Synthesis and photoactivity of novel cationic photoinitiators: (η-Diphenylmethane) (η-cyclopentadienyl) iron hexafluorophosphate and (η-benzophenone) (η-cyclopentadienyl) iron hexafluorophosphate

Two novel cationic photoinitiators (η⁶-diphenylmethane) (η⁵-cyclopentadienyl) iron hexafluorophosphate (PhCH₂PhFe⁺CpPF₆⁻) and (η⁶-benzophenone) (η⁵-cyclopentadienyl) iron hexafluorophosphate (PhCOPhFe⁺CpPF₆⁻), were synthesized, characterized, and studied. PhCH₂PhFe⁺CpPF₆⁻ was prepared by straightforward synthetic techniques with ferrocene and diphenylmethane and PhCOPhFe⁺CpPF₆⁻ was synthesized from oxidation of diphenylmethane–cyclopentadienyliron salt. Their activity as cationic photoinitiators was studied using real-time infrared spectroscopy. The results obtained showed that PhCH₂PhFe⁺CpPF₆⁻ and PhCOPhFe⁺CpPF₆⁻ are capable of photoinitiating the cationic polymerization of epoxy monomer directly on irradiation with long-wavelength UV light. Comparative studies also demonstrated that PhCH₂PhFe⁺CpPF₆⁻ exhibited better efficiency than I-261 and PhCOPhFe⁺CpPF₆⁻. DSC studies showed that PhCOPhFe⁺CpPF₆⁻ and PhCH₂PhFe⁺CpPF₆⁻ photoinitiators in epoxides possess good thermal stability in the absence of light.     

Visible light curing of bisphenol-A epoxides and acrylates photoinitiated by (η6-benzophenone)(η5-cyclopentadienyl) iron hexafluorophosphate

Visible light curing of diglycidyl ether of bisphenol-A (DGEBA) epoxy oligomer and acrylate monomers photoinitiated by (η⁶-benzophenone)(η⁵-cyclopentadienyl) iron hexafluorophosphate (Fc-BP) under a halogen lamp were studied by near infrared spectroscopy. Fc-BP exhibited high efficiency in the radical photopolymerization of acrylate monomers, even without the presence of tertiary amines. Under the same light source, however, benzophenone did not show any photoinitiating ability. Fc-BP could also be used to photoinitiate the cationic polymerization of DGEBA. There was an obvious increase in the photopolymerization rate of DGEBA and a decrease in the induction period when benzoyl peroxide was used as a photosensitizer. The induction period at the beginning of DGEBA cationic polymerization was eliminated by introducing a certain amount of cycloaliphatic epoxy monomer ERL4221 as an active diluent. However, the final epoxy conversion was decreased when ERL4221 was used.     

Synthesis of UHMW-PE by a Highly Active Homogeneous System: η5-(C5H5)2Ti(η1-OC(O)C6H5)2/MAO

Summary The complex ⁵-(C₅H₅)₂Ti (¹-OC(O)C₆H₅)₂ was synthesized and activated with MA0 for ethylene polymerization. The resultant polymer is UHMW-PE with a viscosimetric molecular weight of Mv = 6.8 x 10⁶ to 0.7 x 10⁶ g/mol dependent on the temperature of the reaction. The effects of the Al/Ti molar ratio and temperature of the reaction on the catalytic activity and polymer properties were studied.     

Zirconocene complexes of the sterically demanding pentaphenylcyclopentadienyl ligand,CpPRO. Synthesis and characterization of CpPROZrCl3 and CpCpPROZrCl2 (Cp=η5-C5H5; CpPRO=η5-C5(C6H5)5)

The synthesis, characterization and X-ray structures of two zirconium complexes of the bulky pentaphenylcyclopentadienyl ligand, Cp^PRO, are reported. The monocyclopentadienyl 12 electron complex, Cp^PROZrCl₃ (I), has an unusual monomeric structure in the solid state and has short Zr–ligand distances. The Lewis acidity of this complex is manifested in its ability to catalyze the [4+2] cycloadditions of methyl- and ethylmethacrylate to cyclopentadiene. The sandwich complex, Cp^PROCpZrCl₂ (II), has more typical Zr–ligand distances, but has a more parallel arrangement of the two cyclopentadienyl rings.     

Synthesis and structure of the cubane type [Fe2Sb(CO)5(η5-C5H5)]4 cluster

The [Fe₂Sb(CO)₅Cp]₄ (Cp=η⁵-C₅H₅) cluster has been obtained by the thermolysis of [Et₄N][{Fe(CO)₄}₂{Fe(CO)₂Cp}SbI]. The structure of the [Fe₂Sb(CO)₅Cp]₄·2toluene solvate has been determined by X-ray analysis. The cluster contains the cubane [Fe₄Sb₄] core. Each Sb serves as a μ₄-ligand between three iron atoms of the core and one of a terminal [Fe(CO)₂Cp] group.     

Electrochemical anion recognition by redox-responsive unnatural amino acid derivatives; the X-ray crystal structure of N-ferrocenoyl glycine methyl ester, (η5-C5H5)Fe(η5-C5H4)CONHCH2COOMe

N-Ferrocenoyl glycine ester derivatives FcCONHCH₂COOR (Fc=(η⁵-C₅H₅)Fe(η⁵-C₅H₄); R=methyl (1), ethyl (2) and benzyl (3)) have been prepared by coupling ferrocene carboxylic acid to a series of glycine esters using 1,3-dicyclohexylcarbodiimide (DCC), 1-hydroxybenzotriazole (HOBT) and Et₃N in CH₂Cl₂. The electrochemical anion sensing using a platinum microdisk working electrode of these N-ferrocenoyl glycine ester derivatives is reported. The crystal structure of 1 has been determined; principal dimensions are amide N(H)CO 1.229(3) Å, ester CO 1.183(3) Å with N–H⋯OC(amide) as the primary intermolecular hydrogen bond, N⋯O 2.804(3) Å.     

A novel route to titanium compounds containing cyclopentadienyl ligands with bromoethyl substituents; molecular structure of [(η5-C5H4CH2CH2Br)TiBr(μ-O)]4

Compounds (η⁵-C₅H₄CH₂CH₂OCH₃)TiCl₃, (η⁵-C₅H₄CH₂CH₂OCH₃)₂TiCl₂ and (η⁵-C₅H₄CH₂CH₂OCH₃)(η⁵-C₅H₅)TiCl₂ react with BBr₃ to give a high yield of titanium compounds containing cyclopentadienyl ligands with bromoethyl substituents, (η⁵-C₅H₄CH₂CH₂Br)TiBr₃ (1), (η⁵-C₅H₄CH₂CH₂Br)₂TiBr₂ (3) and (η⁵-C₅H₄CH₂CH₂Br)(η⁵-C₅H₅)TiBr₂ (4), respectively. Hydrolysis of 1 in the presence of tert-butylamine affords cyclo-[(η⁵-C₅H₄CH₂CH₂Br)TiBr(μ-O)]₄ (2) in quantitative yield. The molecular structure of 2 was determined by X-ray diffraction.     

The synthesis and characterization of two new 19-vertex metallaborane clusters: [B18H20Ni(η5-C5H5)]−1 and [B18H19(2-THF)Ni(η5-C5H5)]

Two new 19-vertex metallaboranes, [B₁₈H₂₀Ni(η⁵-C₅H₅)][N(CH₃)₄] and [B₁₈H₁₉(2-THF)Ni(η⁵-C₅H₅)], were isolated from the reaction of anti-B₁₈H₂₂ with nickelocene, [Ni(η⁵-C₅H₅)₂], in high yields. The complexes were characterized by multinuclear NMR (¹H, ¹³C, ¹¹B), IR and UV–vis spectroscopy. Single-crystal X-ray diffraction analyses of these new complexes confirmed their structures as 19-vertex conjuncto-metallaborane clusters.     

A convenient method for the synthesis of [Pd{[(η5-C5H3)–CHN–(CH2)2–NMe2]Fe(η5-C5H5)}Cl] and the study of its reactivity with diphosphines

A one-pot method for the preparation of [Pd{[(η⁵-C₅H₃)–CHN–(CH₂)₂–NMe₂]Fe(η⁵-C₅H₅)}Cl] is described. Its X-ray crystal structure and its reactions with the diphosphines Ph₂P–(CH₂)_n–PPh₂ {with n=1 (ddpm) or 2 (dppe)} are also reported.     

Synthesis of novel organometallic polymers having metallacyclopentadiene moieties in the main chain by the reaction of diynes with (η5-cyclopetadienyl)bis(tripheylophospihne)cobalt complex

Summary Polymerization reactions of ⁵-cyclopentadienyl)bis(triphenylphosphine)cobalt complex (2) and diyne monomers (3a-3c) were examined to obtain novel organometallic polymers bearing metallacyclopentadiene moieties in the main chain. When the polymerization reaction of 2 with 4,4-bis(phenylethynyl)biphenyl (3a) was carried out in toluene at 50°C for 3days, an organometallic polymer having cobaltacyclopentadiene in the main chain was obtained quantitatively. The structure of the resulting polymer was confirmed by ¹H-, ¹³C-NMR, IR, and UV spectra. The number-average molecular weight of the obtained polymer was evaluated as 9,600 (GPC, on the basis of polystyrene).     

Theoretical study of the reactive intermediate Si2Me4[(η5-C5H4) Fe(CO)2] 2 2−

In two previous papers (Kinget al., J. Organomet. Chem. 19, 327, 1969; Pannellet al., Organometallics 9, 859, 1990), the synthesis and X-ray structure of the two tetramethyl disilyl complexes [(η⁵-C₅H₅) Fe(CO)₂]₂Si₂Me₄ (I) and Si₂Me₄[(η⁵-C₅H₄) Fe(CO)₂CH₃]₂ (II) were reported. ComplexII is obtained fromI [2]. However, attempts to form other derivatives fromI have generally failed. In the chemical process to getII fromI, an intermediate complex, Si₂Me₄[(η⁵-C₅H₄) Fe(CO)₂] ₂ ^2? (III), is probably formed. This is similar to complexII without the two methyl groups bonded to the Fe atoms. Therefore, a theoretical study that may shed some light on the intermediate structure, stability, and reactivity is justified. We have developed theoretical studies consisting of extended Huckel electronic structure calculations on the simulated intermediate geometry. The results obtained from these calculations suggest that it might be stable enough to form during reactions of complexI. The more reactive sites, which suggest reaction alternatives, are pointed out.     

Characterization of rigid endo- and exo-η3-allyl carbonyl diethyldithiophosphate molybdenum complexes: crystal structure of endo-Mo(η3-allyl)(CO){η2-S2P(OEt)2}(Dppe)

The stereochemical rigid complexes endo-Mo(η³-allyl)(CO){η²-S₂P(OEt)₂}(η²-dppm) (2a) and exo-Mo(η³-allyl)(CO){η²-S₂P(OEt)₂}(η²-dppm) (2b) are accessible by the reaction of complex Mo(η³-allyl)(CO)₂{η²-S₂P(OEt)₂}(CH₃CN) (1) with dppm in refluxing acetonitrile. Treatment of 1 with dppe in the similar reactive conditions of 2 affords the sole complex endo-Mo(η³-allyl)(CO){η²-S₂P(OEt)₂}(η²-dppe) (3). Complex 3 is characterized by X-ray diffraction analysis.     

Three-liquid-phase extraction and separation of V(V) and Cr(VI) from acidic leach solutions of high-chromium vanadium–titanium magnetite

A new method by liquid–liquid–liquid three phase system, consisting of acidified primary amine N1923(abbreviated as A-N1923), poly(ethylene glycol)(PEG) and (NH_4)_2SO_4 aqueous solution, was suggested for the separation and simultaneous extraction of V(V) and Cr(VI) from the acidic leach solutions of highchromium vanadium–titanium magnetite. Experimental results indicated that V(V) and Cr(VI) could be selectively enriched into the A-N1923 organic top phase and PEG-rich middle phase, respectively, while Al(III)and other co-existing impurity ions, such as Si(IV), Fe(III), Ti(IV), Mg(II) and Ca(II) in acidic leach solutions,could be enriched in the(NH_4)_2SO_4 bottom aqueous phase. During the process for extraction and separation of V(V) and Cr(VI), almost all of impurity ions could be removed. The separation factors between V(V) and Cr(VI) could reach 630 and 908, respectively in the organic top phase and PEG middle phase, and yields of recovered V(V) and Cr(VI) in the top phase and middle phase respectively were all above 90%.Various effects including aqueous p H, A-N1923 concentration, PEG added amount and(NH_4)_2SO_4 concentration on three-phase partitioning of V(V) and Cr(VI) were discussed. It was found that the partition of Cr(VI) into the PEG-rich middle phase was driven by hydrophobic interaction, while extraction of V(V) by A-N1923 resulted of anion exchange between NO_3~- and H_2V_(10)O_(28)~(-4). Stripping of V(V) and Cr(VI) from the top organic phase and the middle PEG-rich phase were achieved by mixing respectively with NaNO_3 aqueous solutions and Na OH-((NH_4)_2SO_4 solutions. The present work highlights a new approach for the extraction and purification of V and Cr from the complex multi-metal co-existing acidic leach solutions of high-chromium vanadium–titanium magnetite.     

Reductive dimerization of α-bromoimines via (η3-1-azaallyl)dicarbonylnitrosyliron complexes

Reaction of two equivalents of α-bromo-N-methoxyalkanimines with tetra-n-butylammonium tricarbonylnitrosylferrate gave a reductively dimerized product of α-bromoimines, in which the reaction (η³-1-azaallyl)dicarbonylnitrosyliron complexes are intermediates for the dimerization reaction of α-bromoimines. Variable temperature ¹H NMR study of the η³-1-azaallyl iron complex thus obtained demonstrated that the bonding of the azaallyl ligand is fluxional at room temperature, but is fixed below 233 K.     

Effect of nano-titania (η-TiO2) content on the mechano-physical properties of a magnesia refractory composite

The mechano-physical properties of a sintered magnesia matrix containing 0–8 wt% nano-titania (η-TiO₂) have been investigated. The crystalline phases and microstructure characteristics of the refractory specimens sintered by solid state at 1500 °C for 4 h in an electric furnace were studied by X-ray diffraction (XRD), and scanning electron microscopy (SEM) with microanalysis (EDS), respectively. The physical properties are reported in terms of density and porosity. The mechanical behavior was evaluated by a cold crushing strength (CCS) test. As a result, it was found that the presence of η-TiO₂ in the magnesia matrix induced titanates formation (Mg₂TiO₄ and CaTiO₃), which improved the sintering process. Nano-titania also produced a fine-grained microstructure with intergranular second phase particles, which remain at the boundary and exert a pinning effect. In general, the addition of 5 wt% of η-TiO₂ contributed to reach a maximum increment in physical and mechanical properties.     

Dynamic IR properties of Fe(CO)3(η4-2,5-norbornadiene) and its radical anion

A variable temperature specular reflectance cell for thin layer spectroelectrochemistry (SEC) in the infrared and UV–Vis regions was employed to study the reduction of neutral Fe(CO)₃(η⁴-NBD) (1) (NBD=2,5-norbornadiene) to its radical-anion Fe(CO)₃(η⁴-NBD) (1⁻). Together 1 and 1⁻ comprise an unusual case where a dynamic contribution to IR spectral features can be observed in one redox state (1), but not the other (1⁻).     

Effect of poly(ε-caprolactone) and titanium (IV) dioxide content on the UV and hydrolytic degradation of poly(lactic acid)/poly(ε-caprolactone) blends

The effect of accelerated weathering degradation on the properties of poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blends and PLA/PCL/titanium (IV) dioxide (TiO₂) nanocomposites are presented in this paper. The results show that both polymers are susceptible to weathering degradation, but their degradation rates are different and are also influenced by the presence of TiO₂ in the samples. Visual, microscopic and atomic force microsocpy observations of the surface after accelerated weathering tests confirmed that degradation occurred faster in the PLA/PCL blends than in the PLA/PCL/TiO₂ nanocomposites. The X-ray diffraction results showed the degradation of PCL in the disappearance of its characteristic peaks over weathering time, and also confirmed that PLA lost its amorphous character and developed crystals from the shorter chains formed as a result of degradative chain scission. It was further observed that the presence of TiO₂ retarded the degradation of both PLA and PCL. These results were supported by the differential scanning calorimetry results. The thermogravimetric analysis results confirmed that that PLA and PCL respectively influenced each other's thermal degradation, and that TiO₂ played a role in the thermal degradation of both PLA and PCL. The tensile properties of both PLA/PCL and PLA/PCL/TiO₂ were significantly reduced through weathering exposure and the incorporation of TiO₂.