh/NaH selectively yielded the aminoalkylidyne species [Fe2Cp2(SPh)(CO)(μ-CO)μ-CN(Me)(Xyl)], 6, and the bis-alkylidene [Fe2Cp2(CO)(μ-CO)μ-η1:η2-C(Me)C(Me)(SPh)CN(Me)2], 7, respectively, probably via the intermediacy of radical compounds 2c,d. The structures of 3-7 and 2c,d were elucidated by DFT calculations, and the isolated products were characterized by analytical and spectroscopic methods.

The one-electron reduction of a diiron cationic complex revealed unique features: cleavage of the diiron structure occurred despite a multidentate bridging C3 ligand and was accompanied by the clean dissociation of one ?5-cyclopentadienyl ring and one iron as isolated units. Thus, the iron(II)-iron(II) ?-vinyliminium complex [Fe2Cp2(CO)(?-CO){?-?1:?3-C3(Et)C2HC1N(Me)(Xyl)}][SO3CF3] ([1a]SO3CF3) reacted with cobaltocene in tetrahydrofuran (THF), affording the iron(II) vinylaminoalkylidene [FeCp(CO){C1N(Me)(Xyl)C2HC3(Et)C(?O)}] (2a) in 77% yield relative to the C3 ligand. Analogously, [FeCp(CO){C1N(Me)(Xyl)C2HC3(CH2OH)C(?O)}] (2b) was obtained in 64% yield from the appropriate diiron precursor and CoCp2. The formation of 2a is initiated by the one-electron reduction of [1a]+, followed by a reversible intramolecular rearrangement terminating with the irreversible release of CpH (NMR and gas chromatography-mass spectrometry) and Fe [electron paramagnetic resonance (EPR) and magnetometry]. The key intermediate iron(I) ferraferrocene (3) was detected by EPR and IR spectroelectrochemistry, while the related species 3-H-3 was isolated after the addition of a hydrogen source and then identified by X-ray diffraction. A plausible mechanism for the route from [1a]+ to 3 was ascertained by density functional theory calculations. The dication [1a]2+, displaying both carbonyl ligands in terminal positions, and the anion [3]- were electrochemically generated. The functionalized diiron compounds 4 (52% yield) and 5 (62%) were afforded through the activation of O2 and S8 by a radical intermediate along the reductive pathway of [1a]+. The reaction of [Fe2Cp2(CO)(?-CO){?-?1:?3-C(SiMe3)CHCN(Me)(Xyl)}][SO3CF3] ([1c]SO3CF3) with CoCp2 in THF afforded [Fe2Cp2(C?CSiMe3)(CO)(?-CO){?-CNMe(Xyl)}] (6) in 65% yield.

DFT has been used to investigate viable mechanisms of the hydrogen evolution reaction (HER) electrocatalyzed by [Fe

C-N bond formation involving carbon monoxide and isocyanide ligands is promoted by addition of a series of lithium acetylides to a diiron mu-aminocarbyne complex, i.e. [Fe2{mu-CN(Me)(Xyl)}(mu-CO)(CO)(CNXyl)(Cp)2][SO3CF3] (Xyl = 2,6-C6H3Me2). The reaction proceeds in three steps, i.e. (a) acetylide addition to the CO ligand, (b) acetylide migration to the isocyanide ligand, and (c) C-N coupling. The X-ray molecular structures of 1a and 1b comprise the first example of a kappa(C,C')-N-carbonyl-aminocarbene ligand.

A straightforward and efficient synthetic route to novel Ru N-heterocyclic carbene (NHC) complexes by transmetallation of non-bulky silver NHC to ruthenium dicarbonyl tetraarylcyclopentadienone is described. The same procedure with sterically demanding NHC leads to unprecedented heterobimetallic Ru–Ag(NHC) complexes.

Two neutral cyclometalated Ir(III)-tetrazolato complexes that differ by variations of the substituents on either the phenylpyridine or the tetrazolate ligand have been converted into the corresponding methylated and cationic analogues. NMR (1H and 13C) characterization of the Ir(III) complexes provided the results in agreement with the chemo- and regioselective character of methylation at the N-3 position of the Ir(III)-coordinated tetrazolato ring. This evidence was further corroborated by the analysis of the molecular structures of the cationic complexes obtained by X-ray diffraction. In view of the photophysical properties, the addition of a methyl moiety to neutral Ir(III) tetrazolates, which behave as sky-blue or orange phosphors, caused a systematic red shift of their phosphorescence output. The transformation of neutral Ir(III) tetrazolates into cationic Ir(III)-tetrazole complexes was screened for any eventual antimicrobial activity in vitro against Gram negative (E. coli) and Gram positive (D. radiodurans) microorganisms. While both kinds of complexes were not active against E. coli, the conversion of the neutral Ir(III) tetrazolates into the corresponding methylated and cationic Ir(III)tetrazole derivatives determined the turn-on of a good to excellent antimicrobial activity toward Gram positive Deinococcus radiodurans, a non-pathogenic bacterium that is listed as one of the toughest microorganisms in light of its outstanding resistance to radiation and oxidative stress.

DFT has been used to investigate viable mechanisms of the hydrogen evolution reaction (HER) electrocatalyzed by [Fe2(CN){μ-CN(Me)2}(μ-CO)(CO)(Cp)2] (1) in AcOH. Molecular details underlying the proposed ECEC electrochemical sequence have been studied, and the key functionalities of CN- and amino-carbyne ligands have been elucidated. After the first reduction, CN- works as a relay for the first proton from AcOH to the carbyne, with this ligand serving as the main electron acceptor for both reduction steps. After the second reduction, a second protonation occurs at CN- that forms a Fe(CNH) moiety: i.e., the acidic source for the H2 generation. The hydride (formally 2e/H+), necessary to the heterocoupling with H+ is thus provided by the μ-CN(Me)2 ligand and not by Fe centers, as occurs in typical L6Fe2S2 derivatives modeling the hydrogenase active site. It is remarkable, in this regard, that CN- plays a role more subtle than that previously expected (increasing electron density at Fe atoms). In addition, the role of AcOH in shuttling protons from CN- to CN(Me)2 is highlighted. The incompetence for the HER of the related species [Fe2{μ-CN(Me)2}(μ-CO)(CO)2(Cp)2]+ (2+) has been investigated and attributed to the loss of proton responsiveness caused by CN- replacement with CO. In the context of hydrogenase mimicry, an implication of this study is that the dithiolate strap, normally present in all synthetic models, can be removed from the Fe2 core without loss of HER, but the redox and acid-base processes underlying turnover switch from a metal-based to a ligand-based chemistry. The versatile nature of the carbyne, once incorporated in the Fe2 scaffold, could be exploited to develop more active and robust catalysts for the HER.

The bio-based substrate and target product 2,5-bishydroxymethylfuran (BHMF) demonstrated to influence the reaction kinetics in the homogeneous reduction of 5-hydroxymethylfurfural (HMF) catalyzed by the Ru-based Shvo's catalyst. A combined experimental and computational study supports an important role of the –CH2OH moiety which may be involved in the catalytic cycle toward the formation of different intermediates from HMF and BHMF. The reaction is selective and leads to quantitative formation of BHMF working under mild conditions. Furthermore, an optimized recycling procedure which avoids the use of water, allows recover and reuse of the catalyst without loss of activity. The mechanistic insights from this work may be extended to provide a general description of the chemistry of the Shvo's catalyst feeding further bio-based molecules.