Mechanistic Studies of Ethylene Hydrophenylation Catalyzed by Bipyridyl Pt(II) Complexes

This article discusses mechanistic studies of ethylene hydrophenylation catalyzed by bipyridyl Pt(II) complexes

Specie esotiche invasive di rilevanza unionale in Italia: aggiornamenti e integrazioni

La Commissione Europea (CE) ha inserito ad oggi 36 taxa esotici vegetali nella lista delle specie esotiche invasive di rilevanza unionale ai sensi del Regolamento (UE) n. 1143/2014 del Parlamento Europeo e del Consiglio, recante disposizioni volte a prevenire e gestire l’introduzione e la diffusione delle specie esotiche invasive. La lista delle specie di rilevanza unionale viene periodicamente aggiornata e include quelle specie che rappresentano una grave minaccia per la biodiversità, ma anche per la salute dei cittadini e le attività economiche nei territori dell’Unione Europea e che necessitano di una gestione concertata a livello comunitario. La CE vigila sullo stato di ogni taxon grazie anche a periodiche rendicontazioni da parte dei paesi dell'Unione. In vista di tali report, tra il 2020 e il 2021 è stata definita e integrata la distribuzione di queste specie in Italia

Structural properties of the metallointercalator cationic complex (2,2 ': 6 ',2 ''-terpyridine)methylplatinum(II) ion

The complex [Pt(tpy)(Me)](+) (BPh4)(-) (tpy = 2,2':6',2 "-terpyridine) crystallizes in the triclinic space group with a = 13.463(2) Angstrom, b = 13.618(3) Angstrom, c = 20.151(4) Angstrom, alpha = 73.59(2), beta = 74.56(3), gamma = 65.82(2)degrees and Z = 4. The final conventional R factor is 0.035. In the unit cell a couple of weakly interacting dimers are formed by stack of two [Pt(tpy)(Me)](+) cations in a head-to-tail fashion with intermolecular Pt ... Pt distances of 4.437(1) and 4.931(1) Angstrom, respectively. The absorption spectra of [Pt(tpy)(Me)](+) (BPh4)(-) in acetonitrile show bands assigned to pi-pi* and to MLCT transitions. The analysis of the dependence of the spectra on complex concentration gives a fairly low value for the dimerization equilibrium constant (K-d = 180 +/- 52 M-1 at 298 K). These fluid solutions are not emissive. The room-temperature solid-state emission spectra of the salts [Pt(tpy)(Me)]X are strongly dependent on the counterion (X = BPh4-, Cl-, PF6-, ClO4-, CF3SO3-). The cationic complex shows a considerable stability upon acidification and carbonilation in water

Structural Properties and Dissociative Fluxional Motion of 2,9-Dimethyl-1,10-Phenanthroline in Platinum(II) Complexes

A dynamic H-1 NMR study has been carried out on the fluxional motion of the symmetric chelating ligand 2,9-dimethyl-1,10-phenanthroline(Me-2-phen) between nonequivalent exchanging sites in a variety of square-planar complexes of the type [Pt(Me)(Me-2-phen)(PR3)]BArf, 1-14,(BArf = B[3,5-(CF3)(2)C6H3](4)). In these compounds, the P-donor ligands PR3 encompass a wide range of steric and electronic characteristics [PR3 = P(4-XC6H4)(3), X = H 1, F, 2, Cl 3, CF3 4, MeO 5, Me 6; PR3 = PMe(C6H5)(2) 7, PMe2(C6H5) 8, PMe3 9, PEt3 10,P(i-Pr)(3) 11, PCY(C6H5)(2) 12, PCy2(C6H5) 13, PCy3 14]. All complexes have been synthesized and fully characterized through elemental analysis, H-1 and P-31{H-1} NMR. X-ray crystal structures are reported for the compounds 8, 11, 14, and for Pt(Me)(phen)(P(C6H5)(3))]PF6 (15), all but the last showing loss of planarity and a significant rotation of the Me2-phen moiety around the N1-N2 vector. Steric congestion brought about by the P-donor ligands is responsible for tetrahedral distortion of the coordination plane and significant lengthening of the Pt-N-2 (cis to phosphane) bond distances. Application of standard quantitative analysis of ligand effects (QALE) methodology enabled a quantitative separation of steric and electronic contributions of P-donor ligands to the values of the platinum-phosphorus (1)J(PtP) coupling constants and of the free activation energies DeltaG(double dagger) of the fluxional motion of Me2-phen in 1-14. The steric profiles for both (1)J(PtP) and DeltaG(double dagger) show the onset of steric thresholds (at cone angle values of 150degrees and 148degrees, respectively), that are associated with an overload of steric congestion already evidenced by the crystal structures of 11 and 14. The sharp increase of the fluxional rate of Me-2-phen can be assumed as a perceptive kinetic tool for revealing ground-state destabilization produced by the P-donor ligands. The mechanism involves initial breaking of a metal-nitrogen bond, fast interconversion between two 14-electron three-coordinate T-shaped intermediates containing)eta(1)-coordinated Me-2-phen, and final ring closure. By use of the results from QALE regression analysis, a free-energy surface has been constructed that represents the way in which any single P-donor ligand can affect the energy of the transition state in the absence of aryl or pi-acidity effects

Development of a Nitrazine Yellow-glycidyl methacrylate coating onto cotton fabric through thermal-induced radical polymerization reactions: a simple approach towards wearable pH sensors applications

In this paper, the bifunctional monomer glycidyl methacrylate (GMA) was employed in a simple two-step synthetic strategy with the aim of developing a Nitrazine Yellow-based pH-meter wearable sensor. The catalyzed epoxy ring-opening of GMA allowed the formation of a covalent bond with the sulfonate groups of the halochromic dyestuff, while potassium persulfate thermally initiated the radical grafting of the functionalized NY onto cellulose. Both reactions have been confirmed by Nuclear Magnetic Resonance Spectroscopy and by Infrared Spectroscopy, respectively. Furthermore, the morphology of the treated cotton samples was studied by means of Scanning Electron Microscopy. The pH-halochromic behaviour of the functionalized NY molecule was studied both in solution and onto the fabrics, by means of UV–Vis Spectroscopy, UV–Vis reflectance measurements and CIELAB colour changes. All experimental findings confirmed that the immobilized NY dyestuff still pertains consistent and typical halochromic properties in the pH range 6.0–7.0. The novel functional fabric developed in this work paves the way to non-disposable and reversible wearable pH sensors in smart textiles. Graphic abstract: [Figure not available: see fulltext.

Ligand exchange and substitution at platinum(II) complexes: evidence for a dissociative mechanism

Square-planar complexes of the type cis-[Pt(Me)2(Me2SO)(PR3)] (1–6) where PR3 represents a series of isosteric tertiary phosphanes [P(4-MeOC6H4)3, P(4-MeC6H4)3, P(C6H5)3, P(4-FC6H4)3, P(4-ClC6H4)3, P(4-CF3C6H4)3] have been synthesised and fully characterised through elemental analysis, 1H and 31P{1H} NMR. The coupling constants 1JPtP with the isotopically abundant 195Pt (33%, I=1/2) of 1–6, as those of the pyridine cis-[Pt(Me)2(py)(PR3)] derivatives (7–12), show linear dependencies on the basicity of the coordinated phosphane. The rates of dimethyl sulfoxide exchange for all the complexes have been measured at relatively low temperatures by 1H NMR isotopic labelling experiments with deuterated chloroform as the solvent. Pyridine for dimethyl sulfoxide substitution has been studied at higher temperatures through conventional spectrophotometric techniques. The rates of both processes show no dependence on ligand concentration, for each complex the value of the rate of ligand substitution is in reasonable agreement with the value of the rate of ligand exchange at the same temperature, and the kinetics are characterised by largely positive entropies of activation. There is a compensation-effect between ΔH‡ and ΔS‡, i.e., a greater ΔH‡ is accompanied by a larger positive ΔS‡, indicating that all complexes react via the same mechanism. The basicity of the phosphane does not affect significantly the reaction rates. The general pattern of behaviour indicates that the rate determining step for substitution is the dissociation of the sulfoxide ligand and the formation of a three-coordinated [Pt(Me)2(PR3)] uncharged intermediate

Platinum(II) Complexes Bearing 1,1'-bis(diphenylphosphino)ferrocene as Building Blocks for Functionalized Redox Active Porphyrins

Reactions of the cationic complex ions [PtMe(Me2SO)(PP)]+ (PP = dppf (1,1-bis(diphenylphosphino)ferrocene) and dppe (1,2-bis(diphenylphosphino)ethane)) with 5,10,15,20-tetrakis(4-pyridyl)-21H,23H-porphyrin (TpyP) led to the formation of the symmetrical tetraplatinated porphyrin complexes, [PtMe(PP)]4TpyP·X4 (PP = dppf, X = CF3SO3 −, 3, and PP = dppe, X = BF4 −, 5) containing the organometallic fragment {PtMe(PP)}. The precursor sulfoxide platinum complexes [PtMe(Me2SO)(dppf)]CF3SO3, 2 and [PtMe(Me2SO)(dppe)]BF4, 4, were prepared by halide abstraction from [PtMeCl(dppf)], 1, and by controlled protonolysis of [PtMe2(dppe)] respectively, in the presence of a small amount of dimethyl sulfoxide. All these starting platinum(II) compounds, as well as the porphyrin derivatives 3 and 5, were fully characterized through elemental analysis, 1H NMR mono- and bidimensional, 31P{1H}, 31P–1H HMBC, UV/Vis absorption and photophysical measurements. The X-ray crystal structure of complex 1 has been determined. In order to ascertain the electronic influence of ferrocene, the spectroscopic and redox properties of 3 were compared with those of TPyP and of the analogous 5. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), 1H and 31P NMR data, and UV/Vis data, all suggest a certain degree of communication between the central porphyrin and the peripheral hetero-bimetallic fragments. In contrast, no detectable interaction among these peripheral groups seem to come into play. Unlikely from the porphyrin derivative 5, formation of well defined fluorescent mesoscopic ring structures was easily achieved by simple evaporation from diluted dichloromethane solutions of 3