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The synthesis of heteroleptic monomeric cationic Rh(I) bis-diphosphine complex [Rh(dppe)(dppp)]Cl (dppe = 1,2-bis-(diphenylphosphino)ethane and dppp = 1,3-bis-(diphenylphosphino)propane) was achieved by reaction between the neutral dimeric complex [Rh2(dppe)2(μ2-Cl)2] and the dppp ligand. The corresponding complex [Rh(dppe)(dppp)]BF4 was instead obtained from reaction between [Rh(dppe)(nbd)]BF4 (nbd = bicyclo-[2.2.1]-hepta-2,5-diene) and the dppp ligand. Previous protocols had extended to the synthesis of the analogous homoleptic complexes containing two dppe or two dppp ligands. The structural analysis of such complexes conducted in the solid state by single-crystal x-ray crystallography and in solution by 31P and 1H NMR revealed a distorted square planar geometry where the anion and the cation are not bonded each other. Nevertheless, important differences in reactivity can be found if same complexes with different anions are compared, as in the case of the phosphine exchange reaction between [Rh(dppp)2]X (X = Cl−, BF4−) and the dppe ligand or in the case of the employment of such complexes as catalytic precursors for the transfer hydrogenation reaction from 2-propanol to acetophenone.

Three ternary mixtures composed by choline chloride (ChCl), ethylene glycol (EG), and a second hydrogen bond donor (HBD) as ethanol (A), 2-propanol (B), and glycerol (C) were studied in terms of composition related to the band gap energy (BGE). A Design of Experiments (DoE) approach, and in particular a Simple Lattice three-components design, was employed for determining the variation of the BGE upon the composition of each system. UV-VIS analysis and subsequent Tauc plot methodology provided the data requested from the DoE, and multivariate statistical analysis revealed a drop of the BGE in correspondence to specific binary compositions for systems A and B. In particular, a BGE of 3.85 eV was registered for the mixtures ChCl/EtOH (1:1) and ChCl/2-propanol (1:1), which represents one of the lowest values ever observed for these systems.

The selective formation of the heterocyclic salt ((1,4-dioxane-2,5-diyl)-bis-(methylene))-bis-(triphenylphosphonium) chloride was observed when epichlorohydrin and triphenylphosphine were reacted in CH2Cl2 at room temperature. Slow evaporation from a mixture of ethanol and ethyl acetate allows to isolate monocrystals of the heterocyclic phosphonium salt. Mechanistic investigations point to the formation of the zwitterionic intermediate 1-chloro-3-(triphenylphosphonio)-propan-2-olate, which can dimerize and generate the 1,4-dioxane derivative. In the exclusive presence of a Brønsted acid as HCl, which usually facilitates epoxide ring opening, the exclusive formation of 1,3-dichloro-2-propanol was although observed. Also, when epichlorohydrin, PPh3, and a stoichiometric amount of HCl were mixed, (2-chloro-3-hydroxypropyl)-triphenylphosphonium chloride was formed and its isolation in pure form provides monocrystals subjectable to X-ray analysis.

Deep Eutectic Systems (DESs) are obtained by combining Hydrogen Bond Acceptors (HBAs) and Hydrogen Bond Donors (HBDs) in specific molar ratios. Since their first appearance in the literature in 2003, they have shown a wide range of applications, ranging from the selective extraction of biomass or metals to medicine, as well as from pollution control systems to catalytic active solvents and co-solvents. The very peculiar physical properties of DESs, such as the elevated density and viscosity, reduced conductivity, improved solvent ability and a peculiar optical behavior, can be exploited for engineering modular systems which cannot be obtained with other non-eutectic mixtures. In the present review, selected DESs research fields, as their use in materials synthesis, as solvents for volatile organic compounds, as ingredients in pharmaceutical formulations and as active solvents and cosolvents in organic synthesis, are reported and discussed in terms of application and future perspectives.

The employment of easily affordable ruthenium(II)-complexes as pre-catalysts in the transfer hydrogenation of carbonyl compounds in deep eutectic media is described for the first time. The eutectic mixture tetrabutylammonium bromide/formic acid = 1/1 (TBABr/HCOOH = 1/1) acts both as reaction medium and hydrogen source. The addition of a base is required for the process to occur. An extensive optimization of the reaction conditions has been carried out, in terms of catalyst loading, type of complexes, H2-donors, reaction temperature and time. The combination of the dimeric complex [RuCl(p-cymene)-μ-Cl]2 (0.01–0.05 eq.) and the ligand dppf (1,1′-ferrocenediyl-bis(diphenylphosphine)ferrocene) in 1/1 molar ratio has proven to be a suitable catalytic system for the reduction of several and diverse aldehydes and ketones to their corresponding alcohols under mild conditions (40–60 °C) in air, showing from moderate to excellent tolerability towards different functional groups (halogen, cyano, nitro, phenol). The reduction of imine compounds to their corresponding amine derivatives was also studied. In addition, the comparison between the results obtained in TBABr/HCOOH and in organic solvents suggests a non-innocent effect of the DES medium during the process.

Films with different morphology can be obtained by mixing fish gelatin, Tara gum and glycerol in different ratio and by subjecting the Tara gum to a ball milling treatment before its use. The amount of the plasticizer glycerol, as well as the type of Tara gum employed (as received or milled) resulted, from SEM and AFM analyses, to strong influencing the morphology of the films and their density. Also, the morphological differences determine different thermal and mechanical behaviours. In particular, the employment of milled Tara gum allows to improve the thermal stability, as well as the mechanical properties of the polymers. A similar outcome can be obtained by increasing the glycerol content, which can be used up to 20 wt%. Glycerol amounts exceeding that percentage, are detrimental for the quality of the films and reduce their thermal and mechanical performances., FEDER (Fondo Europeo de Desarrollo Regional) and both the Spanish Agencia Estatal de Investigacióon (MAT2017–84501-R; MAT2017-88923-P) and the Consejería de Educación, Junta de Castilla y León (BU306P18)

The unprecedented Nazarov cyclization of a model divinyl ketone using phosphonium-based Deep Eutectic Solvents as sustainable non-innocent reaction media is described. A two-level full factorial Design of Experiments was conducted for elucidating the effect of the components of the eutectic mixture and optimizing the reaction conditions in terms of temperature, time, and substrate concentration. In the presence of the Deep Eutectic Solvent (DES) triphenylmethylphosphonium bromide/ethylene glycol, it was possible to convert more than 80% of the 2,4-dimethyl-1,5-diphenylpenta-1,4-dien-3-one, with a specific conversion, into the cyclopentenone Nazarov derivative of 62% (16 h, 60 &deg, C). For the reactions conducted in the DES triphenylmethylphosphonium bromide/acetic acid, quantitative conversions were obtained with percentages of the Nazarov product above 95% even at 25 &deg, C. Surface Responding Analysis of the optimized data furnished a useful tool to determine the best operating conditions leading to quantitative conversion of the starting material, with complete suppression of undesired side-reactions, high yields and selectivity. After optimization, it was possible to convert more than 90% of the model substrate into the desired cyclopentenone with cis percentages up to 77%. Experimental validation of the implemented model confirmed the robustness and the suitability of the procedure, leading to possible further extension to this specific combination of experimental designs to other substrates or even to other synthetic processes of industrial interest.

An integrated approach, based on quantitative transmission mode powder X-ray diffraction (PXRD) combined with multivariate statistical analysis, has been applied to cellulose obtained from three different sources to correlate the mercerization degree and crystallinity with the cellulose type, temperature, and reaction time. The effects of the experimental conditions on the two outcomes were studied by design of experiments (DoE) and surface responding analysis (SRA) combined with principal component analysis (PCA). SRA showed a marked influence of the type of cellulose (wood cellulose from the kraft vs. sulfite process, WCK vs. WCS) on the conversion of cellulose I to cellulose II (CII%) during mercerization. A counterintuitive simultaneous effect of temperature and cellulose type was also highlighted. The data elaboration in the form of response surface plots provided an easy predictive tool for the optimum conditions to maximize the conversion. The simulation reported for WCK showed maximum conversion (96%) at 70 &deg, C in 24 h with 18%wt NaOH.

UV&ndash, VIS spectroscopy analysis of six mixtures containing choline chloride or triphenylmethylphosphonium bromide as the hydrogen bond acceptor (HBA) and different hydrogen bond donors (HBDs, nickel sulphate, imidazole, d-glucose, ethylene glycol, and glycerol) allowed to determine the indirect and direct band-gap energies through the Tauc plot method. Band-gap energies were compared to those relative to known choline chloride-containing deep band-gap systems. The measurements reported here confirmed the tendency of alcohols or Lewis acids to increment band-gap energy when employed as HBDs. Indirect band-gap energy of 3.74 eV was obtained in the case of the triphenylmethylphosphonium bromide/ethylene glycol system, which represents the smallest transition energy ever reported to date for such kind of systems.

The optical properties of nine choline-based Deep Eutectic Solvents (DESs) of the type choline+X− (X− = chloride or acetate)/Y (Y = ethylene glycol, glycolic or levulinic acid) were studied by measuring their band gap through the UV-VIS-based Tauc method. All the considered systems showed a direct optical transition. A correlation between band gap and eutectic composition was discovered by plotting the variation of the band gap versus the molar fraction of choline+X−/Y in the parent systems containing 10 wt% of H2O. The main parameters influencing the energy of the optical transition in these “Deep Band Gap Systems” (DeBaGS) where studied through Design of Experiments (DoE) combined with multivariate analysis. The effect on the band gap of the anion (chloride or acetate), the acid (levulinic or glycolic), the water, and the stirring time, considered as single factor or in combination was clarified. Thus a multivariate model was implemented through surface responding analysis which allows engineering such kind of systems and opening to further applications in material science.

The reduction of ketones through homogeneous transfer hydrogenation catalyzed by transition metals is one of the most important routes for obtaining alcohols from carbonyl compounds. The interest of this method increases when opportune catalytic precursors are able to perform the transformation in an asymmetric fashion, generating enantiomerically enriched chiral alcohols. This reaction has been extensively studied in terms of catalysts and variety of substrates. A large amount of information about the possible mechanisms is available nowadays, which has been of high importance for the development of systems with excellent outcomes in terms of conversion, enantioselectivity and Turn Over Frequency. On the other side, many mechanistic aspects are still unclear, especially for those catalytic precursors which have shown only moderate performances in transfer hydeogenation. This is the case of neutral [RuCl2(η6-arene)(P)] and cationic [Rh(PP)2]X (X = anion; P and PP = mono- and bidentate phosphine, respectively) complexes. Herein, a summary of the known information about the Transfer Hydrogenation catalyzed by these complexes is provided with a continuous focus on the more relevant mechanistic features.

A pulsed gradient spin echo experiment on [Rh2(1,3-bis-(diphenylphosphino)-propane)2(μ2-Cl)2] complex has been conducted in order to shed light on the supposed monomerisation process of [Rh2(diphosphine)2(μ2-Cl)2] complexes in solution. Such a process should generate a 14-electron [Rh(diphosphine)Cl] complex, which has only been postulated to date. Metathesis experiments on [Rh2(1,3-bis-(diphenylphosphino)-propane)2(μ2-Cl)2] and [Rh2(bis[2-(diphenylphosphino)phenyl]ether)2(μ2-Cl)2] complexes, analysed by 31P NMR, reveal that monomerisation of [Rh2(diphosphine)2(μ2-Cl)2] complexes is not restricted to the case of 1,3-bis-(diphenylphosphino)propane.

An unexpected reaction of pyridine with acetyl chloride to give N-acetyl-1,2 and 1,4-dihydropyridyl acetic acid (1, 2) in high yield and regioselectivity has been reported. The key step is the formation of a zwitterionic pyridinium ketene enolate. The effect of different activating agents on the reaction yield and selectivity has been studied. Platinum(IV) mediated hydrogenation of the corresponding methyl esters (7, 8) gave piperidine derivatives (9, 10). © 2014 Elsevier Ltd. All rights reserved.

The regioselectivity of the reaction can be altered by choice of the activating agent: NaH for 1,2- or TMS-O-Tf for 1,4-selectivity.

A family of eight neutral, pseudotetrahedral piano-stool ruthenium complexes C, of the type [RuCl2(p-cymene)(PArPhR)] (Ar = 1-naphthyl, 9-phenanthryl and 2-biphenylyl; R = Me, i-Pr, OMe, –CH2SiMe3 and –CH2SiPh3) have been prepared and characterised, including the X-ray crystal structure for C6 (Ar = 2-biphenylyl; R = i-Pr). These complexes catalyse the asymmetric hydrogen transfer reaction of acetophenone in refluxing 2-propanol in the presence of potassium tert-butoxyde, reaching full conversions and up to 45% ee after 24 h towards the S enantiomer of 1-phenylethanol. Cationic complexes formed upon treatment of C with one equivalent of AgSbF6 or (Et3O)PF6 are active in the cyclopropanation reaction of styrene and α-methylstyrene by ethyl diazoacetate. Low to moderate conversions (up to 58%), diastereoselectivities (up to 40% de), and moderate enantioselectivities (up to 69% ee) have been found. For both reactions, bulky complexes and C6 in particular lead to the best results.

Two groups of P-stereogenic monodentate phosphines containing pendant groups bearing functionalities capable of having secondary interactions, PArPhR (Ar = 2-[(2′,6′-dimethoxy)-1,1′-biphenylyl] and R = OMe (6) or Me (8)) and PMeR(CH2R′) (13, R = t-Bu or 14 R = Fc and R′ = SiMe3 (a), SiMe2Ph (b) or CH2(2-naphthyl) (c)) have been prepared in enantiomerically pure form by the Juge and Evans methodologies and characterised, including the crystal structure for the borane adduct of 12b. Reaction of the phosphines with the Pd dimer [Pd(η3-2-Me-allyl)(μ-Cl)]2 produced neutral allylic complexes C [PdCl(η3-2-Me-C3H4)P∗], which have been characterised in solution and shown to be a mixture of isomers with different absolute configuration at the Pd atom. After abstraction of the chloride ligand by AgBF4, the solutions of cationic complexes have been used as catalyst precursors in the hydrovinylation of styrene under mild conditions. Very good activities (up to 1015 h−1), moderate to good selectivities to 3-phenyl-1-butene and low to moderate enantioselectivities (