General aspects of ethylene polymerization by d0 and d0f n transition metals

We present a generalized view of d⁰and d⁰f ⁿ metal complexes as olefin polymerization catalysts from computational studies of the {L}M–C₂H₅ ^(0,+,2+)-fragments (M = Sc(III), Y(III), La(III), Lu(III), Ti(IV), Zr(IV), Hf(IV), Ce(IV), Th(IV) and V(V); L = NH–(CH)₂–NH^2- {1}, N(BH₂)–(CH)₂–(BH₂)N^2- {2}, O–(CH)₃–O^- {3}, Cp₂ ^2- {4}, NH–Si(H₂)–C₅H₄ ^2- {5}, {(oxo)(O–(CH)₃–O)}^3- {6}, (NH₂)₂ ^2- {7}, (OH)₂ ^2- {8}, (CH₃)₂ ^2- {9}, NH–(CH₂)₃–NH^2- {10} and O–(CH₂)₃–O^2- {11}). This revised version was published online in June 2006 with corrections to the Cover Date.     

Metallkomplexe mit biologisch wichtigen Liganden. CXXIII. Darstellung von Isophthaloyl‐ und Terephthaloyl‐di‐[(β,γ,δ)‐amino‐α‐aminocarboxylat]‐verbrückten zweikernigen Ruthenium‐, Rhodium‐ und Iridium‐Halbsandwich‐Komplexen

The reaction of the Cu(II) bis N,O‐chelate‐complexes of L‐2,4‐diaminobutyric acid, L‐ornithine and L‐lysine {Cu[H₂N–CH(COO)(CH₂)_nNH₃]₂}²⁺(Cl^–)₂ (n = 2–4) with terephthaloyl dichloride or isophthaloyl dichloride gives the polymeric complexes {‐OC–C₆H₄–CO–NH–(CH₂)_n–CH(nh₂)(COO)Cu(OOC)(NH₂)CH–CH₂)_n–NH‐}_x 1 – 5 . From these the metal can be removed by precipitation of Cu(II) with H₂S. The liberated ω,ω′‐N,N′‐diterephthaloyl (or iso‐phthaloyl)‐diaminoacids 6 – 10 react with [Ru(cymene)Cl₂]₂, [Ru(C₆Me₆)Cl₂]₂, [Cp*RhCl₂]₂ or [Cp*IrCl₂]₂ to the ligand bridged bis‐amino acidate complexes [L_n(Cl)M–(OOC)(NH₂)CH–(CH₂)_nNH–CO]₂–C₆H₄ 11 – 14 .     

Highly Active Catalyst from [PdCl2(NH2(CH2)12CH3)2] on NH4ZSM-5

A palladium catalyst highly active for the cyclohexene hydrogenation has been obtained by heterogenisation of [PdCl₂(NH₂(CH₂)₁₂CH₃)₂] on zeolite NH₄ZSM-5. TOF is more than twenty times higher than for the homogeneous catalyst or the activated carbon heterogenised complex. Changes in the electronic state of palladium have been observed by XPS analysis. Palladium reduction is produced upon heterogenisation on the NH₄ZSM-5 zeolite.     

A Facile Access to New Polymethylmethacrylate-Anchored Ferrocene Substituted Nickel(II) Unsymmetrical Schiff Base Complexes: Synthesis and Characterization

This paper discloses two new side-chain metallopolymers containing an unsymmetrical organometallic Schiff base complex of Ni(II) linked to a polymethylmethacrylate (PMMA) matrix. The neutral ferrocene substituted Schiff base complex 1, Ni{CpFe(η⁵-C₅H₄)-C(O)CH=C(CH₃)N–o-C₆H₄N=CH-(2-O,5-OH-C₆H₃)} where (Cp = η⁵-C₅H₅), was synthesized via template reaction by condensation of the tridentate half-unit metalloligand Fc-C(O)CH=C(CH₃)-N(H)-o-C₆H₄NH₂ (Fc = ferrocenyl = CpFe(η⁵-C₅H₄)) with 2,5-dihydroxybenzaldehyde in the presence of nickel(II) acetate tetrahydrate. The binuclear Schiff base complex of Ni(II) containing an aromatic free hydroxyl group was reacted under basic conditions with PMMA to afford, upon trans-esterification reaction, metallopolymers 2 (complex 1 monomeric unit/PMMA = 1/5) and 3 (complex 1 monomeric unit/PMMA = 1/3). Elemental analysis, FT-IR, ¹H and ¹³C NMR spectroscopies, and cyclic voltammetry were utilized to characterize the newly synthetized compounds. Surface morphology of the metallopolymer film of 2 was studied using atomic force microscopy.     

The Effect of CO2 and H2O on the Kinetics of NO Reduction by CH4 Over Sr-Promoted La2O3

The influence of CO₂ and H₂O on the activity of 4% Sr-La₂O₃ mimics that observed with pure La₂O₃, and a reversible inhibition of the rate is observed. CO₂ causes a greater effect, with decreases in rate of about 65% with O₂ present and 90% in its absence, while with H₂O in the feed, the rate decreased around 35-40% with O₂ present or absent. The influence of these two reaction products on kinetic behavior can be described by assuming competitive adsorption on the surface, incorporating adsorbed CO₂ and H₂O in the site balance, and using rate expressions previously proposed for this reaction over Sr-promoted La₂O₃. In the absence of O₂, the rate expression is $$r_{N_2 } = \frac{{k'P_{{\text{NO}}} P_{{\text{CH}}_{\text{4}} } }}{{{\text{(1 + }}K_{{\text{NO}}} P_{{\text{NO}}} {\text{ + }}K_{{\text{CH}}_{\text{4}} } P_{{\text{CH}}_{\text{4}} } {\text{ + }}K_{{\text{CO}}_{\text{2}} } P_{{\text{CO}}_{\text{2}} } {\text{ + }}K_{{\text{H}}_{\text{2}} {\text{O}}} P_{{\text{H}}_{\text{2}} {\text{O}}} {\text{)}}^{\text{2}} }},$$ which yields a good fit to the experimental data and gives optimized equilibrium adsorption constants that demonstrate thermodynamic consistency. With O₂ in the feed, nondifferential changes in reactant concentrations through the reactor bed were accounted for by assuming integral reactor behavior and simultaneously considering both CH₄ combustion and CH₄ reduction of NO, which provided the following rate law for total CH₄ disappearance: $$(r_{{\text{CH}}_{\text{4}} } )_{\text{T}} = \frac{{k'_{{\text{com}}} P_{{\text{CH}}_{\text{4}} } P_{{\text{O}}_{\text{2}} }^{{\text{0}}{\text{.5}}} + k'_{{\text{NO}}} P_{{\text{NO}}} P_{{\text{CH}}_{\text{4}} } P_{{\text{O}}_{\text{2}} }^{{\text{0}}{\text{.5}}} }}{{{\text{(1 + }}K_{{\text{NO}}} P_{{\text{NO}}} {\text{ + }}K_{{\text{CH}}_{\text{4}} } P_{{\text{CH}}_{\text{4}} } {\text{ + }}K_{{\text{O}}_{\text{2}} }^{{\text{0}}{\text{.5}}} P_{{\text{O}}_{\text{2}} }^{{\text{0}}{\text{.5}}} {\text{ + }}K_{{\text{CO}}_{\text{2}} } P_{{\text{CO}}_{\text{2}} } {\text{ + }}K_{{\text{H}}_{\text{2}} {\text{O}}} P_{{\text{H}}_{\text{2}} {\text{O}}} {\text{)}}^{\text{2}} }}.$$ The second term of this expression represents N₂ formation, and it again fit the experimental data well. The fitting constants in the denominator, which correspond to equilibrium adsorption constants, were not only thermodynamically consistent but also provided entropies and enthalpies of adsorption that were similar to values obtained with other La₂O₃-based catalysts. Apparent activation energies typically ranged from 23 to 28 kcal/mol with O₂ absent and 31-36 kcal/mol with O₂ in the feed. With CO₂ in the feed, but no O₂, the activation energy for the formation of a methyl group via interaction of CH₄ with adsorbed NO was determined to be 35 kcal/mol.     

First ditelluride containing Schiff base functionality: Synthesis and instantaneous ligand exchange with other ditelluride investigated by 125Te NMR

The first ditelluride having Schiff base functionality (2-HOC₆H₄(CH₃)C NCH₂CH₂Te)₂ (4) has been synthesized by reacting H₂NCH₂CH₂TeTeCH₂CH₂NH₂ with 2-hydroxyacetophenone under anaerobic conditions. Compound 4 gives in ¹²⁵Te{¹H} NMR spectrum signal at 98.0 ppm, which is characteristic of a ditelluride. The ¹²⁵Te{¹H} NMR spectral studies on the mixture of 4 and (4-CH₃OC₆H₄Te)₂ indicate the instantaneous formation of 2 HOC₆H₄(CH₃)CNCH₂CH₂Te–TeC₆H₄-4-OCH₃ (6) in equilibrium with the precursor ditellurides. This ligand exchange equilibrium is attained instantaneously. It is supported by ¹³C{¹H} NMR spectra also.     

Copper Complexes Obtained from the Schiff Base of Quinoline-2-Aldehyde and Aliphatic Diamines

Schiff base bis (2— quinolidene)- diamine gives a purple-red complex with copper ions with a λ_max at 530 mμ. The optimum pH for production of this complex is approximately 9.5. None of the metallic ions of the analytical groups II and III give rise to red complexes with the above Schiff base. Manganous (Mn²⁺) and stannous (Sn²⁺)ions as well as reducing agents such as hydrazine or hydroxylamine exert a catalytic effect on the rate of formation of these copper complexes. The thermal stability of the copper complex formed from the Schiff bases (2-quinoline-aldehyde with NH₂-(CH₂)_n-NH₂) is greater for diamine for which n = 4–6 than for n = 2–3.     

Syntheses and characterization of a chelating resin containing ONNO donor quadridentate Schiff base and its coordination complexes with copper(II), nickel(II), cobalt(II), iron(III), zinc(II), cadmium(II), molybdenum(VI) and uranium(VI),

A new mixed Schiff base N,N′-ethylenemono(3-carboxysalicylideneimine)mono(salicylideneimine) has been synthesized by the condensation of equimolar quantities of ethylenediamine, salicylaldehyde and 3-formylsalicylic acid. A polymer supported Schiff base (PS–CH₂–LH₂) has been synthesized by the reaction of chloromethylated polystyrene (containing 3.9 mmol of chlorine per g of resin and 2% cross-linked with divinylbenzene) and the Schiff base N,N′-ethylenemono(3-carboxysalicylideneimine)mono(salicylideneimine). The polymer-anchored Schiff base reacts with metal salt/metal complex and forms polymer-anchored complexes having the formulae PS–CH₂–LCu, PS–CH₂–LNi, PS–CH₂–LCo, PS–CH₂–LFeCl·DMF, PS–CH₂–LZn, PS–CH₂–LCd, PS–CH₂–LMoO₂ and PS–CH₂–LUO₂. The polymer-anchored complexes have been characterized on the basis of elemental analysis, infrared and electronic spectra and magnetic susceptibility measurements. The shifts of the ν(CN) (azomethine) stretch to lower energy and ν(CO) (carboxylic) to higher energy in the polymer-anchored complexes indicate the ONNO donor behaviour of the chelating resin. The metal ions in the metal bound polymers can be leached by hot dilute formic acid, acetic acid or hydrochloric acid. The coordinated dimethylformamide is completely lost on heating the complexes in air. The complexes PS–CH₂–LCu and PS–CH₂–LCo are paramagnetic with square planar structure, PS–CH₂–LNi is diamagnetic with square planar structure and PS–CH₂–LFeCl·DMF is paramagnetic and octahedral, PS–CH₂–LZn and PS–CH₂–LCd are diamagnetic and tetrahedral, PS–CH₂–LMoO₂ and PS–CH₂–LUO₂ are diamagnetic and have octahedral structure. The stoichiometry and the structure of the metal bound polymers are comparable with those of metal complexes of N,N′-ethylenebis(salicylideneimine). This is the first report of the syntheses of a mixed Schiff base and its coordination complexes.     

Activated-Carbon-Heterogenized [PdCl2(NH2(CH2)12CH3)2] for the Selective Hydrogenation of 1-Heptyne

The complex [PdCl₂(NH₂(CH₂)₁₂CH₃)₂] has been heterogenized on two different activated carbons and tested as a catalyst for the semihydrogenation of 1-heptyne. The results are compared with those previously reported with the -Al₂O₃-supported complex. An important effect of the support porosity has been found. The location of the complex in the narrow pores induces shape selectivity. The effect of the support in concentrating the substrate close to the active species has been observed. A very active and selective catalyst has been prepared using an essentially microporous carbon.     

Synthesis of NaTi2(PO4)3 by the Inorganic–Organic Steric Entrapment Method and Its Thermal Expansion Behavior

Crystalline pure NaTi₂(PO₄)₃ (NTP) powder was synthesized at 700°C using a simple and low energy, hybrid inorganic–organic, steric entrapment method. Sodium nitrite (NaNO₂) and ammonium phosphate dibasic ((NH₄)₂HPO₄) dissolved in water, whereas titanium (IV) isopropoxide (Ti[OCH(CH₃)₂]₄) hydrolyzed in water. Ethylene glycol (HOCH₂CH₂OH) was used as a polymeric entrapper and hydrolysis of the Ti source was hindered by its dissolution in isopropyl alcohol. The resulting NTP powder was characterized by thermogravimetric analysis/differential thermal analysis, X‐ray diffractometry, scanning electron microscopy, specific surface area by Brunauer–Emmett–Teller nitrogen absorption, and particle size analysis. Furthermore, C, H, N were measured by the classical Pregl‐Dumas method. The thermal expansion behavior in all {hkl} pole directions was also determined by in situ high‐temperature X‐ray diffraction using synchrotron radiation and was found to be in agreement with other published studies.     

A tetranuclear oxofluorovanadium(IV) cluster encapsulating a Na(H2O)n+ subunit

Hydrothermal reactions of sodium vanadate, methylenediphosphonic acid, hydrogen fluoride and the appropriate organoamine yielded the vanadium(IV)-oxyfluoride compounds [NH₃(CH₂)₂(NH₂)(CH₂)₂NH₃]₃[{Na(H₂O)} ⊂ {V₄O₄F₂(O₃PCH₂PO₃)₄}]·8H₂O (1·8H₂O) and [NH₃(CH₂)₂(NH₂)(CH₂)₂(NH₂)(CH₂)NH₃]₂[{Na(H₂O)} ⊂ {V₄HO₄F₂(O₃PCH₂PO₃)₄}]·7H₂O (2·7H₂O). The vanadium-oxyfluoride cationic unit {V₄O₄F₂(O₃PCH₂PO₃)₄}^10 − of the compounds consists of pairs of fluoride bridged {VFO₅} octahedra linked through η⁴-diphosphonate ligands into a three polyhedra thick band. The {Na(H₂O)_n}⁺ groups occupy the interior of the band but are displaced from the centroid toward one face so as to project the aqua ligands into the extra-annular domain. The fluoride ligands bridge two vanadium sites as well as coordinating to the sodium cation.     

Characterization and Evaluation of Methylcyclopentane and Cyclohexane Ring Opening over Ir/ZrO2–MoO3 Catalysts

Methyl bromide was synthesized by reacting methane with oxygen and hydrogen bromide over Rh/SiO₂ catalyst. The reaction started from the oxidation of HBr to form active bromine species (Br^? radicals and Br* surface species), which in turn reacted with CH₄ to form CH ₃ ^? radicals and $\hbox{CH}_{3}^{\ast}$ surface species. These CH ₃ ^? and $\hbox{CH}_{3}^{\ast}$ species reacted with the active bromine species to form CH₃Br and CH₂Br₂. The presence of HBr inhibited the deep oxidation and the steam reformation of CH₄ and therefore, guaranteed the high selectivity of CH₃Br. In the presence of HBr, CO was formed from the oxidation and steam reformation of CH₃Br, while CO₂ was formed from the oxidation and steam reformation of CO over Rh/SiO₂ at reaction temperature higher than 560 °C.     

Preparation of Photodegradable Oligomers Containing Metal–Metal Bonds Using ADMET

ADMET was evaluated as a method for preparing organometallic polymers with metal–metal bonds in the main chain. The Cp₂Mo₂CO₄(Ph₂P(CH₂)₆CH=CH₂)₂ complex was synthesized, and the X-ray crystal structure is reported. The molecule did not undergo ADMET polymerization with Grubbs’ or Schrock’s catalysts. In a control experiment to test if the Ph₂P(CH₂)₆CH=CH₂ ligand was interfering with the ADMET reaction, the phosphine was reacted with Grubbs’ 2nd generation catalyst. The dimerized metathesis product Ph₂P(CH₂)₆CH=CH(CH₂)₆PPh₂ was obtained with no observed degradation or deactivation of the catalyst. To test the inherent ADMET reactivity of the Ph₂P(CH₂)₆CH=CH₂ ligand when it is bonded to a metal center, the mononuclear cis-Mo(CO)₄(Ph₂P(CH₂)₆CH=CH₂)₂ complex was synthesized and polymerized using Grubbs’ 2nd generation catalyst. These control experiments suggest that the inability of Cp₂Mo₂CO₄(Ph₂P(CH₂)₆CH=CH₂)₂ to polymerize is not due to electronic effects pertaining to the C=C unit of the Ph₂P(CH₂)₆CH=CH₂ ligand. Accordingly, steric effects are implicated in the inability of the Cp₂Mo₂CO₄(Ph₂P(CH₂)₆CH=CH₂)₂ to polymerize by ADMET.     

Methyl formation from methanol decomposition on Pd{111} and Pt{111}

The decomposition of CH₃OH adsorbed on Pd{111} and Pt{111} is compared as the surface is heated between 100 and 500 K. Using secondary ion mass spectrometry (SIMS) and thermal programmed desorption (TPD) it is suggested that an anomalous CH ₃ ⁺ ion signal observed previously by Akhter and White on oxygen precovered Pt{111} arises from the formation of a surface CH₃ species resulting from activation of the C-O bond of CH₃OH. This interpretation stems from a recent observation by Levis, Zhicheng and Winograd that CH₃OH decomposes to CH₃, OH and OCH₃ on clean Pd{111} between 100 and 300 K. The results are discussed in terms of the relative ability of these metals to synthesize CH₃OH from CO and H₂.     

Organometallic–Inorganic Conjugated Unsymmetrical Schiff-Base Hybrids. Synthesis,Characterization, Electrochemistry and X-ray Crystal Structures of Functionalized Trinuclear Iron–Nickel–Ruthenium Dipolar Chromophores

The synthesis of neutral dinuclear iron–nickel unsymmetrical Schiff base complexes 3 and 4 was achieved via a template reaction involving equimolar amounts of alkyl or aryl “half-unit” precursors, respectively, Fc–C(O)CH=C(CH₃)N(H)R (1: R = CH₂CH₂NH₂; 2: R = o-C₆H₄NH₂; Fc = CpFe(η⁵-C₅H₄); Cp = η⁵-C₅H₅), 5-bromosalicylaldehyde and nickel(II) acetate tetrahydrate in a refluxing CH₂Cl₂/MeOH (1:1) mixture. The ionic trinuclear unsymmetrical complex 5 was prepared by reacting its dinuclear precursor 3 with the arenophile source, [Cp*Ru(NCCH₃)₃]PF₆ (Cp* = η⁵-C₅(CH₃)₅), in refluxing CH₂Cl₂ for 2 h, whereas the trinuclear species 6 was formed upon regioselective π-complexation of the 5-bromosalicylidene ring of 4 by [Cp*Ru]⁺ at room temperature overnight. All the new compounds were adequately characterized by analytical and spectroscopic techniques and, in addition, the crystal and molecular structures of the “half-unit” 1, the binuclear complex 4 and its hemisolvate adduct 4 · 0.5CH₃OH, the trinuclear Schiff base compound 5 · 2(CH₃)₂CO, and the mixed sandwich metalloligand 7 have been determined by X-ray crystallography. Both organometallic–inorganic hybrids 5 and 6 contain the neutral electron-releasing ferrocenyl group, and the cationic electron-withdrawing ruthenium mixed sandwich, linked through the unsymmetrical tetradentate Schiff base complex {Ni(ONNO)}. UV–vis, ¹H and ¹³C NMR as well as electrochemical data clearly indicate a mutual donor–acceptor electronic influence between the organometallic termini. Furthermore, X-ray crystal structure analysis of 5 · 2(CH₃)₂CO reveals the partial delocalization of bonding electron density throughout the dinucleating nickel Schiff base ligand. Dedicated to Prof. Didier Astruc, a true friend, an outstanding lecturer and scientist, in honor of his pioneering research efforts and accomplishments in the fields of organometallic chemistry, dendrimers and their applications in nanocatalysis.     

Synthesis, structure, and photovoltaic property of a nanocrystalline 2H perovskite-type novel sensitizer (CH3CH2NH3)PbI3

A new nanocrystalline sensitizer with the chemical formula (CH₃CH₂NH₃)PbI₃ is synthesized by reacting ethylammonium iodide with lead iodide, and its crystal structure and photovoltaic property are investigated. X-ray diffraction analysis confirms orthorhombic crystal phase with a = 8.7419(2) Å, b = 8.14745(10) Å, and c = 30.3096(6) Å, which can be described as 2 H perovskite structure. Ultraviolet photoelectron spectroscopy and UV-visible spectroscopy determine the valence band position at 5.6 eV versus vacuum and the optical bandgap of ca. 2.2 eV. A spin coating of the CH₃CH₂NH₃I and PbI₂ mixed solution on a TiO₂ film yields ca. 1.8-nm-diameter (CH₃CH₂NH₃)PbI₃ dots on the TiO₂ surface. The (CH₃CH₂NH₃)PbI₃-sensitized solar cell with iodide-based redox electrolyte demonstrates the conversion efficiency of 2.4% under AM 1.5 G one sun (100 mW/cm²) illumination.     

Dinuclear neodymium(III) complex of cationic {12[ane]HN4(CH2CCH)4}+ with sensitized near-infrared luminescence by ion-association sensitizer

A new complex Nd₂(hfac)₆(CH₃COO)₂ {12[ane]HN₄(CH₂CCH)₄}₂ (hexafluoroacetylacetonate, hfac) was synthesized and characterized. Upon excitation of the organic cation {12[ane]N₄H(CH₂CCH)₄}⁺ (protonation on one of the nitrogen atoms of N,N′,N′,N‴-tetra-(3-prop-1-yne)-1,4,7,10-tetrazacyclododecane), the neodymium NIR luminescence is sensitized through Förster energy transfer mechanism.     

Synthesis,Characterization, and Reactivity of Lanthanide Complexes with Bulky Silylallyl Ligands

The synthesis of new lanthanide allyl complexes of enhanced stability and solubility in saturated hydrocarbons based on silyl-substituted allyl ligands is reported. Thus the potassium salt K(CH₂CHCHSiMe₃) ( 1 ) reacts with YCl₃ in tetrahydrofuran to give the tris-allyl complex Y(CH₂CHCHSiMe₃)₃ ( 2 ), while K(CH₂CHCHSiMe₂^tBu) ( 3 ) affords Y(CH₂CHCHSiMe₂^tBu)₃(THF)_1.5 ( 4 ). Slow re-crystallization of 4 from light petroleum in the presence of tert-butylcyanide led to multiple insertion to give the sec-amido complex Y{NHC(^tBu)(CH)₃SiMe₂^tBu}₂{η₂-NHC(^tBu)CH=CHCH₂SiMe₂^tBu)CH(CHCHSiMe₂^tBu)C^tBuNH}(THF)·(CH₃CH(Me)(CH₂)₂CH₃) ( 5 ), which was crystallographically characterized. The reaction of ScCl₃(THF)₃ with two equivalents of Li{1,3-C₃H₃(SiMe₃)₂} in tetrahydrofuran gives the bis-allyl complex {1,3-C₃H₃(SiMe₃)₂}₂Sc(μ-Cl)₂Li(THF)₂ ( 6 ), while the analogous reaction of K{1,3-C₃H₃(SiMe₃)₂} ( 7 ) with either LaCl₃ or YCl₃ in tetrahydrofuran affords the bis-allyl complexes MCl{1,3-C₃H₃(SiMe₃)₂}₂(THF)_x (8, M = La, x = 1; 9, M = Y, x = 0). An attempt to prepare the similar neodymium complex gave the mono-allyl complex NdI₂{1,3-C₃H₃(SiMe₃)₂}(THF)_1.25 ( 10 ). The reactions of 8 and 9 with triisobutyl aluminum in benzene-d₆ show allyl exchange between lanthanide and aluminum. Complexes 8 , 9 , and 10 have been tested with a variety of activator systems as catalysts for the polymerization of 1,3-butadiene.     

Synthesis,crystal structure and protonation of the asymmetric iron-only hydrogenase model [Fe2(CO)3(μ-pdt){μ,η2-Ph2PCH2CH2P(Ph)CH2CH2PPh2}] (pdt = SCH2CH2CH2S)

Heating [Fe₂(CO)₆(μ-pdt)] (pdt = SCH₂CH₂CH₂S) and bis(2-diphenylphosphinoethyl) phenylphosphine (triphos) in toluene gives [Fe₂(CO)₃(μ-pdt){μ,η²-Ph₂PCH₂CH₂P(Ph)CH₂CH₂PPh₂}], the major form of which has been characterised crystallographically. The complex is highly asymmetric; while one iron centre has the expected square-based pyramidal coordination environment, the second is nearer a trigonal bipyramid. In solution at room temperature, four isomers of the major form interconvert via two processes which can be frozen out at low temperature, while protonation affords a bridging hydride complex which appears to be static at all temperatures.     

Preparation of Microporous Hybrid Materials by Thermal Removal of Sterically Hindered Carbosilane Side Groups

The preparation of hybrid porous materials by condensation of poly(dimethyl-co-methyl)siloxanes functionalized with side units: i.e., templating –RC(SiMe₃)₃ [R = (CH₂)₅, (CH₂)₂SiMe₂], and reactive –Si(OEt)₃, of random distribution along the main chain is described. Tetrabutylammonium salts, tetrabutylammonium hydroxide and tetrabutylammonium fluoride were chosen as the catalytic system. The relationship between the steric hindrance of the carbosilane template, the type of n-Bu₄N⁺ catalyst and the structure of cross-linked materials was investigated. It was found that bulky carbosilane substituents can block formation of the porous structure in the cross-linked material. The type of interaction between Si(OEt)₃ and the catalyst seems to be an equally important factor for 3D structure formation. Controlled thermolysis of the cross-linked materials, performed in order to remove carbosilane units by thermal degradation, allowed for the formation of porous materials having high specific surface area.