Transition Metal Chemistry

Current research reports and chronological list of recent articles.


Transition Metal Chemistry is an international scientific journal dealing with all aspects of the preparation of transition metal-based compounds of all kinds, their structural, physical, kinetic and biological properties, their use in chemical synthesis as well as their application in the widest context, their role in naturally occurring systems and more.

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Transition Metal Chemistry - Abstracts



A comparative study of the electrochemical and proton-reduction behaviour of diphosphine-dithiolate complexes [M 2 (CO) 4 (μ-dppm){μ-S(CH 2 ) n S}] (M = Fe, Ru; n  = 2, 3)

Abstract

The electrochemistry of dppm-bridged dithiolate complexes [M2(CO)4(μ-dppm){μ-S(CH2) n S}] (M = Fe, Ru; n = 2, 3) has been studied by cyclic voltammetry. The diiron complexes show similar electrochemical responses in CH2Cl2 but differ significantly in MeCN, while the diruthenium complexes change only slightly with changes in the dithiolate backbone and solvent. Proton-reduction studies in MeCN with HBF4·Et2O as the proton source show that all are active catalysts for proton reduction in their singly reduced state. An additional catalytic event is observed for all, resulting from their partial protonation giving [M2(CO)4(μ-dppm){μ-S(CH2) n S}(μ-H)][BF4]. The diiron complexes show better long-term stability to acids, the diruthenium complexes degrading at high acid concentrations.

Graphical Abstract

The electrochemical response of dithiolate complexes [M2(CO)4(μ-dppm){μ-S(CH2) n S}] (M = Fe, Ru; n = 2, 3) has been investigated in different solvents as well as they have been tested as electrocatalysts for the reduction of protons to hydrogen.


Datum: 01.10.2017


Syntheses, crystal structures, electrochemical and photocatalytic properties of two mixed-ligand cobalt(II) coordination polymers based on flexible bis(2-methylbenzimidazole) dicarboxylic acid ligands

Abstract

Two Co(II) coordination polymers (CPs), namely [Co(L)(tp)] n (1) and [Co(L)0.5(tbip)·H2O] n (2), (L = 1,6-bis(2-methylbenzimidazolyl) hexane, H2tp = terephthalic acid, H2tbip = 5-tert-butyl isophthalic acid), were hydrothermally synthesized and characterized by physicochemical and spectroscopic methods. CP 1 possesses a 2D (4,4) corrugated layer structure, which further extends into a 3D supramolecular framework by π–π stacking interactions, while CP 2 has a 1D ladder-like chain structure and combines into a 2D layer via O–H⋯O hydrogen-bonding interactions. The thermal stabilities, luminescence and electrochemical properties of both CPs, as well as photocatalytic activities for the decomposition of methylene blue, were presented. The photocatalytic mechanism was investigated by introducing t-butyl alcohol, EDTA-2Na and benzoquinone as OH, (hole)+ and ·O2− scavengers, respectively.


Datum: 01.10.2017


An azide-bridged copper(II) 1D-chain with ferromagnetic interactions: synthesis, structure and magnetic studies

Abstract

A coordination polymer of formula [Cu(μ 1,3-N3)2(imH)2] n (1) has been synthesized by reaction of Cu(NO3)2 with imidazole and sodium azide in CH3OH/CH3CN. The complex was characterized by FTIR, elemental analysis, powder diffraction, thermogravimetric analysis, magnetic measurements, and single-crystal X-ray diffraction. The X-ray crystal structure shows that the Cu(II) centers have a distorted octahedral coordination geometry, being coordinated by two imidazole ligands at the trans positions. Each azide links two [Cu(imH)2]2+ units to form 1D zigzag chains. Variable-temperature magnetic susceptibility studies at low field reveal dominant intrachain ferromagnetic/antiferromagnetic interactions. Using a model with n = 10, the coupling parameters J AF = −2.95 and J F = 17.99 with g = 2.12 have been determined.


Datum: 01.10.2017


Dynamic in situ solvothermal reactions between ZnX 2 (X = Cl, ClO 4 ) and a heterocyclic disulfide

Abstract

Solvothermal reactions of 2-ppds (2-ppds = di[4-(pyridin-2-yl)pyrimidinyl]disulfide) with ZnX2 (X = Cl, ClO4) in mixed CH3OH–CH2Cl2 solvent have been investigated. To better understand these reactions, solution analysis was conducted in parallel with single-crystal X-ray diffraction analysis of the in situ generated coordination complexes. At 120 °C, solvothermal reaction of 2-ppds with ZnCl2 resulted in a discrete mononuclear coordination complex formulated as [ZnCl2(L1)] (1), in which the zwitterion L1 (1-methyl-4-(pyridin-2-yl)pyrimidin-1-ium-2-olate) was formed in situ from 2-ppds, and solution analyses based on TLC and ESI–MS further showed that the reaction solution also contains in situ transformed products of L2 (bis(4-(pyridin-2-yl)pyrimidin-2-yl)sulfane) and L3 (2-methoxy-4-(pyridin-2-yl)pyrimidine). At 90 °C, solvothermal reaction between 2-ppds and Zn(ClO4)2 led to a discrete mononuclear coordination complex formulated as [Zn(SH)(L2)]ClO4 (2) that features a terminally bound –SH group, while the reaction solution was also found to contain a library of in situ reaction products of 2-ppds including L1, L2, L3 and L4 ((4-(pyridin-2-yl)pyrimidin-2-yl) 4-(pyridin-2-yl)pyrimidine-2-sulfonothioate). Thus, the heterocyclic disulfide 2-ppds is transformed in situ into various organic products in a series of reactions involving C–S/S–S bond cleavage.


Datum: 01.10.2017


Oxidation in vitro of chromium(III) dietary supplements mer -[Cr(pic) 3 ] and trans (S,S)-[Cr(Cys) 2 ] − by hydrogen peroxide

Abstract

Biological tests performed using 3T3 fibroblasts indicated low cytotoxicities for the complexes mer-[Cr(pic)3] and trans(S,S)-[Cr(Cys)2], where pic = picolinate anion and Cys = cysteine. Oxidation of these complexes by hydrogen peroxide was studied in NaOH and NaHCO3 media. Electronic (UV–Vis) and EPR spectroscopies were used to monitor the reaction course. Hydrogen peroxide oxidizes chromium(III) to both [CrV(O2)4]3− and CrVIO4 2− anions in alkaline media and practically completely to CrO4 2− anion in bicarbonate solution. The reactions follow consecutive biphasic or simple first-order kinetics. The first-order decay of [CrV(O2)4]3− anion at pH ≈ 8 was followed by EPR spectroscopy. Based on the obtained kinetic and spectroscopic data, mechanisms for the redox transformations of these chromium(III) complexes are proposed.


Datum: 01.10.2017


Synthesis, characterization and electrocatalytic performance of a cobalt(II) complex of N -phenylpyridin-2-ylmethanimine

Abstract

N-phenylpyridin-2-ylmethanimine, HL reacts with CoBr2 to afford a water-soluble cobalt(II) complex [CoII(HL)2Br2] 1, whose crystal structure has been determined by X-ray diffraction. Electrochemical studies show that this complex can electrocatalyze hydrogen generation from a neutral buffer with a turnover frequency (TOF) of 875.17 mol of hydrogen per mole of catalyst per hour (mol H2/mol catalyst/h) at an overpotential (OP) of 837.6 mV. Compared with the cobalt complex 1, the previously described nickel(II) complex [Ni(HL)2Cl2] (970.45 mol H2/mol catalyst/h at an OP of 837.6 mV) exhibits more efficient activity for hydrogen evolution.


Datum: 01.10.2017


A nickel(II) thiosemicarbazonato complex: synthesis, structure, electrochemistry, and application in catalytic coupling of terminal alkynes with arylboronic acids

Abstract

A simple route for the synthesis of a new square-planar nickel(II) complex of 2-((3-methylthiophen-2-yl)methylene)hydrazinecarbothioamide is described. Elemental analysis, solution conductivity, and spectral measurements were used to authenticate the composition of the complex. In addition, the X-ray crystal structure of the complex was obtained. Each of the two ligands of the centrosymmetric structure is coordinated to the metal center via the azomethine N and the thioimidate S atoms, forming five-membered chelate rings. Infrared and NMR spectroscopic features of the complex are consistent with its molecular structure. The complex displays a quasi-reversible reduction with E 1/2 of −0.83 V (ΔE p 160 mV), indicating that the ligand system can stabilize the Ni(I) oxidation state. The complex acts as an active catalyst for the C–C coupling of aryl acetylenes with arylboronic acids containing a variety of substituents. The influence of solvent, base, reaction temperature, and catalyst loading on the C–C coupling reaction was evaluated.

Graphical abstract

A new square-planar nickel(II) complex bearing 2-((3-methylthiophen-2-yl)methylene)-hydrazinecarbothioamide was synthesized and characterized by elemental analysis, FTIR, NMR, and single-crystal X-ray crystallographic technique. Cyclic voltammetric study indicates stabilization of Ni(I) oxidation state. The complex acts as an effective catalyst for the carbon–carbon cross-coupling reaction of substituted phenylacetylenes with various arylboronic acids under optimized conditions.


Datum: 01.10.2017


A one-dimensional Mn(II)-based metal organic oxide: structure and properties

Abstract

A one-dimensional metal organic oxide of Mn(II), with formula [Mn3(OH)2(Hpdc)2]n (H3pdc = 3,5-pyrazoledicarboxylic acid), was prepared via the hydrothermal method and its structure solved by single-crystal X-ray diffraction. The compound exhibits a three-dimensional framework structure, comprising three crystallographically unique Mn atoms bridged by OH ligands (O9 and O10) and O atoms from the Hpdc ligands, forming one-dimensional metal–organic oxide chains. Two kinds of magnetic exchange are observed: a strong antiferromagnetic intra-chain interaction, arising from the short distance between Mn(II) centers, and a ferromagnetic inter-chain interaction, due to the larger distances between the chains. The compound shows good photocatalytic activity for the decomposition of methylene blue in aqueous medium under simulated sunlight.


Datum: 01.10.2017


Transition metal coordination compounds of an antiobesity serotoninergic ligand: spectroscopic characterization and adipogenesis activity

Abstract

Coordination compounds of cobalt(II), nickel(II), copper(II) and zinc(II) with L-5-hydroxytryptophan (L-5-HTP) were synthesized and characterized by elemental analysis, IR and UV–Vis-NIR spectroscopy, mass spectrometry and thermogravimetric analysis. The X-ray structure of the pure enantiomer ligand (L-5-HTP) was obtained. The ligand coordinates to the metal ions in an unidentate mode, where the donor atom is the oxygen from the carboxylic group. The intramolecular H-bond, N1H···O2, observed in the X-ray crystal structure of the free L-5-HTP, remains as a stabilization factor in all of the coordination compounds. Two types of geometries were adopted by the metal centers: tetrahedral and octahedral. In vitro antiadipogenic studies of the coordination compounds showed that the tetrahedral cobalt(II) and copper(II) complexes presented potential antiobesity properties.


Datum: 01.10.2017


Dinuclear copper(II) complexes with ethylenediamine derivative and bridging oxalato ligands: solvatochromism and density functional theory studies

Abstract

Two oxalato-bridged copper(II) complexes of formula, [Cu2(L1)2(µ-ox)](NO3)2·H2O, 1 and [Cu2(L2)2(µ-ox)](NO3)2·H2O, 2 (ox = oxalato dianion, L1 = N,N-dimethyl,N′-benzylethane-1,2-diamine, L2 = N,N-diethyl,N′-benzylethane-1,2-diamine), have been synthesized and characterized by elemental analyses, spectroscopic (IR, UV–Vis) data and molar conductance measurements. The crystal structure of complex 1 was determined by X-ray diffraction analysis, revealing two centrosymmetric dinuclear units. The first consists of a [Cu2(L1)2(µ-ox)(NO3)2] molecule, in which each Cu(II) center is in a square-pyramidal environment, providing two nitrogen atoms from the diamine-chelating ligands plus two oxygen atoms from the oxalate in the basal plane and an oxygen of the nitrate group in the axial position. The second unit [Cu2(L1)2(µ-ox)(H2O)2](NO3)2 has a similar structure, but the apical sites are occupied by water ligands and the nitrate anions are free from coordination. Both complexes are solvatochromic. Their solvatochromism was investigated with different solvent parameter models using SPSS/PC and DFT methodology. The solvatochromic behaviors of the complexes were also explored by TD-DFT in ethanol and acetonitrile solvents. The calculated visible absorption spectra were in accord with the experimental results.


Datum: 01.10.2017


Synthesis, crystal structures, luminescence, and photocatalytic properties of two 1D Co(II) coordination polymers constructed with semirigid bis(benzimidazole) and dicarboxylate ligands

Abstract

Two ternary cobalt(II) coordination polymers (CPs), namely [Co(L1)(npht)] n (1) and {[Co2(L2)2(npht)2(H2O)]·H2O} n (2) (L1 = 4,4′-bis(benzimidazol-1-ylmethyl)biphenyl, L2 = 1,2-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, and H2npht = 4-nitrophthalic acid) have been synthesized and structurally characterized by X-ray crystallography. Both CPs feature similar 1D infinite chains containing two distinct loops. CP 1 further forms a 3D supramolecular network via weak C–H···O hydrogen bond interactions. CP 2 shows a 1D two-layer chain structure, assembled through ππ stacking interactions. The electrochemical, luminescence, and photocatalytic activities of the two CPs for the removal of methylene blue under visible or UV light were investigated. Possible photocatalytic mechanisms are discussed.


Datum: 21.09.2017


Transition metal tetrapentafluorophenyl porphyrin catalyzed hydrogen evolution from acetic acid and water

Abstract

The performance of Cu (1), Co (2) and Zn (3) complexes of meso-tetrakis(pentafluorophenyl)porphyrin in the electrocatalyzed evolution of hydrogen has been investigated. In acetic acid media, hydrogen evolution turnover frequency (TOF) values for complexes 1, 2 and 3 were 22.1, 19.8 and 18.1 h−1, respectively, at an overpotential of 942 mV versus Ag/AgNO3. In buffer solution at pH 7.0, the corresponding hydrogen evolution TOF values increased dramatically, to 266, 234, 218 h−1 at a similar overpotential of 878 mV versus SHE. The Faradaic yields of 1, 2, and 3 for sustained proton reduction in catalytic experiments at a glassy carbon electrode over 72 h were 89.7, 90.4 and 91.0%, respectively, with no observable catalyst decomposition.


Datum: 19.09.2017


Syntheses, crystal structures and magnetic properties of four tetrahydrofuran-2,3,4,5-tetracarboxylato bridged transition metal complexes with N -donor heteroaromatic co-ligands

Abstract

Four tetrahydrofuran-2,3,4,5-tetracarboxylato complexes, Cu(bpy)(H2THFTC) (1), [Cu(phen)(H2THFTC)]·0.5H2O (2), [Mn(phen)(H2THFTC)]·0.5H2O (3) and [Co4(H2O)4(phen)4(THFTC)2]·4H2O (4) (H4THFTC = tetrahydrofuran-2,3,4,5-tetracarboxylic acid, phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine) were synthesized in aqueous solution or under hydrothermal conditions, and characterized. In compounds 13, the metal centers are bridged by tetrahydrofuran-2,3,4,5-tetracarboxylate anions to form 1D chains, which are further assembled into 2D supramolecular layers based on interchain π···π interactions. Compound 4 consists of tetranuclear [Co4(H2O)4(phen)4(THFTC)2] complex molecules and lattice water molecules. The complex molecules are interconnected into hydrogen-bonded chains along the [100] direction, and interdigitation of phen ligands with interchain π···π stacking interactions assembles the hydrogen-bonded chains into 2D supramolecular layers parallel to the (010) plane. Variable-temperature magnetic measurements show an overall weak ferromagnetic behavior for complexes 1 and 2 and antiferromagnetic behavior for complexes 3 and 4.

Graphical Abstract


Datum: 19.09.2017


Synthesis, crystal structures, and luminescent properties of three cluster-based heterometallic and monometallic compounds

Abstract

Two heterometallic cluster compounds and one monometallic cluster compound, namely [Ni9Co6(PMIDA)6(BTC)2(H2O)12]·6H2O (1), [Co13Zn2(PMIDA)6(H2O)18]·6NO3·15H2O (2), and [Fe15(PMIDA)6(BTC)2(H2O)22]·38H2O (3), have been obtained under hydrothermal conditions using N-(phosphonomethyl)imino-diacetic acid (H4PMIDA) and 1,3,5-benzenetricarboxylate acid (H3BTC) as ligands, and structurally characterized by X-ray crystallography. Compound 1 exhibits a 3D open framework constructed from [Ni9Co6(PMIDA)6(H2O)12]6+ heteronuclear clusters and BTC3− ligands. Compounds 2 and 3 are both zero-dimensional polynuclear clusters, further extended into 3D supramolecular structures via hydrogen-bonding interactions. However, there are some differences in their crystal structures; compound 2 features an isolated spherical heteronuclear cation cluster based on PMIDA4− ligands, such that the NO3 anions only balance the charge, whereas compound 3 is characterized as a neutral monometallic cluster incorporating two different types of organic acid ligands, namely PMIDA4− and BTC3−, and the two BTC3− ligands exhibit regular distribution in each cluster. The luminescence properties of all three compounds have been investigated at room temperature.


Datum: 16.09.2017


Substitution of aqua ligands from cis -platinum(II) complexes bearing 2-(phenylthiomethyl)pyridine spectator ligands

Abstract

Cis-Pt(II) complexes, namely [Pt{2-(phenylthiomethyl)pyridine}(H2O)2](CF3SO3)2 Pt(pyS Ph ), [Pt{2-(4-tert-butylphenylthiomethyl)pyridine}(H2O)2](CF3SO3)2 Pt(pyS Ph( t -But) ) and [Pt{2-(4-fluorophenylthiomethyl)pyridine}(H2O)2](CF3SO3)2 Pt(pyS PhF ), were synthesised and characterised. The pK a1 and pK a2 values of the complexes were determined titrimetrically. Substitution of the aqua ligands from these complexes by thiourea nucleophiles was studied at a pH of 2 and ionic strength of 0.1 M under pseudo-first-order conditions using stopped-flow and UV–visible spectrophotometric techniques. Substitution of the aqua ligands depends on both the nature and concentration of the incoming ligand, with low enthalpy and negative entropy of activation values. Substitution of the first and second aqua ligands occurs sequentially and fits the rate laws: k obs (1/2) = k (1/2) [Nu]. The second-order rate constant, k 1, relates to the substitution trans to sulphur, while k 2 is the second-order rate constant for the subsequent substitution of the aqua ligand trans to pyridine. The rate of substitution of the first aqua ligand decreases in the order: Pt(pyS Ph( t -But) ) > Pt(pyS PhF ) > Pt(pyS Ph ), while that of the second decreases in the order: Pt(pyS Ph( t -But) ) > Pt(pyS Ph ) > Pt(pyS PhF ), reflecting the influence of the substituents on the spectator ligands. 195Pt NMR spectra of aged solutions of complexes with the thiourea nucleophile suggest a subsequent but rapid concentration-independent ring opening of the N,S-bidentate ligand to form a PtS 4 species. The crystal structure of Pt(pyS PhF )Cl 2 was elucidated by X-ray diffraction analysis.


Datum: 16.09.2017


Palladacycles incorporating a carboxylate-functionalized phosphine ligand: syntheses, characterization and their catalytic applications toward Suzuki couplings in water

Abstract

A series of acetato-bridged [C^X]-type (C = aryl carbanion, X = N, P) palladacycles (15) of the general formula [Pd(μ-CH3COO)(C^X)]2 were synthesized as metal precursors via slightly modified procedures. However, in the case of complex 5 with Dpbp (Dpbp = 2′-(diphenylphosphino-κP)[1,1′-biphenyl]-2-yl-κC) as the supporting C^P ligand, an unexpected dinuclear complex [Pd(μ-CO2)(Dpbp)]2 (6) was obtained as a by-product and structurally determined by X-ray crystallography. The reactions of complexes 14 with 2-(diphenylphosphino)benzoic acid conveniently afforded four carboxylate-functionalized phosphine complexes [Pd(C^N)(Dpb)] (Dbp = 2-(diphenylphosphino-κP)benzoato-κO, 710), two of which (9/10) are newly synthesized in the present work and have been fully characterized. A comparative catalytic study revealed that complex [Pd(Ppy)(Dpb)] (7) (Ppy = 2-(2-pyridinyl-κN)phenyl-κC) is the best performer in Suzuki cross-couplings in H2O. In addition, complex 7 exhibits much better catalytic activity compared to the non-functionalized phosphine equivalent [Pd(OAc)(PPh3)(Ppy)] (11), which clearly indicates the superiority of incorporating a carboxylate-functionalized phosphine ligand into the palladacycles. A preliminary mechanistic study uncovered a different precatalyst initiation pathway compared to other known analogues of catalyst precursors.


Datum: 15.09.2017


Synthesis and characterization of iminophosphineplatinum(II) complexes of the type (κ 2 - P,N -2-Ph 2 PC 6 H 4 C(H)=NC 6 H 4 X)PtCl 2 (X = OMe, F)

Abstract

A series of iminophosphineplatinum(II) complexes have been prepared from pro-ligands derived from aniline derivatives containing electron-donating methoxy groups or electron-withdrawing fluorides and [PtCl2(η 2 − coe)]2 (coe = cis-cyclooctene). All new pro-ligands and metal complexes have been fully characterized, including an X-ray diffraction study for compound 11 (derived from para-methoxyaniline). Additionally, the molecular structure of a di-iminophosphineplatinum dication 11a has been determined. The platinum compounds showed no appreciable cytotoxic properties against two glioma cell lines using the MTT method.


Datum: 11.09.2017


Electrochemical and photochemical hydrogen generation by a water soluble cobalt(II) complex of 2,2-bipyridine

Abstract

A molecular catalyst based on a cobalt(II) complex, [(bpy)2Co(SCN)(Cl)] 1, has been prepared by the reaction of 2,2-bipyridine (bpy), CoCl2·6H2O, and KSCN. The complex has been investigated for both electrocatalytic hydrogen generation and photocatalytic hydrogen generation from purely aqueous solution. Under photoirradiation with blue light (λ max = 469 nm), with [Ru(bpy)3]Cl2 as a coupled photosensitizer and ascorbic acid (H2A) as a sacrificial electron donor in pH 5.0 aqueous solution, complex 1 possesses good activity with an initial turnover rate of 2.7 × 103 mol of H2 per mole of catalyst for the first 3 h of photolysis. This activity can be sustained for at least 10 h with a turnover number of 1.2 × 104 mol of H2 per mole of catalyst. Additionally, complex 1 electrocatalyzes hydrogen generation from neutral water (pH 7.0) with a turnover frequency of 809 mol of hydrogen per mole of catalyst per hour at an overpotential of 837.6 mV.


Datum: 08.09.2017


Base hydrolysis of tris(3-(2-pyridyl)-5,6-bis(4-phenyl sulphonic acid)-1,2,4-triazine)iron(II) in aqueous, SDS and CTAB media: kinetic and mechanistic study

Abstract

The kinetics and mechanism of base hydrolysis of tris(3-(2-pyridyl)-5,6-bis(4-phenyl sulphonic acid)-1,2,4-triazine)iron(II), \({\text{Fe}}({\text{PDTS}})_{3}^{4 - }\) have been studied in aqueous, sodium dodecyl sulphate (SDS) and cetyltrimethyl ammonium bromide (CTAB) media at 25, 35 and 45 °C under pseudo-first-order conditions, i.e. \(\left[ {\text{OH}^{ - } } \right]\)  ≫  \({\text{Fe}}({\text{PDTS}})_{3}^{4 - }\) . The reaction is first order each in \({\text{Fe}}({\text{PDTS}})_{3}^{4 - }\) and hydroxide ion. The rate increases with increasing ionic strength in aqueous and SDS media, whereas this parameter has little effect in CTAB. In SDS medium, the rate-determining step involves the reaction between \(\left[ {\text{OH}^{ - } } \right]\) and \({\text{Fe}}({\text{PDTS}})_{3}^{4 - }\) , whereas in CTAB medium, it involves reaction between a neutral ion pair, { \({\text{Fe}}({\text{PDTS}})_{3}^{4 - }\) ·4CTA+} and \(\left[ {\text{OH}^{ - } } \right]\) ions. The specific rate constants and thermodynamic parameters (E a, ΔH #, ΔS # and ΔG 35°C # ) have been evaluated in all three media. The near equal values of ΔG 35°C # obtained in aqueous and SDS media suggest that these reactions occur essentially by the same mechanism. Slightly lower ΔG 35°C # values in CTAB medium can be attributed to a higher concentration of reactants in the Stern layer. The reaction is inhibited in SDS medium but catalysed in CTAB. The former can be attributed to the anionic surfactant creating more repellent space between the reactants. Catalysis in CTAB medium is ascribed to electrophilic and hydrophilic interactions between hydroxide ion/substrate with the cationic Stern layer, resulting in increased local concentrations of both reactants.


Datum: 08.09.2017


Organophosphine ligands in PtPX 2 Y and PtPXYZ complexes; structural aspects

Abstract

This review covers over ninety platinum complexes with PtPX2Y and PtPXYZ inner coordination spheres, in which the P-donor ligands are organomonophosphines. These complexes crystallize in four crystal systems: tetragonal (×3), orthorhombic (×17), triclinic (×20) and monoclinic (×56). Complexes with the PtPX2Y chromophore exist in cis- as well as trans-configurations; however, the latter prevails. There are four types of ligands which create such chromophores: monodentate (H, OL, NL, CO, BL, Cl, SL, Br, SeL and I); homobidentate (O2L, N2L, S2L, Se2L and As2L); heterobidentate (O/N, O/S, N/S, N/Se and N/Te); and heterotridentate (O/O/N, N/N/S, N/N/Se, O/S/S, Se/N/Se and O/N/S). The chelating ligands create four-, five- and six-membered metallocycles, and the effects of both steric and electronic factors can be seen from the values of the L–Pt–L bite angles. The structural parameters are analyzed and discussed, with particular attention to trans-effects. Three types of isomerism are identified, namely cistrans, distortion and ligands.


Datum: 01.09.2017






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