Cluster ions in the secondary ion mass spectrometry of choline and acetylcholine halides

Liquid secondary ion mass spectra of choline and acetylcholine halides exhibit several series of cluster ions whose origins were investigated using B/E and B²/E linked-scan techniques. In the case of choline halides three series of cluster ions were identified as (Me₃$ \mathop {\rm N}\limits^ + $CH₂CH₂OH + nM), (Me₃$ \mathop {\rm N}\limits^ + $CH₂CH₂OMe + nM) and (Me₃N$ \mathop {\rm N}\limits^ + $CH₂CH₂OH · Me₃$ \mathop {\rm N}\limits^ + $CH₂CH₂O^? + nM), while (CH₃COOCH₂CH₂$ \mathop {\rm N}\limits^ + $Me₃ + nM), (Me₃$ \mathop {\rm N}\limits^ + $CH₂CH₂OH + nM) and (CH₂ = CH$ \mathop {\rm N}\limits^ + $Me₃ + nM) were observed in the spectra of acetylcholine halides. For these cluster ions, bimolecular reactions induced on ion bombardment under secondary ion mass spectrometric conditions are discussed.     

Ab initio molecular orbital study on the structures and energetics of CH3OH\documentclass{article}\pagestyle{empty}\begin{document}$_{2}^{+}$\end{document}(H2O)n and CH3SH\documentclass{article}\pagestyle{empty}\begin{document}$_{2}^{+}$\end{document}(H2O)n in the gas phase

The purpose of this study was to calculate the structures and energetics of CH₃OH$_{2}^{+}$(H₂O)_n and CH₃SH$_{2}^{+}$(H₂O)_n in the gas phase: we asked how the CH₃OH$_{2}^{+}$ and CH₃SH$_{2}^{+}$ moieties of CH₃OH$_{2}^{+}$(H₂O)_n and CH₃SH$_{2}^{+}$(H₂O)_n change with an increase in n and how can we reproduce the experimental values ΔH°_n−1,n. For this purpose, we carried out full geometry optimizations with MP2/6‐31+G(d,p) for CH₃OH$_{2}^{+}$(H₂O)_n (n=0,1,2,3,4,5) and CH₃SH$_{2}^{+}$(H₂O)_n (n=0,1,2,3,4). We also performed a vibrational analysis for all clusters in the optimized structures to confirm that all vibrational frequencies are real. All of the vibrational frequencies of these clusters are real, and they correspond to equilibrium structures. For CH₃OH$_{2}^{+}$(H₂O)_n, when n increases, (1) the C O bond length decreases, (2) the C H bond lengths do not change, (3) the O H bond lengths increase, (4) the OCH bond angles increase, (5) the COH bond angles decrease, (6) the charge on CH₃ becomes less positive, and (7) these predicted values, except for the O H bond lengths of CH₃OH$_{2}^{+}$(H₂O)_n, approach the corresponding values in CH₃OH. The C O bond length in CH₃OH$_{2}^{+}$(H₂O)₅ is shorter than that in CH₃OH$_{2}^{+}$ in the gas phase by 0.061 Å at the MP2/6‐31+G(d,p) level. Except for the S H bond lengths in CH₃SH$_{2}^{+}$(H₂O)_n, however, the structure of the CH₃SH$_{2}^{+}$ moiety does not change with an increase in n. © 2000 John Wiley & Sons, Inc. J Comput Chem 22: 125–131, 2001     

Radical Ions of a Bishomobinaphthylene Containing two 1,6-methano[10]annulene moieties: An ESR and ENDOR study

The radical cation and the radical anion of ‘syn’-cyclobuta[1,2-c:3,4-c′]di-1,6-methano[10]annulene (‘syn’-4a,12a:6a, 10a-bishomobinaphthylene; 3 ) have been characterized by their hyperfine data. The highly resolved ESR spectrum of $ 3^{+ \atop \dot{}} $ is dominated by a triplet splitting from the outer pair of methano β-protons (H_o). In contrast, the ESR spectrum of $ 3^{- \atop \dot{}} $ is poorly resolved with the largest coupling constants arising from perimeter α-protons. The different hyperfine features of $ 3^{+ \atop \dot{}} $ and $ 3^{- \atop \dot{}} $ are rationalized by MO models. The SOMO of $ 3^{+ \atop \dot{}} $ ψ_SA(b₁), has substantial LCAO coefficients of the same sign at the bridged atoms C(1), C(6), C(11), and C(16), whereas in the SOMO of $ 3^{- \atop \dot{}} $, ψ_SS(a₁), the four atoms lie in the vertical nodal planes. The large width and the reluctance to saturation of the lines in the ESR spectrum of $ 3^{- \atop \dot{}} $ are attributed to the near-degeneracy of the lowest antibonding MO's. Due to their similar nodal properties, the SOMO's of $ 3^{- \atop \dot{}} $ and the radical anions of binaphthylene ( 4 ), 1,6-methano[10]annulene ( 1 ), and naphthalene ( 2 ) are interrelated. Moreover, because the cyclic π-systems in 3 and 1 deviate in the same way from planarity, the effect of such distortions on the coupling constants, a_Hμ, of the perimeter α-protons in $ 3^{- \atop \dot{}} $ and $ 1^{- \atop \dot{}} $ should be comparable. Indeed, on going from $ 4^{- \atop \dot{}} $ to $ 3^{- \atop \dot{}} $, the |a_Hμ| values are reduced exactaly by half as much as the corresponding values on passing from $ 2^{- \atop \dot{}} $ to $ 3^{- \atop \dot{}} $, of which the cyclic π-systems are twice contained in $ 4^{- \atop \dot{}} $ and $ 3^{- \atop \dot{}} $ respectively.     

Rearrangements of Radical Cations of [2.2]Paracyclophanes and of a bridged [14]annulene to those of pyrenes: An ESR and ENDOR study

ESR and ENDOR studies have been carried out on the radical cations obtained consecutively by reaction of trans-10b, 10c-dimethyl-10b, 10c-dihydropyrene ( 4 ) with AlCl₃ in CH₂C1₂. The primarily formed ${\bf 4}^{+ \atop \dot{}}$ rearranges at 253 K to the radical cation(s) of 1,6- ( 5a ) and/or 1,8-dimethylpyrene ( 5b ). At 323 K, the spectra of ${\bf 5a}^{+ \atop \dot{}}$/${\bf 5b}^{+ \atop \dot{}}$ are replaced by that of the highly persistent radical cation of 1,3,6,8-tetramethylpyrene ( 6 ). Surprisingly, ${\bf 6}^{+ \atop \dot{}}$ is also the only observable paramagnetic product resulting from a treatment of 4,5,7,8- ( 1 ), 4,7,13,16- ( 2 ), and 4,5,12,13-tetramethyl[2.2]paracyclophane ( 3 ) with AlCl₃ in CH₂Cl₂ at 353 K. The structures of the intermediates in the rearrangement [${\bf 1}^{+ \atop \dot{}}$, ${\bf 2}^{+ \atop \dot{}}$, ${\bf 3}^{+ \atop \dot{}}$] → ${\bf 6}^{+ \atop \dot{}}$ are discussed.     

Exact solution of the relativistic dynamics of a spin‐½ particle moving in a homogeneous magnetic field

The relativistic dynamics of one spin‐½ particle moving in a uniform magnetic field is described by the Hamiltonian $\mathbf{h}^{0}_{D}(\pi)=c\alpha\cdot\pi+\beta mc^{2}$. The discrete (and semidiscrete) eigenvalues and the corresponding eigenspinors are in principle known from the work of Dirac, Rabi, and Bloch. These are extensively reviewed here. Next, exact solutions are worked out for the recoil dynamics in relative coordinates, which involves the Hamiltonian $\mathbf{h}^{0}_{D}(-\mathbf{k})=-c\alpha\cdot\mathbf{k}+\beta mc^{2}$. Exact solutions are also explicitly calculated in the case where the spin‐½ particle has an anomalous magnetic moment such that its Hamiltonian is given by $\mathbf{h}_{D}(\pi)=\mathbf{h}^{0}_{D}(\pi)-\beta\mu_{\mathrm{ano}}\sigma\cdot\mathbf{B}$. Similar exact solutions are derived here when the recoiling particle has an anomalous magnetic moment, that is, the eigenvalues and eigenspinors of the Hamiltonian $\mathbf{h}_{D}(-\mathbf{k})=\mathbf{h}^{0}_{D}(-\mathbf{k})-\beta\mu_{\mathrm{ano}}\sigma\cdot\mathbf{B}$ are explicitly obtained. The diagonalized and separable form of the Hamiltonian h _D(π), written as $\tilde{\mathbf{h}}_{D}(\pi)$, has exceedingly simple forms of eigenspinors. Similarly, the diagonalized and separable form of the operator h _D(? k ), written as $\tilde{\mathbf{h}}_{D}(-\mathbf{k})$, has very simple eigenspinors. The importance of these exact solutions is that the eigenspinors can be used as bases in a calculation involving many spin‐½ particles placed in a uniform magnetic field. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 82: 209–217, 2001     

Stable γ-distonic oxonium ions: R\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^ + $\end{document}HCHR′ĊH2CHR″ and their characteristic reaction

The γ-distonic radical ions R$ \mathop {\rm O}\limits^ + $CHR′CH₂?HR″ and their molecular ion counterparts R$ \mathop {\rm O}\limits^{{\rm + } \cdot } $CHR′CH₂CH₂R″ have been studied by isotopic labelling and collision-induced dissociation, applying a potential to the collision cell in order to separate activated from spontaneous decompositions. The stability of CH₃$ \mathop {\rm O}\limits^ + $HCH(CH₃)CH₂?HCH₃, C₂H₅$ \mathop {\rm O}\limits^ + $HCH(CH₃)CH₂?HCH₃, CH₃$ \mathop {\rm O}\limits^ + $HCH(CH₃)CH₂?H₂, CH₃$ \mathop {\rm O}\limits^ + $HCH₂CH₂?HCH₃ and C₂H₅$ \mathop {\rm O}\limits^ + $HCH₂CH₂?HCH₃, has been demonstrated and their characteristic decomposition, alcohol loss, identified. For all these γ-distonic ions, the 1,4-H abstraction leading to their molecular ion counterpart exhibits a primary isotope effect.     

Theoretical study of synthetic reaction of tetrazole and tetrazolate anion

Tetrazole (H₂CN₄) and tetrazolate anion (HCN$_{4}^{-}$) are high‐energy compounds with a five‐membered ring‐type structures, which can be easily synthesized by HCN and HN₃ and by HCN and N$_{3}^{-}$, respectively, in an irreversible reaction. The ab initio methods including MP2/6‐31G**, B3LYP/6‐31G**, B3LYP/6‐311+G(2d,p), and CBS/QB3 from Gaussian 98 program are employed to study the thermochemistry and reaction mechanism. The transition states of both HCN + HN₃ → H₂CN₄ and HCN + N$_{3}^{-}$ → HCN$_{4}^{-}$ reaction are investigated, and it is found that the latter reaction is more favored than the former one in view of the chemical kinetics and thermodynamics, thus indicating that tetrazole (H₂CN₄) and tetrazolate anion (HCN$_{4}^{-}$) are formed more easily in an alkali environment than in other systems. Pentazole (HN₅) is an unknown high‐energy compound and has not yet been synthesized. For comparison, HN₅ and N$_{5}^{-}$, both which have similar type of synthetic reactions to the above‐mentioned reactions, are studied. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 80: 27–37, 2000     

Einelektronen-Redoxreaktionen von 4-(1-Pyridinio)phenolat-Betain: ESR/ENDOR-Charakterisierung seiner Radikalionen und ‘Batterie-Effekt’

One-Electron Redox Reactions of 4-(1-Pyridinio)phenolate Betaine: ESR/ENDOR Characterization of its Radical Ions and ‘Battery Effect’ Blue zwitterionic 2,6-Di(tert-butyl)-4-(2,4,6-triphenyl-1-pyridinio)phenolate 1a can be reduced to its blue-green radical anion ${\bf 1}^{- \atop \dot{}}$ using alkaline metals, and oxidized to its colorless radical cation 1 by Ag(OOCCF₃) or electrochemically. ESR/ENDOR spectra of their aprotic THF solutions indicate predominant spin population either in the pyridinium (${\bf 1a}^{- \atop \dot{}}$) or in the phenolate ring (${\bf 1a}^{+ \atop \dot{}}$). Reduction with other alkaline metals Li, Na, or Cs yields no changes in the ESR/ENDOR signal patterns, i.e. provides no indication of radical ion pair formation. The cyclovoltammetrically determined first reduction and oxidation potentials at ?1.11 V and +0.26 V, respectively, are both reversible and, in principle, allow to construct a molecular battery.     

Base Hydrolysis of Pentaaminecobalt(III) Complexes: The [CoX(dien) (dapo)]n+ system. Part 1. Syntheses,structures, configuration,and spectroscopy

Oxygentation of aqueous solutions of Co^III in presence of stoichiometric amounts of N-(2-aminoethyl)ethane-1,2-diamine (dien) and 1,3-diaminopropan-2-ol (dapo) produces μ-peroxocobalt(III) dimers. Acid cleavage (HCI) yields mer-exo(H)-, mer-endo (H)-, unsym-fac-exo(OH)-, and unsym-fac-endo(OH)-[CoCl(dien)(dapo)]²⁺ ( A–D )(X = Cl), resp. and unsym-fac-[Co-(dien)(dapo-N,N′,O)]³⁺ ( G ). Isomer seperation was achieved by fractional crystallization as ZnCl and ClO salts and by ion-exchange chromatography. The corresponding bromo, azido, nitrito-O, nitro-N, thiocyanato, hydroxo, and aqua complexes were also synthesized. Optically resolved samples were prepared for chiral compounds, and the complexes were structurally characterized by X-ray analyses ($ \mathop {\it \Lambda} \limits^ \to $(?)_436(CD) -A (X = N₃)), ($ \mathop {\it \Delta} \limits^ \to $(?)₄₃₆(CD) -B ). (X = N₃), $ \mathop {\it \Delta} \limits^ \to $ (+)₄₃₆(CD) -B by their chiroptical properties, and by ¹³C-NMR spectroscopy supported by ¹H-NMR, IR, CD, and UV/VIS spectroscopy. $ \mathop {\it \Lambda} \limits^ \to $(?)_436(CD)-mer-exo(H)-[Co(N₃)(dien)(dapo)](hydrogen di-O-benzoyl-L-tartrate)₂.4 H₂O crystallizes in the orthorhombic space group P2₁2₁2₁, a = 7.676(1) Å, b = 19.457(1) Å, c = 34.702(2) Å. $ \mathop {\it \Lambda} \limits^ \to $(?)_436(CD)-mer-endo(H)-[Co(N₃)(dien)(dapo)] (hydrogen di-O-benzoyl-L-tartrate)₂.2.75 H₂O crystallizes in the triclinic space group P1, a = 8.062(3) Å b = 10.296(1) Å, c = 15.056(2) Å, alpha = 80.55(1)°, β = 85.18(2)°, γ = 89.10(2)°. $ \mathop {\it \Delta} \limits^ \to $(+)_436(CD)-mer-endo(H)-[Co(N₃)(dien)(dapo)](hydrogen di-O-benzoyl-L-tartrate)₂. 5.75 H₂O crystallizes in the triclinic space group P1, a = 7.742(1) Å, b = 10.014(1) Å, c = 18.045(2) Å, α = 99.57(1)°, β = 92.87(1)°, γ = 102.56(1)°. The absolute configurations of the three cations were determined unambiguously. Interconversions of the various isomers and derivatives and structural, configurational, and spectroscopic aspects are discussed in detail.     

Direct and Reverse Limiting Series of Transition Metal Phosphides with Ordered Defects and Metal/Non Metal Ratio Close to 2

Two new limiting series of ternary compounds with ordered defects have been evidenced, which crystallize with hexagonal symmetry, space group P6m2. The first one (direct series) shows one metal vacancy and corresponds to the chemical formula □R T X . The compounds α‐UCr₆P₄ (n = 0) and Zr₄Co₁₃Si₉ (n = 1) are the first members of the series. X‐ray single crystal determination and/or electron microprobe analysis confirm the ternary phosphides Ce₉Ni₂₅P₁₃ and Ce₁₆Ni₃₆P₂₂ to be the following members. The second family (reverse series) with chemical formula R□ T X comprises the ternaries α‐UCr₆P₄ (in fact member n = 0 in both series) and UMo₁₃P₉ (n = 1), the structure of which has been determined on a single crystal. The limiting structures to which the two series converge have been found to be YbPtP (direct) and WC (reverse). The structural relationships between the direct and reverse series have been discussed in terms of metal vacancies and coordination polyhedra. Moreover, a general crystal chemical rule has been established that permits prediction of the different members for the two series and their structural definition in terms of lattice parameters, atomic coordinates and theoretical X‐ray diffraction patterns. Finally, this rule permits to give for each member the number of metal vacancies as well as the distribution of the metalloid polyhedra occupied by the metal atoms (trigonal prisms, pyramids, tetrahedra, triangles).     

The Radical Anions and Trianions of 1,8-Diphenylnaphthalene and of Some of its Derivatives Containing a Cyclophane Substructure

The radical anions of 1,8-diphenylnaphthalene ( 1 ) and its decadeuterio-(D₁₀- 1 ) and dimethyl-( 2 ) derivatives, as well as those of [2.0.0] (1,4)benzeno(1,8)naphthaleno(1,4)benzenophane ( 3 ) and its olefinic analogue ( 4 ) have been studied by ESR and ENDOR spectroscopy, At a variance with a previous report, the spin population in \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{-\kern-4pt {.}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {2}^{-\kern-4pt {.}} $\end{document} is to a great extent localized in the naphthalene moiety. A similar spin distribution is found for \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {3}^{-\kern-4pt {.}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {4}^{-\kern-4pt {.}} $\end{document}. The ground conformations of \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{-\kern-4pt {.}} $\end{document}-\documentclass{article}\pagestyle{empty}\begin{document}$ \rm {4}^{-\kern-4pt {.}} $\end{document} are chiral of C₂ symmetry. For \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{-\kern-4pt {.}} $\end{document}, an energy barrier between these conformations and the angle of twist about the bonds linking the naphthalene moiety with the phenyl substituents were estimated as ca. 50 kJ/mol and ca. 45°, respectively. The radical trianions of 1 , D₁₀- 1 , and 2 , have also been characterized by their hyperfine data. In \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{3-\kern-4pt {.}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {2}^{3-\kern-4pt {.}} $\end{document}, the bulk of the spin population resides in the two benzene rings so that these radical trianions can be regarded as the radical anions of ‘open-chain cyclophanes’ with a fused naphthalene π-system bearing almost two negative charges. The main features of the spin distribution in both \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{-\kern-4pt {.}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{3-\kern-4pt {.}} $\end{document} are correctly predicted by an HMO model of 1 .     

The gas phase ion chemistry of the acetyl cation and isomeric [C2H3O]+ ions. On the structure of the [C2H3O]+ daughter ions generated from the enol of acetone radical cation

Methods are described for the unequivocal identification of the acetyl, [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document} ?O] (a), 1-hydroxyvinyl, [CH₂?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? OH] (b), and oxiranyl, (d), cations. They involve the careful examination of metastable peak intensities and shapes and collision induced processes at very low, high and intermediate collision gas pressures. It will be shown that each [C₂H₃O]⁺ ion produces a unique metastable peak for the fragmentation [C₂H₃O]⁺ → [CH₃]⁺+CO, each appropriately relating to different [C₂H₃O]⁺ structures. [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}?O] ions do not interconvert with any of the other [C₂H₃O]⁺ ions prior to loss of CO, but deuterium and ¹³C labelling experiments established that [CH₂?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? OH] (b) rearranges via a 1,2-H shift into energy-rich leading to the loss of positional identity of the carbon atoms in ions (b). Fragmentation of b to [CH₃]⁺+CO has a high activation energy, c. 400 kJ mol^?1. On the other hand, , generated at its threshold from a suitable precursor molecule, does not rearrange into [CH₂?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? OH], but undergoes a slow isomerization into [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}?O] via [CH₂\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}HO]. Interpretation of results rests in part upon recent ab initio calculations. The methods described in this paper permit the identification of reactions that have hitherto lain unsuspected: for example, many of the ionized molecules of type CH₃COR examined in this work produce [CH₂?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? OH] ions in addition to [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}?O] showing that some enolization takes place prior to fragmentation. Furthermore, ionized ethanol generates a, b and d ions. We have also applied the methods for identification of daughter ions in systems of current interest. The loss of OH^˙ from [CH₃COOD]^+˙ generates only [CH₂?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? OD]. Elimination of CH₃^˙ from the enol of acetone radical cation most probably generates only [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}?O] ions, confirming the earlier proposal for non-ergodic behaviour of this system. We stress, however, that until all stable isomeric species (such as [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^{\rm + } $\end{document}?C:]) have been experimentally identified, the hypothesis of incompletely randomized energy should be used with reserve.     

The radical anion of 1,2:9,10-dibenzo[2.2]paracyclophane.. An ESR,ENDOR, and TRIPLE resonance study

The radical anion of 1,2:9,10-dibenzo[2.2]paracyclophane ( 3 ) has been studied by ESR, ENDOR, and TRIPLE resonance spectroscopy under a variety of experimental conditions. The coupling constants of the eight protons in the deck-benzene rings, and of the four inner and four outer protons in the side-benzene rings are 0.234, 0.123, and 0.036 mT, respectively (solvent: 1,2-dimethoxyethane; counterion: K⁺). All three values have the same sign which is predicted to be negative. Comparison of the largest coupling constant (0.234 mT) with the corresponding value (0.297 mT) for the radical anion of the parent [2.2]paracyclophane ( 1 ) points to similar nodal properties of the singly occupied orbitals in and . Notwithstanding this similarity, seems to associate less readily than with alkali metal counterions, since tight ion pairs of with K⁺ are formed only in solvents of low solvating power. Effects of conformational changes on the ESR spectra, such as those previously observed for the radical anion of [2.2]paracyclophane-1,9-diene ( 2 ), are not apparent for in the temperature range of investigation. Hyperfine data are also reported for the radical anion of a derivative 4 which has a CH₃ substituent in one of the side-benzene rings of 3 .     

Acyl- und Alkylidenphosphane. XXXIV [1]. Methoxycarbonylphosphane – Verbindungen aus dem Umfeld des Phosphaalkins PC?O?Li(dme)2

Acyl- and Alkylidenephosphanes. XXXIV. Methoxycarbonylphosphanes – Compounds closely related to the Phosphaalkyne P?C? O? Li(dme)₂ Whereas methyl fluoroformate reacts with an equimolar amount of bis(tetrahydrofuran)lithium bis(trimethylsilyl)phosphanide ( 1a )

1 Die Numerierung des betreffenden Lithiumphosphanids wird um das Suffix a erweitert, wenn von einer Röntgenstrukturanalyse her Gehalt an koordinierendem Solvens und Konstitution bekannt sind. Nach Möglichkeit beziehen wir uns dann im Text und in den Gleichungen auf derartige Spezies.

in 1,2-dimethoxyethane to give an inseparable mixture of tris(methoxycarbonyl)- ( 3 ) and tris(trimethylsilyl)phosphane, colourless crystals of lithium bis(methoxycarbonyl)phosphanide-1,2-dimethoxyethane (2/3) ( 4a ) are isolated in 84% yield from an analogous reaction with (1,2-dimethoxyethane- O,O ′)lithium phosphanide ( 2a ) in a molar ratio of 2:3. When, however, this ratio is changed to 1:2 or 1:1, the ³¹ P nmr spectra of those solutions show the formation of the by-product lithium methoxycarbonylphosphanide ( 10 ) or methoxycarbonylphosphane ( 6 ) respectively. The function of phosphanide 10 as an important intermediate in the synthesis of the phosphaalkyne P?C? O? Li(dme) ₂ ( Ia ) [1] is discussed in detail. With trifluoroacetic acid in 1,2-dimethoxyethane the diacylphosphanide 4a is converted via a lithium-hydrogen exchange into bis(methoxycarbonyl)phosphane ( 9 ). Unlike 1,3-diketones and other diacylphosphanes [25], solutions of this compound do not show the presence of an enol tautomer even in very unpolar solvents. Tris(methoxycarbonyl)phosphane ( 3 ) obtained in a pure state from methyl chloroformate and phosphanide 2a , might decarboxylate to give the corresponding bis(methoxycarbonyl)methyl derivative 5 when the reaction mixture is worked up. ³¹P and characteristic ³¹C nmr data of these methoxycarbonylphosphanes and their related lithium phosphanides are compared with each other, the tris(phenoxycarbonyl) ( 7 ) and the bis(methoxycarbonyl)phenyl compound 8 being included. An x-ray structure determination (P1 ; a 715.8(2); b = 899.5(1); c = 1262.7(2)pm; α = 99.93(1)°; β = 96.01(1)°; γ = 104.81(1)° at ?100±3°C; Z = 1 dimer; wR₂ = 0.152) shows lithium bis(methoxycarbonyl)phosphanide-1,2-dimethoxyethane (2/3) ( 4a ) to crystallize as a centrosymmetric neutral complex. Either lithium square pyramidally coordinated is bound to both carbonyl oxygen atoms of an almost planar bis(methoxy-carbonyl)phosphanide {Li? O_av. 197.4; O ‥ O 280.9} as well as of an 1,2-dimethoxyethane ligand (210.3; 261.6) and is brigded by another solvent molecule (204.0 pm). Further characteristic average bond lengths and angles are as follows: P$ \ddot - $C 179.5; C$ \ddot - $O 122.2; C? O 136.5; O? CH₃ 143.2 pm; C$ \ddot - $P$ \ddot - $C 98.8°; P$ \ddot - $C$ \ddot - $O 132.5°; P$ \ddot - $C? O 107.9°.     

Mechanism of the hydroxyiodination of 2-butenoic acid

Aqueous iodination of trans-2-butenoic acid proceeds via hydrolysis of I₂ to form HOI and I^?, then rapid addition of HOI across the double bond to form the iodohydrin product. In the presence of iodate to keep iodide concentration low, the reaction proceeds at a conveniently measurable rate. The rate for the addition reaction is ?d[C₄H₆O₂]/dt = 5900 [H⁺][C₄H₆O₂][HOI]M/s at 25.0°C when [IO] = 0.025M and ionic strength = 0.3. The overall rate law in the presence of iodate is where [H⁺] and [IO] are total concentrations used to prepare the solution.     

Density functional theory study of the structures and stabilities of CuO\documentclass{article}\pagestyle{empty}\begin{document}$_{3}^{-}$\end{document} and CuO3

Hybrid density functional theory calculations on the structures, vibrational frequencies, electron binding and dissociation energies, and bonding properties of CuO$_{3}^{-}$ and CuO₃ species have been carried out. Stable isomers containing an O₃ subunit and composed of O₂ bound to CuO have been located on the potential energy hypersurfaces of CuO$_{3}^{-}$ and CuO₃. The isomers formed by O₂ bonded to CuO in side‐on and end‐on coordination are more stable than those containing an O₃ subunit. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 162–168, 2001     

The Radical Cations of Bicyclo[2.2.1]hepta-2,5-diene (8,9,10-Trinorborna-2,5-diene) and bicyclo[2.2.2]octa-2,5-diene (2,3-Dihydrobarrelene). An ESR and ENDOR study

The radical cation of bicyclo[2-2.1]hepta-2,5-diene (8,9,10-trinorborna-2,5-diene; 1 ) in CF₂ClCFCl₂, and CF₃CCl₃ matrices and that of bicyclo[2.2.2]octa-2,5-diene (2,3-dihydrobarrelene; 2 ) in CFCl₃ and CF₃CCl₃ matrices have been studied by ESR and ENDOR spectroscopy. For ${\bf 1}^{+ \atop \dot{}}$, the coupling constants of the olefinic, methano-bridge, and bridgehead protons are ?0.780 ±0.005, +0.304±0.002, and ?0.049±0.002 mT, respectively. The hyperfine tensor for the methano-bridge protons is axial, A_x = +0.263 ± 0.002 and A_y = +0.386 ± 0.002 mT, while that for the olefinic protons is orthorhombic, A_x = ?0.594 ± 0.005, A_y= ?0.913 ± 0.005, and A_z = ?0.834 ± 0.005 mT (x parallel to C? H- z parallel to 2p_π axis). For ${\bf 2}^{+ \atop \dot{}}$, the coupling constants of the olefinic, ethano-bridge, and bridgehead protons are ?0.68 ± 0.01, +0.162 ± 0.005, and ?0.108 ± 0.005 mT, respectively. The hyperfine data for ${\bf 1}^{+ \atop \dot{}}$ and ${\bf 2}^{+ \atop \dot{}}$ fully support the presentation of their singly occupied orbitals as antisymmetric combinations, b₂(π), of the two bonding ethene π-MO's.