Photofragmentation of alpha-oxocarboxylic acids in aqueous solution. An EPR study. Formation of semidione radicals by decarboxylative substitution of alpha-oxocarboxylic acids by acyl radicals--II. Oxaloacetic acid (oxosuccinic acid).

Abstract— –On in situ photolysis (Λ= 250–400 nm) of aqueous oxaloacetic acid solutions, between pH 5 and 10, the radicals ^-O₂CCH₂C(O^->=C(O⁺)CH₂CO₂^- and ^-O₂CCH₂C(OH)CO₂ are identified. With acetone present, CH₂CO₂, CH₃C(OH)CO^-₂, CH₃C(O^-)=C(O)CH₂CO₂ and -O₂CCHCOCO₂ are also observed. CO₂ and CO are identified as reaction products. The experimental results are explained in terms of α-cleavage of the electronically excited keto-isomer dianion of oxaloacetic acid to yield O₂CCH₂CO and CO₂^-. ^-O₂CCH₂CO adds to the keto-isomer of oxaloacetic acid and to pyruvic acid, which is formed from oxaloacetic acid by thermal decarboxylation, to yield ^-O₂CCH₂C(O^-)= C(O^-)CH₂C0^- and CH₃C(O^-)=C(O)CH₂CO^-₂, respectively, via a decarboxylase substitution reaction. CH₂CO₂ is derived from ^-O₂CCH₂CO by decarbonylation. CO₂^- is scavenged by oxaloacetic acid and pyruvic acid to yield O₂CCH₂C(OH)CO₂ and CH₃C(OH)CO₂^-, respectively.     

New water-soluble (hydroxymethyl)triphosphine [(HOCH2)2PCH2CH2]2PCH2OH, a derived PdII(triphosphine) complex, and triphosphine trioxide

An aqueous solution of (hydroxymethyl)triphosphine [(HOCH₂)₂P(CH₂)₂]₂PCH₂OH (II) was synthesized in situ by treatment of the triphosphine H₂P(CH₂)₂PH(CH₂)₂PH₂ with formaldehyde. Addition of a CH₂Cl₂ solution of trans-PdCl₂(PhCN)₂ to an in situ aqueous solution of II resulted in the formation of a species thought to be [PdCl{[(HOCH₂)₂P(CH₂)₂]₂PCH₂OH}]⁺Cl⁻. Attempts to isolate the complex were unsuccessful because of conversion to material containing small amounts of phosphine oxide(s) formed via a redox reaction involving water. The triphosphine trioxide [(HOCH₂)₂P(O)(CH₂)₂]₂P(O)CH₂OH was readily isolated from an in situ solution of II by treatment with aqueous H₂O₂.     

Oxalate-2-ethanolamine complexes of some bivalent cations (Mn,Co, Ni,Cu, Zn and Cd)

On the refluxing ofM(II) oxalate (M=Mn, Co, Ni, Cu, Zn or Cd) and 2-ethanolamine in chloroform, the following complexes were obtained: MnC₂O₄·HOCH₂CH₂NH₂·H₂O, CoC₂O₄·2HOCH₂CH₂NH₂, Ni₂(C₂O₄)₂·5HOCH₂CH₂NH₂·3H₂O, Cu₂(C₂O₄)₂·5HOCH₂CH₂NH₂, Zn₂(C₂O₄)₂·5HOCH₂CH₂NH₂·2H₂O and Cd₂(C₂O₄)₂·HOCH₂CH₂NH₂·2H₂O. Following the reaction ofM(II) oxalate with 2-ethanolamine in the presence of ethanolammonium oxalate, a compound with the empirical formula ZnC₂O₄·HOCH₂CH₂NH₂·2H₂O¹ was isolated. The complexes were identified by using elemental analysis, X-ray powder diffraction patterns, IR spectra, and thermogravimetric and differential thermal analysis. The IR spectra and X-ray powder diffraction patterns showed that the complexes obtained were not isostructural. Their thermal decompositions, in the temperature interval between 20 and about 900°C, also take place in different ways, mainly through the formation of different amine complexes. The DTA curves exhibit a number of thermal effects.     

The atmospheric oxidation of hydroxyacetone: Chemistry of activated and stabilized CH3C(O)CH(OH)OO• radicals between 252 and 298 K

The products of the Cl-atom-initiated oxidation of hydroxyacetone (HYAC, CH₃C(O)CH₂OH) have been examined under conditions relevant to the earth's lower atmosphere. Over the range of temperatures studied (252-298 K), in the absence of NO_x, methylglyoxal (CH₃C(=O)CH=O, MGLY) was formed with a primary yield >84% (96 ± 9% at 298 K), while in the presence of elevated NO_x, MGLY and formic acid were both formed as major primary products. In contrast to a previous study, acetic acid was not identified as a major primary product under the conditions studied. The results are quantitatively interpreted from a consideration of the formation of a stabilized CH₃C(O)CH(OH)OO• radical, either in a ≈50% yield from the addition of O₂ to CH₃C(O)CH•(OH) or in 100% yield from the addition of HO₂ to MGLY. At high temperature and low NO_x, decomposition of the stabilized CH₃C(O)CH(OH)OO• radical to MGLY is favored, while lower temperatures and conditions of high NO_x favor bimolecular reactions of the stabilized radical, with subsequent production of formic acid. Analysis of the data allows for a semiquantitative determination of K₃ = (2.9 ± 0.4) × 10⁻¹⁶ cm³ molecule⁻¹, for the HO₂ + MGLY ↔ CH₃C(O)CH(OH)OO• equilibrium process at 298 K and a roughly order of magnitude increase in K₃ at 252 K.     

Synthesis of micro- and nanosized manganese oxides from hydrated manganese oxalates and products of their chemical modification with ethylene glycol

The reactions of ethylene glycol with manganese oxalates MnC₂O₄ · 2 H₂O and MnC₂O₄ · 3H₂O on heating in air were studied. At temperature below 100°C, ethylene glycol was found to displace water from oxalates to give a new solvate compound according to the reaction MnC₂O₄ · nH₂O + HOCH₂CH₂OH = MnC₂O₄(HOCH₂CH₂OH) + nH₂O↑. The crystals of the solvates retain the morphology of the initial oxalates, which is then inherited by the products of their thermolysis. Thus, thermolysis of MnC₂O₄ · 3H₂O and MnC₂O₄(HOCH₂CH₂OH) having quasi-unidimensional structure gave Mn₃O₄ and Mn₂O₃ nanowhiskers in air and MnO in an inert gas environment. Heating of MnC₂O₄ · nH₂O in ethylene glycol at temperatures above 100°C results in anhydrous manganese oxalate.     

Photocatalytic Dissociation of CH3OH on ZnO(0001) Surface

Photocatalysis of CH₃OH on the ZnO(0001) surface has been investigated by using temperature-programmed desorption (TPD) method with a 266 nm laser light. TPD results show that part of the CH₃OH adsorbed on ZnO(0001) surface are in molecular form, while others are dissociated. The thermal reaction products of H₂, CH₃^·, H₂O, CO, CH₂O, CO₂ and CH₃OH have been detected. Experiments with the UV laser light indicate that the irradiation can promote the dissociation of CH₃OH/CH₃O^· to form CH₂O, which can be future converted to HCOO^- during heating or illumination. The reaction between CH₃OH_Znand OH_ad can form the H₂O molecule at the Zn site. Both temperature and illumination promote the desorption of CH₃^· from CH₃O^·. The research provides a new insight into the photocatalytic reaction mechanism of CH3OH on ZnO(0001).     

An energy-resolved study of the fragmentation of ionized 1-Penten-3-ol

A detailed energy-resolved study of the fragmentation of CH₂?CHCH(OH)CD₂CD₃ (1-d₅) has been carried out using metastable ion studies and charge exchange techniques, combined with collision-induced dissociation studies to establish the structures of fragment ions. At low internal energies (metastable ions) the molecular ion of 1-d₅ rearranges to the 3-pentanone structure and fragments by loss of C₂H₅ or C₂D₅ leading to the acyl structure, [CH₃CH₂C?O]⁺ or [CD₃CD₂C?O]⁺, for the fragment ion. However, with increasing internal energy of the molecular ion this rearrangement process decreases rapidly in importance and loss of C₂D₅ by direct cleavage, leading to [CH₂?CHCH?OH]⁺, becomes the dominant fragmentation reaction. As a result the [C₃H₅O]⁺ ion seen in the electron impact mass spectrum of 1-penten-3-ol has predominantly the protonated acrolein structure.     

Synthesis,electrochemical properties and fungicidal activity of 1,1′‐bis(aroyl)ferrocenes and their derivatives

Reaction of functionalized cyclopentadienyl sodium CH₃O₂CArC(O)CpNa (Ar = aryl and Cp = cyclopentadienyl) with FeCl₂ in a 2:1 ratio gives 1,1′‐bis(aroyl)ferrocenes [CH₃O₂CArC(O)Cp]₂Fe in reasonable yields. Upon treatment of these aroyl compounds with NaBH₄, the ketone carbonyl is reduced to yield compounds [CH₃O₂CArCH(OH)Cp]₂Fe, while with the stronger reductive reagent LiAlH₄, diols [HOCH₂ArCH(OH)Cp]₂Fe are obtained. All new compounds were characterized by IR and NMR spectroscopic analyses. Their electrochemical behavior was investigated by cyclic voltammetry. The structure of [CH₃O₂CC₁₀H₆C(O)Cp]₂Fe was further confirmed by single crystal X‐ray diffraction analysis. In addition, the fungicidal activities of these new compounds were also determined in vitro. Copyright © 2007 John Wiley & Sons, Ltd.     

The hydroxyl radical reaction rate constant and products of 3,5‐dimethyl‐1‐hexyn‐3‐ol

A bimolecular rate constant,k_DHO, of (29 ± 9) × 10^?12 cm³ molecule^?1 s^?1 was measured using the relative rate technique for the reaction of the hydroxyl radical (OH) with 3,5‐dimethyl‐1‐hexyn‐3‐ol (DHO, HC?CC(OH)(CH₃)CH₂CH(CH₃)₂) at (297 ± 3) K and 1 atm total pressure. To more clearly define DHO's indoor environment degradation mechanism, the products of the DHO + OH reaction were also investigated. The positively identified DHO/OH reaction products were acetone ((CH₃)₂C?O), 3‐butyne‐2‐one (3B2O, HC?CC(?O)(CH₃)), 2‐methyl‐propanal (2MP, H(O?)CCH(CH₃)₂), 4‐methyl‐2‐pentanone (MIBK, CH₃C(?O)CH₂CH(CH₃)₂), ethanedial (GLY, HC(?O)C(?O)H), 2‐oxopropanal (MGLY, CH₃C(?O)C(?O)H), and 2,3‐butanedione (23BD, CH₃C(?O)C(?O)CH₃). The yields of 3B2O and MIBK from the DHO/OH reaction were (8.4 ± 0.3) and (26 ± 2)%, respectively. The use of derivatizing agents O‐(2,3,4,5,6‐pentalfluorobenzyl)hydroxylamine (PFBHA) and N,O‐bis(trimethylsilyl)trifluoroacetamide (BSTFA) clearly indicated that several other reaction products were formed. The elucidation of these other reaction products was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible DHO/OH reaction mechanisms based on previously published volatile organic compound/OH gas‐phase reaction mechanisms. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 534–544, 2004     

Ethylene glycol-modified cobalt and iron oxalates as precursors for the synthesis of oxides as extended microsized and nanosized objects

The reactions of ethylene glycol with iron and cobalt oxalates upon heating in air are reported. Heat treatment of mixtures of oxalate powders with ethylene glycol yields new compounds (solvates) via the replacement of the water molecules in the oxalate structure by ethylene glycol molecules: MC₂O₄ · 2H₂O + HOCH₂CH₂OH = MC₂O₄(HOCH₂CH₂OH)+2H₂O↑. The crystals resulting from this reaction are elongated, and their shape is inherited by their thermolysis products. Thermolysis in air yields microwhiskers and nanowhiskers of Fe₂O₃ and Co₃O₄, and thermolysis in an inert atmosphere affords Fe₃O₄ and Co whiskers. The thermolysis of FeC₂O₄(HOCH₂CH₂OH) in helium yields a new structural modification of FeC₂O₄ as an intermediate product. The resulting compounds and their thermolysis products were characterized by X-ray powder diffraction, microscopy, IR spectroscopy, and thermogravimetric and chemical analyses. The particle shape and size were determined by scanning electron microscopy.     

Loss of methyl from [H2CC(OH)?CH3]+˙ ions prepared by electron impact ionization of unstable 2-hydroxypropene

Unstable 2-hydroxpropene was prepared by retro-Diels-Alder decomposition of 5-exo-methyl-5-norbornenol at 800°C/2 × 10^?6 Torr. The ionization energy of 2-hydroxypropene was measured as 8.67±0.05 eV. Formation of [C₂H₃O]⁺ and [CH₃]⁺ ions originating from different parts of the parent ion was examined by means of ¹³C and deuterium labelling. Threshold-energy [H₂C?C(OH)? CH₃]^+˙ ions decompose to CH₃CO⁺+CH₃^˙ with appearance energy AE(CH₃CO⁺) = 11.03 ± 0.03 eV. Higher energy ions also form CH₂?C?OH⁺ + CH₃ with appearance energy AE(CH₂?C?OH⁺) = 12.2–12.3 eV. The fragmentation competes with hydrogen migration between C(1) and C(3) in the parent ion. [C₂H₃O]⁺ ions containing the original methyl group and [CH₃]⁺ ions incorporating the former methylene and the hydroxyl hydrogen atom are formed preferentially, compared with their corresponding counterparts. This behaviour is due to rate-determining isomerization [H₂C?C(OH)? CH₃]^+˙ →[CH₃COCH₃]^+˙, followed by asymmetrical fragmentation of the latter ions. Effects of internal energy and isotope substitution are discussed.     

Theoretical Study of the Hydroxyl-Radical-Initiated Degradation Mechanism,Kinetics, and Subsequent Evolution of Methyl and Ethyl Iodides in the Atmosphere

The degradation and transformation of iodinated alkanes are crucial in the iodine chemical cycle in the marine boundary layer. In this study, MP2 and CCSD(T) methods were adopted to study the atmospheric transformation mechanism and degradation kinetic properties of CH₃I and CH₃CH₂I mediated by ⋅OH radical. The results show that there are three reaction mechanisms including H-abstraction, I-substitution and I-abstraction. The H-abstraction channel producing ⋅CH₂I and CH₃C ⋅ HI radicals are the main degradation pathways of CH₃I and CH₃CH₂I, respectively. By means of the variational transition state theory and small curvature tunnel correction method, the rate constants and branching ratios of each reaction are calculated in the temperature range of 200–600 K. The results show that the tunneling effect contributes more to the reaction at low temperatures. Theoretical reaction rate constants of CH₃I and CH₃CH₂I with ⋅OH are calculated to be 1.42×10⁻¹³ and 4.44×10⁻¹³ cm³ molecule⁻¹ s⁻¹ at T=298 K, respectively, which are in good agreement with the experimental values. The atmospheric lifetimes of CH₃I and CH₃CH₂I are evaluated to be 81.51 and 26.07 day, respectively. The subsequent evolution mechanism of ⋅CH₂I and CH₃C ⋅ HI in the presence of O₂, NO and HO₂ indicates that HCHO, CH₃CHO, and I-atom are the main transformation end-products. This study provides a theoretical basis for insight into the diurnal conversion and environmental implications of iodinated alkanes.     

Chemie polyfunktioneller Moleküle. 119 [1] Tetracarbonyl-dicobalt-tetrahedran-Komplexe mit den Liganden Bis(diphenyl-phosphanyl)amin, 2-Butin-1,4-diol und tert-Butylphosphaacetylen — Kristallstrukturanalyse des Phosphaalkin-Derivats

Chemistry of Polyfunctional Molecules. 119 [1]. Tetracarbonyl-dicobalt-tetrahedrane Complexes with the Ligands Bis(diphenylphosphanyl)-amine, 2-Butin-1,4-diol, and tert.-Butylphosphaacetylene — Crystal Structure of the Phosphaalkyne Derivative Co₂(μ-CO)₂(CO)₄(μ-Ph₂P? NH? PPh₂—P,P′) · 1/2C₆H₅CH₃ ( 4 · 1/2C₆H₅CH₃) reacts with 2-butine-1,4-diol, HOCH₂? C?C? CH₂OH ( 5 ), to the dark-red tetrahedrane complex Co₂(CO)₄(μ-η²,η²-HOCH₂? C?C? CH₂OH? C², C³) · (μ-Ph₂P? NH? PPh₂? P,P′) · THF (6 · THF). With t-butyl-phosphaacetylene, tBu? C?P ( 7 ), 4 · THF forms Co₂(CO)₄(μ-η²,η²-tBu? C?P)(μ-Ph₂P? NH? PPh₂? P,P′) ( 8 ), which also belongs to the tetrahydrane type. The compounds were characterized by their mass, IR, ³¹P{¹H} NMR, ¹³C{¹H} NMR, and¹H NMR spectra. Crystals suitable for X-ray structure analyses have been obtained for 8 from dioxane. The dark red blocks crystallize in the monoclinic P2₁/c space group with the lattice constants a = 1404,1(5), b = 1330,0(7), c = 2578,8(10)pm; β = 90,82(3)°.     

Metal‐catalyzed reversible conversion between chemical and electrical energy designed towards a sustainable society

Proton dissociation of an aqua‐Ru‐quinone complex, [Ru(trpy)(q)(OH₂)]²⁺ (trpy = 2,2′ : 6′,2″‐terpyridine, q = 3,5‐di‐t‐butylquinone) proceeded in two steps (pK_a = 5.5 and ca. 10.5). The first step simply produced [Ru(trpy)(q)(OH)]⁺, while the second one gave an unusual oxyl radical complex, [Ru(trpy)(sq)(O^?.)]⁰ (sq = 3,5‐di‐t‐butylsemiquinone), owing to an intramolecular electron transfer from the resultant O^2? to q. A dinuclear Ru complex bridged by an anthracene framework, [Ru₂(btpyan)(q)₂(OH)₂]²⁺ (btpyan = 1,8‐bis(2,2′‐terpyridyl)anthracene), was prepared to place two Ru(trpy)(q)(OH) groups at a close distance. Deprotonation of the two hydroxy protons of [Ru₂(btpyan)(q)₂(OH)₂]²⁺ generated two oxyl radical Ru‐O^?. groups, which worked as a precursor for O₂ evolution in the oxidation of water. The [Ru₂(btpyan)(q)₂(OH)₂](SbF₆)₂ modified ITO electrode effectively catalyzed four‐electron oxidation of water to evolve O₂ (TON = 33500) under electrolysis at +1.70 V in H₂O (pH 4.0). Various physical measurements and DFT calculations indicated that a radical coupling between two Ru(sq)(O^?.) groups forms a (cat)Ru‐O‐O‐Ru(sq) (cat = 3,5‐di‐t‐butylcathechol) framework with a μ‐superoxo bond. Successive removal of four electrons from the cat, sq, and superoxo groups of [Ru₂(btpyan)(cat)(sq)(μ‐O₂^?)]⁰ assisted with an attack of two water (or OH^?) to Ru centers, which causes smooth O₂ evolution with regeneration of [Ru₂(btpyan)(q)₂(OH)₂]²⁺. Deprotonation of an Ru‐quinone‐ammonia complex also gave the corresponding Ru‐semiquinone‐aminyl radical. The oxidized form of the latter showed a high catalytic activity towards the oxidation of methanol in the presence of base. Three complexes, [Ru(bpy)₂(CO)₂]²⁺, [Ru(bpy)₂(CO)(C(O)OH)]⁺, and [Ru(bpy)₂(CO)(CO₂)]⁰ exist as an equilibrium mixture in water. Treatment of [Ru(bpy)₂(CO)₂]²⁺ with BH₄^? gave [Ru(bpy)₂(CO)(C(O)H)]⁺, [Ru(bpy)₂(CO)(CH₂OH)]⁺, and [Ru(bpy)₂(CO)(OH₂)]²⁺ with generation of CH₃OH in aqueous conditions. Based on these results, a reasonable catalytic pathway from CO₂ to CH₃OH in electro‐ and photochemical CO₂ reduction is proposed. A new pbn (pbn = 2‐pyridylbenzo[b]‐1,5‐naphthyridine) ligand was designed as a renewable hydride donor for the six‐electron reduction of CO₂. A series of [Ru(bpy)_3‐n(pbn)_n]²⁺ (n = 1, 2, 3) complexes undergoes photochemical two‐ (n = 1), four‐ (n = 2), and six‐electron reductions (n = 3) under irradiation of visible light in the presence of N(CH₂CH₂OH)₃. © 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 169–186; 2009: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.200800039     

Electron ionization mass spectra of novel 2,3:4,5-bis-O-(1-methylethylidene)-β-D-fructopyranose derivatives and related sugar sulfamates

The electron-impact (EI) mass spectral fragmentation of ten bis-O- (1-methylethylidene)fructopyranose derivatives and three related sugar sulfamates were investigated. In particular, 2,3:4,5-bis-O - (1-methylethylidene)-β-D-fructopyranose sulfamate (topiramate), a potent anticonvulsant, was examined in greater detail. The fragmentation of the 2,3:4,5-bis-O-(1-methylethylidene) fructopyranose derivatives in general was not very dependent on the nature of substitution; the mechanisms of the common and unique fragmentation patterns are presented. These compounds showed characteristic peaks at m/z [M – 15]⁺, [M – 15 – 58]⁺, [M – 15 – 58 – 60]⁺, [M ? CH₂X]⁺ and [M ? CH₂X – 58]⁺ where X = OSO₂NR₂ (R ? H, CH₃, and/or Ph), OC (O)NHR, NH₂, CI and OH. The fragmentation of isomeric bis-O-(1-methylethylidene) derivatives of aldopyranose, ketopyranose and ketofuranose sulfamates was also investigated. The results indicate that isomeric sugar sulfamates can be easily distinguished in the EI mode. Key fragmentation pathways are discussed for these compounds.     

FTIR study of the Cl-atom initiated oxidation of methylglyoxal

The kinetics and mechanism of Cl-atom initiated reactions of CH₃C(O)CHO were studied using the FTIR detection method in the photolysis (λ < 300 nm) of Cl₂? CH₃C(O)CHO mixtures in 700 torr of N₂? O₂ diluent at 298 ± 2 K. The observed product distribution over the O₂ pressure range from 0–700 torr, combined with relative rate measurements, provided evidence that: (1) the primary step is Cl + CH₃C(O)CHO → HCl + CH₃C(O)CO with a rate constant of (4.8 ± 1.1) × 10^?11 cm³ molecule^?1 s^?1; and (2) the predominant fate of the primary radical CH₃C(O)CO under atmospheric conditions is unimolecular dissociation to CH₃C(O) radicals and CO, rather than O₂-addition to yield the corresponding carbonylperoxy radical CH₃C(O)C(O)OO.     

Electron transfer from α-aminoalkyl radicals to methyl viologen

The reactions of tert-butoxyl radicals with amines, leading to the formation of α-aminoalkyl radicals, and the reactions of these with the electron acceptor methyl viologen have been examined using laser flash photolysis techniques. For example, the radicals CH₃?HNEt₂ and HOCH₂?H N(CH₂CH₂OH)₂ react with methyl viologen with rate constants equal to (1.3 ± 0.1) × 10⁹ and (2.1 ± 0.4) × 10⁹M^?1 · s^?1, respectively, in wet acetonitrile at 300 K.     

Darstellung und Eigenschaften von Tris-(β-chloräthyl) phosphinoxid und Bis-(β-chloräthyl)-(chlormethyl)-phosphinoxid. 43. Mitteilung über organische Phosphorverbindungen [1]

The oxidative degradation of [(HOCH₂CH₂)₃PCH₂OH]⁺Cl^? ( 1 ) with Cl₂ yields, dependent on the pH used, either (HOCH₂CH₂)₃P?O ( 2 ) or (HOCH₂CH₂)₂ (HOCH₂) P?O ( 3 ). Chlorination of 2 and 3 with PCl₅ produces the corresponding chlorides (ClCH₂CH₂)₃P?O ( 4 ) and (ClCH₂CH₂)₂ (ClCH₂)P?O ( 5 ), respectively. Acetylation of 2 and 3 gives the corresponding esters (CH₃CO₂CH₂CH₂)₃P?O ( 6 ), and (CH₃CO₂CH₂CH₂)₂ (CH₃CO₂CH₂)P?O ( 7 ), respectively. Reaction of 7 with HBr results in the formation of (BrCH₂CH₂)₂ (BrCH₂)P?O. Nucleophilic substitution of the chlorine atoms in 4 and 5 with alkoxide or mercaptide gives e.g., 9 , 10 , 11 or 11a , while treatment with tertiary amines yields the vinyl compounds (CH₂?CH)₃P?O ( 12 ) and (CH₂?CH)₂ (CH₂Cl)P?O ( 13 ). 4 and 5 also undergo an Arbuzov type reaction with tertiary phosphites to give 14 and 15 , respectively, which on hydrolysis with conc. HCl give the corresponding acids 16 and 17 , respectively.     

Ligand‐Modification Effects on the Reactivity,Solubility, and Stability of Organometallic Tantalum Complexes in Water

Tantalum complexes [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(CH₂NMe₂)?CH)py}] ( 4 ) and [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(CH₂NH₂)?CH)py}] ( 5 ), which contain modified alkoxide pincer ligands, were synthesized from the reactions of [TaCp*Me{κ³‐N,O,O‐(OCH₂)(OCH)py}] (Cp*=η⁵‐C₅Me₅) with HC?CCH₂NMe₂ and HC?CCH₂NH₂, respectively. The reactions of [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(Ph)?CH)py}] ( 2 ) and [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(SiMe₃)?CH)py}] ( 3 ) with triflic acid (1:2 molar ratio) rendered the corresponding bis‐triflate derivatives [TaCp*(OTf)₂{κ³‐N,O,O‐(OCH₂)(OCHC(Ph)?CH₂)py}] ( 6 ) and [TaCp*(OTf)₂{κ³‐N,O,O‐(OCH₂)(OCHC(SiMe₃)?CH₂)py}] ( 7 ), respectively. Complex 4 reacted with triflic acid in a 1:2 molar ratio to selectively yield the water‐soluble cationic complex [TaCp*(OTf){κ⁴‐C,N,O,O‐(OCH₂)(OCHC(CH₂NHMe₂)?CH)py}]OTf ( 8 ). Compound 8 reacted with water to afford the hydrolyzed complex [TaCp*(OH)(H₂O){κ³‐N,O,O‐(OCH₂)(OCHC(CH₂NHMe₂)?CH₂)py}](OTf)₂ ( 9 ). Protonation of compound 8 with triflic acid gave the new tantalum compound [TaCp*(OTf){κ⁴‐C,N,O,O‐(OCH₂)(HOCHC(CH₂NHMe₂)?CH)py}](OTf)₂ ( 10 ), which afforded the corresponding protonolysis derivative [TaCp*(OTf)₂{κ³‐N,O,O‐(OCH₂)(HOCHC(CH₂NHMe₂)?CH₂)py}](OTf) ( 11 ) in solution. Complex 8 reacted with CNtBu and potassium 2‐isocyanoacetate to give the corresponding iminoacyl derivatives 12 and 13 , respectively. The molecular structures of complexes 5 , 7 , and 10 were established by single‐crystal X‐ray diffraction studies.     

Absolute rate constants for F + CH3CHO and CH3CO + O2, relative rate study of CH3CO + NO,and the product distribution of the F + CH3CHO reaction

Using a pulse-radiolysis transient UV–VIS absorption system, rate constants for the reactions of F atoms with CH₃CHO (1) and CH₃CO radicals with O₂ (2) and NO (3) at 295 K and 1000 mbar total pressure of SF₆ was determined to be k₁=(1.4±0.2)×10⁻¹⁰, k₂=(4.4±0.7)×10⁻¹², and k₃=(2.4±0.7)×10⁻¹¹ cm³ molecule⁻¹ s⁻¹. By monitoring the formation of CH₃C(O)O₂ radicals (λ>250nm) and NO₂ (λ=400.5nm) following radiolysis of SF₆/CH₃CHO/O₂ and SF₆/CH₃CHO/O₂/NO mixtures, respectively, it was deduced that reaction of F atoms with CH₃CHO gives (65±9)% CH₃CO and (35±9)% HC(O)CH₂ radicals. Finally, the data obtained here suggest that decomposition of HC(O)CH₂O radicals via C C bond scission occurs at a rate of <4.7×10⁵ s⁻¹. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 913–921, 1998