Search

Poly(delta-valerolactone) (PVL) was synthesized by ring-opening polymerization (ROP), employing tin(II) acetate (SnAcet(2)), lead(II) acetate trihydrate (PbAcet(2)center dot 3H(2)O) and cadmium(II) acetate dihydrate (CdAcet(2)center dot 2H(2)O) complexes as initiators without any co-initiator. The highest molecular weight PVL (45 438 g mol(-1), 91% yield) was obtained with CdAcet(2)center dot 2H(2)O. Characterization of the synthesized products was performed by FTIR, H-1 NMR, C-13 NMR, gel permeation chromatography (GPC), matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/TOF MS), TGA and DSC. Electrostatic data (natural bond orbital and Hirshfeld) and lowest unoccupied molecular orbital (LUMO) of the initiators were obtained by using several density functional theory methods (B3LYP, omega B97X-D, PBEPBE, BPV86, HSEH1PBE, MPW1PW91, M06 and M062X). In addition, the initiation stage of the ROP mechanism of delta-valerolactone with these metal acetate complexes was investigated at the omega B97X-D level with a mixed basis set. It was computationally determined that the most effective initiator was also CdAcet(2). The molecular weight variation of PVLs synthesized with these initiators can be associated with the combined evaluation of atomic charge, LUMO and orbital overlap analyses. The computationally obtained reaction barriers for the initiators support this idea, also. In addition, toxicity tests carried out for PVLs synthesized with acetate complexes containing Sn, Cd and Pb revealed that the Sn and Cd complexes do not have a toxic effect on cell viability at some dilution rates. (C) 2021 Society of Industrial Chemistry., Research Foundation of Ege University, Turkey [2016 FEN 041]; Ege University Planning and Monitoring Coordination of Organizational Development; Ege University Directorate of Library and Documentation, This work was supported by the Research Foundation of Ege University, Turkey (No. 2016 FEN 041). The DFT calculations reported in this study were performed at TUBITAK ULAKBIM, High Performance and Grid Computing Center (TRUBA resources). We are grateful to Ege University Planning and Monitoring Coordination of Organizational Development and the Directorate of Library and Documentation for their support in the editing and proofreading service of this study.

Herein, we describe the synthesis, full spectroscopic characterization, DFT (density functional theory) calculations, and single-crystal X-ray diffraction analyses of a series of osmium arene sigma-germyl, germanate, sigma-stannyl, and stannate complexes, along with their cytotoxic (anticancer) investigations. The known dimer complexes [OsCl2(eta(6)-C6H6)](2) (1) and [OsCl2(eta(6)-p-cymene)](2) (2) were reacted with PPh3 to form the known mononuclear complex [OsCl2(eta(6)-p-cymene)(PPh3)] (3) and the new complex [OsCl2(eta(6)-C6H6)(PPh3)] (6); complex 3 was reacted with GeCl2 center dot(dioxane) and SnCl2 to afford, by insertion into the Os-Cl bond, the neutral sigma-germyl and stannyl complexes [OsCl(eta(6)-p-cymene)(PPh3)(GeCl3)] (7) and [OsCl(eta(6)-p-cymene)(PPh3)(SnCl3)] (11), respectively, as a mixture of enantiomers. Similarly, the reaction of complex 6 with GeCl2 center dot(dioxane) afforded [OsCl(eta(6)-C6H6)(PPh3)(GeCl3)] (9). Complex 2, upon reaction with 1,1-bis(diphenylphosphino)methane (dppm), formed a mixture of [OsCl2(eta(6)-p-cymene)(kappa(1)-dppm)] (4) and [Os(eta(6)-p-cymene)(kappa(2)-dppm)Cl]Cl-+(-) (5) when prepared in acetonitrile and a mixture of 4 and the dinudear complex [[OsCl2(eta(6) -p-cymene)](2) (mu-dppm)] (0) when prepared in dichloromethane. By utilizing either isolated 4 or a mixture of 4 and 5, the synthesis of kappa(2)-dppm germanate and stannate salts, [OsCl(eta(6)-p-cymene)(kappa(2)-dppm)]+GeCl3- (8) and [OsCl(eta(6)-p-cymene)(kappa(2)-dppm)]+SnCl3- (10), were accomplished via halide-abstracting reactions with GeCl2 center dot(dioxane) or SnCl2, respectively. All resulting complexes were characterized by means of multinuclear NMR, FT-IR, ESI-MS, and UV/Vis spectroscopy. X-ray diffraction analyses of 4, 8, 9, 10, and 11 were performed and are reported. DFT studies (B3LYP, basis set LANL2DZ for Os, and def2-TZVPP for Sn, Ge, Cl, P, C, and H) were performed on complex 9 and the benzene analogue of complex 11, 11-benzene, to evaluate the structural changes and the effects on the frontier molecular orbitals arising from the substitution of Ge for Sn. Finally, complexes 3 and 7-11 were investigated for potential anticancer activities considering cell cytotoxicity and apoptosis assays against Dalton's lymphoma (DL) and Ehrlich ascites carcinoma (EAC) malignant cancer cell lines. The complexes were also tested against healthy peripheral blood mononudear cells (PBMCs). All cell lines were also treated with the reference drug cisplatin to draw a comparison with the results obtained from the reported complexes. The study was further corroborated with in silica molecular interaction simulations and a pharmacokinetic study.

The photochemical reduction of carbon dioxide (CO2) into methanol is very appealing since it requires sunlight as the only energy input. However, the development of highly selective and efficient photocatalysts is still very challenging. It has been reported that CO2 can be spontaneously activated on gallium nitride (GaN). Moreover, the photocatalytic activity for CO2 conversion into methanol can be drastically enhanced by incorporating a small amount of Mg dopant. In this work, density functional theory (DFT) based on a cluster model approach has been applied to further explore the photocatalytic activity of bare GaN towards CO2 adsorption and conversion. We extended the investigation of Mg-doping replacing one Ga atom with Mg on three different sites and evaluated the consequent effects on the band gaps and CO2 adsorption energies. Finally, we explore different routes leading to the production of methanol and evaluate the catalytic activity of bare GaN by applying the energetic span model (ESM) in order to identify the rate-determining states which are fundamental for suggesting modifications that can improve the photocatalytic activity of this promising material.

Novel nickel(ii) complexes [Ni(P,P)X2] = [Ni{tBuN(PPh2)2-κ2P}X2], X = Cl, Br, I, are prepared, characterized by IR and NMR spectroscopy, mass spectrometry and X-ray crystallography, and tested as catalysts in the Kumada cross-coupling reaction.

The iron(III) complex [Fe(tpena)]2+ (tpena = N,N,N′-tris(2-pyridylmethyl)ethylendiamine-N′-acetate) undergoes irreversible O2-dependent N-demethylcarboxylation to afford [FeII(SBPy3)(MeCN)]2+ (SBPy3 = N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-aldimine), when irradiated with near-UV light. The loss of a mass equivalent to the glycyl group in a process involving consecutive C-C and C-N cleavages is documented by the measurement of the sequential production of CO2 and formaldehyde, respectively. Time-resolved UV-vis absorption, Mössbauer, EPR, and Raman spectroscopy have allowed the spectroscopic characterization of two iron-based intermediates along the pathway. The first of these, proposed to be a low-spin iron(II)-radical ligand complex, reacts with O2 in the rate-determining step to produce a putative alkylperoxide complex. DFT calculations suggest that this evolves into an Fe(IV)-oxo species, which can abstract a hydrogen atom from a cis methylene group of the ligand to give the second spectroscopically identified intermediate, a high-spin iron(III)-hydroxide of the product oxidized ligand, [FeIII(OH)(SBPy3)]2+. Reduction and exchange of the cohydroxo/water ligand produces the crystallographically characterized products [FeII(SBPy3)(X)]2+/3+, X = MeCN, [Zn(tpena)]+.

Parallel kinetic resolution of racemic mixtures is an important method used in asymmetric synthesis of chiral compounds. In a recent example, a rac-cis-2,3-substituted chiral N-benzoyl aziridine was reacted with dimethyl malonate, in the presence of a La-Y heterobimetallic chiral BINAM Schiff base (L) catalyst, to form enantiomerically pure (ee > 98%) gamma-amino acid derivatives through a ring-opening reaction in near quantitative yields from both the enantiomers (similar to 48%). High regio- and enantioselectivities even with a rac-aziridine, having C2 and C3 substituents as similar as ethyl and n-propyl. Through a comprehensive computational investigation, we delineate the origin of regio-divergent and enantioselective formation of gamma-amino ester derivatives. The Gibbs free energy of the transition state for the ring-opening at the propyl substituted C2 carbon leading to 3-benzamidoheptan-4-yl malonate is found to be 7.2 kcal/mol lower than that at the ethyl substituted C3 carbon in the case of (2R,3S)-aziridine. A reversal of the regio-chemical preference for its enantiomeric (2S,3R)-aziridine is noted where the ring-opening occurs at the ethyl substituted C3 carbon. The La Y catalyst is found to initially "recognize" both the enantiomers of the rac-aziridine rather indiscriminately. The activation barriers for the most-preferred ring-opening for each enantiomer are found to be closely similar, suggesting that both enantiomers would react. The high regio-selectivity in the addition of lanthanum-bound malonate to the aziridine anchored onto the yttrium center is due to a unique geometric disposition of the aziridine in the stereocontrolling ring-opening transition state. The lowest-energy ring-opening transition state for each enantiomer of aziridine exhibited very similar geometries, while notable geometric distortions is identified in the malonate addition to less-preferred site of the same enantiomer.

Recent examples of asymmetric dual chiral catalysis (ADCC), where two chiral catalysts are employed under one-pot reaction conditions, have demonstrated how all stereoisomers of a product could be effectively accomplished 9 through changes in the catalyst chirality. Insufficient 1,1 0,24.1 mechanistic details on the action of two chiral catalysts and molecular insights into the origin of stereodivergence prompted us to undertake a comprehensive density functional theory (B3LYP-D3) investigation on an alpha-allylation reaction of an aldehyde by using an allyl alcohol, resulting in two new chiral centers in the product. The structural and energetic features of the stereocontrolling transition states helped us delineate how all four product stereoisomers could be accessed by using suitable combinations of chiral iridium phosphoramide and diarylprolinol silyl ether in this ADCC reaction. The covalent activation of the pronucleophile (aldehyde) by the organocatalyst furnishes a chiral enamine, whereas the action of the transition metal catalyst (chiral Ir phosphoramidite, P) on racemic allyl alcohol gives the Ir-pi-allyl phosphoramidite complex [IrCl(P)(2)(pi-allyl)], which serves as the electrophilic partner. The enantioselectivity is directly controlled by the sense of axial chirality of the Ir-bound phosphoramidite ligand, which affects whether an R or S stereocenter would be generated at the beta-carbon of the product. The "recognition/interaction" between the two chiral catalysts in the diastereocontrolling C-C bond formation transition states through a series of weak noncovalent interactions (C-H center dot center dot pi, C-H center dot center dot center dot O, C-H center dot center dot center dot Cl, and lone pair center dot center dot center dot pi) is identified as playing a pivotal role in influencing the favorable mode of addition of the si or re face of the chiral enamine to Ir-pi-allyl phosphoramidite (si-si/re-re) and hence controls the chirality at the alpha-carbon atom of the developing product.

Treatment of [RuCl2(DMSO)(4)] with 1-(arylazo)naphthol ligands in benzene under reflux afford the air stable new ruthenium(III) complexes with general composition [Ru(L-R)(3)] (L = bidentate O, N donor; R = H, CH3, OCH3, Br, NO2) in good yield. The 1-(arylazo)naphthol ligands behave as tris-bidentate 0, N donors via naphtholic proton and azo nitrogen. The molecular and electronic structure of the complexes have been established by elemental analysis and spectral (FT-IR, UV-vis & EPR) methods. DFT calculations were also carried out on the complexes 1 and 3 along with X-ray crystallized geometry of complex 5. These complexes in dichloromethane solution show intense ligand-to-metal charge transfer (LMCT) transitions in the visible region. The absorption and g-tensor value of these complexes (1, 3 & 5) were also computed and compared along with the available experimental results. The redox behavior of the complexes has been investigated by cyclic voltammetry and the potentials are observed with respect to the electronic nature of substituents (R) in the 1-(arylazo)naphthol ligands. These complexes have shown great promise as catalysts for the conversion of aldehydes to primary amides in good yield. (C) 2016 Elsevier B.V. All rights reserved.

The halogenation of the C-H bond by metal-oxo-peroxo species and the decarbonylation of aldehydes by metal-peroxo species are performed routinely in biological systems. However, metal-mediated decarbonylative halogenation is unknown in nature. In this work, we have shown that widely available V2O5 and VO(acac)(2) (acac=acetylacetonate) can catalyze decarbonylative halogenation through the generation of an inter-mediate vanadium-oxo-peroxo species, which was characterized by using V-51 NMR, UV/Vis, and resonance Raman spectroscopy. Further detection of formic acid from the reaction mixture confirmed the biomimetic aspects of decarbonylative halogenation. A detailed experimental and DFT study indicated a concerted mechanism for this decarbonylative halogenation performed under simple and mild reaction conditions.

A new class of sparingly soluble NCN palladium(II) pincer complexes of the type (NCN)PdBr:[(Meth-yl)(NCN)PdBr], C26H25N4PdBr (14), [(Tosyl)(NCN)PbBr], (15) [(Benzyl), (NCN)PdBr], C38H33N4PdBr (16) and [(Pentyl)(NCN)PdBr], C34H41N4PdBr (17) [(NCN) = 5-tert-butyl-1,3-bis-(Nsubstituted-benzimidazol-2'-yl)phenyl] were synthesized by the treatment of palladium(0) precursor, Pd-2(dba)(3) with 5-tert-butyl-1,3-bis-(N-substituted-benzimidazol-2'-yl)-2-bromobenzenes (10-13) via oxidative addition with chemical yield of 46-70%. Complex 15 decomposed in [D-6]DMSO to yield the protic palladacycle 18, [H(NCN)PdBr], C24H21N4PdBr, which was confirmed by the time-dependent H-1 NMR studies, IR spectroscopy, mass spectrometry and the structure was corroborated with X-ray crystallographic studies. Complexes 14-18 are the fully characterized examples of NCN palladium(II) pincer complexes incorporating the N-substituted-5-tert-butyl-1,3-bis-(benzimidazol-2'-yl)-2-bromobenzene framework. The palladium(II) pincer complexes have been studied for C-H functionalization of benzyl nitriles with N-tosylaldimines to form beta-aminonitriles. (C) 2018 Elsevier B.V. All rights reserved.

International audience; The synthesis and characterization of a series of arene ruthenium complexes bearing either (3,5-cycloheptadienyl)diphenylphosphine or (cycloheptyl)-diphenylphosphine are reported. Upon irradiation or heating, all these complexes lose their arene ligand but then exhibit a different behavior depending on the nature of the phosphine ligand. (Cycloheptadienyl)phosphine complexes 1 and 3 give a cationic dinuclear Ru complex 5 for which the two Ru atoms are bridged by three chlorido ligands and flanked by two tridendate (cycloheptadienyl)phosphines. (Cycloheptyl)-diphenylphosphine complexes 2 and 4 undergo arene exchange when toluene is used as solvent or degrade in dithloromethane. ATRA catalytic trials conducted in parallel with these complexes using CCl4 and styrene as standard substrates, highlighted the deep impact of the dienyl moiety on the results. Under smooth conditions (UV irradiation or moderate heating), only (cycloheptyl)phosphine derivatives give Karasch adduct in satisfactory yields. Their performance was considerably improved by combining irradiation and heating. At higher temperature, cationic dinuclear complex 5 was revealed as active and robust, giving turnover numbers as high as 9700 when tetradecene and CCl4 were used as substrates.

Iron and manganese ions with terminal oxo and hydroxo ligands are discovered as key intermediates in several synthetic and biochemical catalytic cycles. Since many of these species possess vigorous catalytic abilities, they are extremely transient in nature and experiments which probe the structure and bonding on such elusive species are still rare. We present here comprehensive computational studies on eight iron and manganese oxo and hydroxo (Fe-III/IV/V-O, Fe-III-OH and Mn-III/IV/V-O, Mn-III-OH) species using dispersion corrected (B3LYP-D2) density functional method. By computing all the possible spin states for these eight species, we set out to determine the ground state S value of these species; and later on employing MO analysis, we have analysed the bonding aspects which contribute to the high reactivity of these species. Direct structural comparison to iron and manganese-oxo species are made and the observed similarity and differences among them are attributed to the intricate metal-oxygen bonding. By thoroughly probing the bonding in all these species, their reactivity towards common chemical reactions such as C-H activation and oxygen atom transfer are discussed.

The oxidation chemistry of the simplest conjugated hydrocarbon, 1,3-butadiene, can provide a first step in understanding the role of polyunsaturated hydrocarbons in combustion and, in particular, an understanding of their contribution toward soot formation. On the basis of our previous work on propene and the butene isomers (1-, 2-, and isobutene), it was found that the reaction kinetics of (H) over dot-atom addition to the C=C double bond plays a significant role in fuel consumption kinetics and influences the predictions of high-temperature ignition delay times, product species concentrations, and flame speed measurements. In this study, the rate constants and thermodynamic properties for (H) over dot-atom addition to 1,3-butadiene and related reactions on the (C) over dot(4)H(7) potential energy surface have been calculated using two different series of quantum chemical methods and two different kinetic codes. Excellent agreement is obtained between the two different kinetics codes. The calculated results including zero-point energies, single-point energies, rate constants, barrier heights, and thermochemistry are systematically compared among the two quantum chemical methods. 1-Methylallyl ((C) over dot(4)H(7)1-3) and 3-buten-1-yl ((C) over dot(4)H(7)1-4) radicals and C2H4 + (C) over dot(2)H(3) are found to be the most important channels and reactivity-promoting products, respectively. We calculated that terminal addition is dominant (>80%) compared to internal (H) over dot-atom addition at all temperatures in the range 298-2000 K. However, this dominance decreases with increasing temperature. The calculated rate constants for the bimolecular reaction C4H6 + (H) over dot -> products and C2H4 + (C) over dot(2)H(3) -> products are in excellent agreement with both experimental and theoretical results from the literature. For selected C-4 species, the calculated thermochemical values are also in good agreement with literature data. In addition, the rate constants for H atom abstraction by (H) over dot atoms have also been calculated, and it is found that abstraction from the central carbon atoms is the dominant channel (>70%) at temperatures in the range of 298-2000 K. Finally, by incorporating our calculated rate constants for both (H) over dot atom addition and abstraction into our recently developed 1,3-butadiene model, we show that laminar flame speed predictions are significantly improved, emphasizing the value of this study. This work is supported by the FUELCOM project of Saudi Aramco and by Science Foundation Ireland via their Principal Investigator Program through project number 15/IA/3177. The work at Argonne was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under Contract No. DE-AC02-06CH11357. The authors wish to acknowledge the computational resources provided from the Irish Centre for High-End Computing (ICHEC), under project number ngche043c. We also appreciate the provision of automation Perl code from Dr. Kieran Somers, and MESS_TPfit code from Prof. C. Franklin Goldsmith. peer-reviewed

Recent studies directed to the design of compounds targeting the bc(1) protein complex of Plasmodium falciparum, the parasite responsible for most lethal cases of malaria, identified quinolones (4-oxo-quinolines) with low nanomolar inhibitory activity against both the enzyme and infected erythrocytes. The 4-oxo-quinoline 3-ester chemotype emerged as a possible source of potent bc(1) inhibitors, prompting us to expand the library of available analogs for SAR studies and subsequent lead optimization. We now report the synthesis and structural characterization of unexpected ethyl 6-methyl-7-iodo-4-(3-iodo-4-methylphenoxy)quinoline-3-carboxylate, a 4-aryloxy-quinoline 3-ester formed during attempted preparation of 6-methyl-7-iodo-4-oxo-quinoline-3-carboxylate (4-oxo-quinoline 3-ester). We propose that the 4-aryloxy-quinoline 3-ester derives from 6-methyl-7-iodo-4-hydroxy-quinoline-3-carboxylate (4-hydroxy-quinoline 3-ester), the enol form of 6-methyl-7-iodo-4-oxo-quinoline-3-carboxylate. Formation of the 4-aryloxy-quinoline 3-ester confirms the impact of quinolone/hydroxyquinoline tautomerism, both on the efficiency of synthetic routes to quinolones and on pharmacologic profiles. Tautomers exhibit different cLogP values and interact differently with the enzyme active site. A structural investigation of 6-methyl-7-iodo-4-oxo-quinoline-3-carboxylate and 6-methyl-7-iodo-4-hydroxy-quinoline-3-carboxylate, using matrix isolation coupled to FTIR spectroscopy and theoretical calculations, revealed that the lowest energy conformers of 6-methyl-7-iodo-4-hydroxy-quinoline-3-carboxylate, lower in energy than their most stable 4-oxo-quinoline tautomer by about 27 kJ mol(-1), are solely present in the matrix, while the most stable 4-oxo-quinoline tautomer is solely present in the crystalline phase. Fundacao para a Ciencia e Tecnologia (FCT - Portugal) [UID/Multi/04326/2013]; QREN-COMPETE-UE; CCMAR; FCT [SFRH/BD/81821/2011, RECI/BBB-BQB/0230/2012, UI0313/QUI/2013, UID/FIS/04564/2016]; FEDER/COMPETE-UE; [PTDC/QEQ-QFI/3284/2014 - POCI-01-0145-FEDER-016617] info:eu-repo/semantics/publishedVersion

In the present work we performed a combined experimental and computational study on the interaction of the natural antimalarial endoperoxide plakortin and its synthetic analogue 4a with heme. Obtained results indicate that the studied compounds produce reactive carbon radical species after being reductively activated by heme. In particular, similarly to artemisinin, the formation of radicals prone to inter-molecular reactions should represent the key event responsible for Plasmodium death. To our knowledge this is the first experimental investigation on the reductive activation of simple antimalarial endoperoxides (1,2-dioxanes) by heme and results were compared to the ones previously obtained from the reaction with FeCl2. The obtained experimental data and the calculated molecular interaction models represent crucial tools for the rational optimization of our promising class of low-cost synthetic antimalarial endoperoxides.

Metallic salts as well as protic additives are widely employed in transition metal catalyzed C-H bond functionalization reactions to improve the efficiency of catalytic protocols. In one such example, ZnCl2 and pivalic acid are used as additives in a palladium catalyzed synthesis of isoxazolone from a readily available benzohydroxamic acid under one pot conditions. In this article, we present some important mechanistic insights into the role of ZnCl2 and pivalic acid, gained by using density functional theory (M06) computations. Two interesting modes of action of ZnCl2 are identified in various catalytic steps involved in the formation of isoxazolone. The conventional Lewis acid coordination wherein zinc chloride (ZnCl2 center dot(DMA)) binds to the carbonyl group is found to be more favored in the C-H activation step. However, the participation of a hetero-bimetallic Pd-Zn species is preferred in reductive elimination leading to C-aryl-N bond formation. Pivalic acid helps in relay proton transfer in C-H bond activation through a cyclometallation deprotonation (CMD) process. The explicit inclusion of ZnCl2 and solvent N, N-dimethyl acetamide (DMA) stabilizes the transition state and also helps reduce the activation barrier for the C-H bond activation step. The electronic communication between the two metal species is playing a crucial role in stabilizing the C-aryl-N bond formation transition state through a Pd-Zn heterobimetallic interaction.

Solid-state, thermally stable tetramethylguanidinium N,N-diethylcarbamate [TMGH][O2CNEt2] was prepared from tetramethylguanidine (TMG), N,N-diethylamine and carbon dioxide (1 atm). The reaction of [TMGH][O2CNEt2] with TiCl4 in toluene afforded [TMGH]2[TiCl6] and TiCl2(O2CNEt2)2. The tetrachlorides of titanium, zirconium and hafnium were effectively converted into the respective mixed dichloride-dicarbamates, MCl2(O2CNEt2)2, by the reaction with either silver diethylcarbamate or the corresponding homoleptic metal N,N-diethylcarbamate, M(O2CNEt2)4. The titanium and hafnium derivatives are trinuclear in the solid state according to X-ray diffraction analysis (M = Ti) and DFT calculations (M = Hf). Instead, ZrCl2(O2CNEt2)4 was obtained as a mixture of two isomers presumably holding dinuclear and trinuclear structures, according to DFT calculations. Difluoride-dicarbamate TiF2(O2CNEt2)4 was prepared in a similar way as the homologous Cl-compound. All the products were characterized by analytical and spectroscopic methods, and by X-ray diffraction in the cases of [TMGH]2[TiCl6] and Ti3Cl6(μ-O2CNEt2)6. The complex Hf4Cl4(O)2(O2CNEt2)6[O(CH2)3CHO]2 was isolated in low yield in crystalline form from a thf solution of HfCl2(O2CNEt2)2, and then X-ray characterized.

The reaction of [HFe4(CO)(12)](3) (1) with [Ir(COD)Cl](2) results in the formation of the bimetallic FeIr monohydride carbonyl cluster [HFe4(CO)(12)(IrCOD)](2) (2). This is quantitatively protonated by strong acids to the dihydride [H(2)Fe4(CO)(12)(IrCOD)]- (3). Further addition of acids to 3 results in the tetranuclear dihydride [H2Fe3(CO)(10)(IrCOD)]- (4) via formal oxidative elimination of a Fe(CO)(2) fragment. Compounds 24 have been fully characterized by means of H-1 VT NMR spectroscopy, X-ray crystallography, and DFT calculations. In 2 and 3 the Fe4Ir cluster core adopts a trigonal bipyramidal geometry, while the Fe3Ir core in 4 is tetrahedral. In addition, H-1 VT NMR studies indicate that 2 and 3 are fluxional in solution, whereas 4 is not.

Photolytic reaction of internal acetylenes, RCa parts per thousand CR' (R = Ph, Fc and R' = Ca parts per thousand CPh, Ca parts per thousand CFc, CHO) with iron pentacarbonyl, in presence of CS2, in hexane yields a 3,5-dithiacyclopentene ligand system supported on a Fe-2(CO)(6) framework. On reaction with diacetylenes substituted cis- and trans-3,5-dithiacyclopentene ligand, formed by the coupling of two molecules of the diacetylenes are observed, while, with 3-ferrocenylpropynal, along with coupled 3-ferrocenylpropynal products, cis-3,5-dithiacyclopentene ligand, formed by the coupling of one 3-ferrocenylpropynal and one ferrocenylacetylene is also observed. All compounds have been characterized by IR, H-1 NMR and C-13 NMR spectroscopy, mass spectrometry, and structures of 4a and 4c have been established by single crystal X-ray diffraction technique. In addition, DFT computational analyses of compounds 4a and 4c have been investigated in order to understand the bonding in complexes 4a and 4c.

Organoazides are intermediates in the synthesis of imidometal complexes. Metalimido complexes have an important role in catalysis. Thus, the organoazide interaction with metals is an important issue. However, the isolation of organoazidometal complexes is difficult due to the easy loss of N-2. The present study describes the complexation of nickel by nitrobenzyl azides by means of electrospray ionization mass spectrometry (ESI-MS), which was used also as a probe for the characterization of isomers. Organoazidometal complexes were observed and isolated from solutions of NiCl2 and NiBr2 in methanol/water. A different solvent, ethanol/water was also used. The complexes detected were singly and doubly positively charged, with various stoichiometries. The most abundant species were [Ni(II)Az(3)](2+) for ortho- and para-isomers, and [Ni(II)Az(3)(H2O)](2+) for meta isomer, where Az stands for nitrobenzyl azides. The ortho isomer showed several single positively charged complexes integrating chloride as a ligand. The mass spectra of the three isomers allowed their differentiation based on different behaviour in the mass range m/z 296 m/z 312. The MS2 spectra of [Ni(II)Az(3)](2+) were investigated aiming to characterize the three isomers but this analysis was not absolutely conclusive about the coordination site(s). Density functional theory calculations provided possible structures for the [Ni(II)Az(3)](2+) cation with the different isomers and their coordination modes could be responsible for their fragmentation pathways. (C) 2013 Elsevier B.V. All rights reserved.

The 1 : 1 molar reactions of niobium and tantalum pentahalides with the monodentate NHC ligand 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (Ipr), in toluene (or benzene) at ca. 80 °C, afforded the complexes NbX5(Ipr) (X = F, 2; Br, 3) and TaX5(Ipr) (X = F, 4; Cl, 5; Br, 6), in generally good yields. Complexes 2–6 represent uncommon cases of stable NHC adducts of metal halides with the metal in an oxidation state higher than +4, and also rare examples of Nb–NHC and Ta–NHC bonding systems. In particular, the X-ray molecular structure determined for 6 provides the unprecedented crystallographic characterization of a tantalum compound with a monodentate NHC ligand. DFT results indicate that the metal–carbon bond in 2–6 is a purely σ one. According to NMR studies (1H, 13C, 93Nb), the formation of 3, 5, 6, as well as the previously communicated NbCl5(Ipr), 1, proceeded with the intermediacy of [MX6]− salts, presumably due to steric reasons. On the other hand, the intermediate formation of MF6− in the pathways to 2 and 4 was not observed, according to 19F (and 93Nb in the case of 2) NMR. DFT calculations were carried out in order to shed light on structural and mechanistic aspects, and allowed to trace possible reaction routes.

The generation, under self-assembly conditions, of coordination polymers on surface based combinations of a terpyridine–antracene–pyridine based tecton and Co(II) or Pd(II) cations is primarily governed by the coordination geometry of the metal center (octahedral and square planar respectively). While the octahedral Co(II) based polymer self-assembles in insulating films exhibiting randomly oriented crystalline domains, the planarity of Pd(II) based polymers leads to the formation of conductive π–π stacked fibrillar structures exhibiting anisotropically oriented domains. In the latter case, the favorable Pd–Pd and anthracene–anthracene wavefunction overlaps along the fiber direction are responsible for the large electronic couplings between adjacent chains, whereas small electronic couplings are instead found along individual polymer chains. These results provide important guidelines for the design of conductive metal coordination polymers, highlighting the fundamental role of both intra- as well as inter-chain interactions, thus opening up new perspectives towards their application in functional devices.